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Ramsey - FX-50 User manual - The Repeater Builder`s Technical

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1. 1 8 2 pf C49 1 15 pf C80 4 22 pf C15 17 31 43 5 27 pf C21 22 52 63 82 1 39 pf C87 1 56 pf C51 2 82 pf C20 27 7 100 pf may be marked 100 or 101 C26 30 35 39 54 64 76 1 100 pf chip capacitor C72 1 120 pf C12 1 150 pf C103 1 220 pf C28 RRRERRRRRRRRR FX50 53 ADDITIONAL DISC CAPACITORS 16 001 uf may be marked 001 102 or 1nf C1 2 3 4 10 23 24 56 62 66 71 77 83 86 88 89 26 01uf may be marked 01 103 or 10 nf C11 16 18 25 33 36 37 38 44 45 46 47 50 53 55 57 59 61 69 78 79 84 9 7 98 99 104 2 047 uf C68 91 10 1 uf may be marked 1 or 104 C5 6 8 9 13 14 41 58 65 85 ELECTROLYTIC Polarized CAPACITORS 2 2 uf electrolytic C67 C70 C90 C92 4 7 to 10 uf electrolytic C7 48 93 95 96 100 101 102 47 uf electrolytic C40 220 uf electrolytic C60 330 uf electrolytic C29 470 uf electrolytic C34 1500 uf electrolytic C42 RRRRRRR gt x lt m D RESISTORS 2 ohm red black gold R108 15 ohm brown green black R36 51 ohm green brown black R8 12 28 29 30 100 ohm brown black brown R10 23 34 105 119 220 ohm 1 2 watt red red brown R32 45 54 This resistor may range from 200 to 240 ohms 270 ohm red violet brown R9 17 18 20 58 470 ohm yellow violet brown R21 63 64 2 1K ohms brown black red R2 3 15 19 65 68 69 70 113 114 115 2 2K ohms red red red R42 57 61 4 7K ohms yellow violet red R111 112 3 3K ohms orange orang
2. ES 1 Make sure a 1 amp fuse is installed in the fuse holder 2 Connect the fused and black wires to a 12 volt battery or power supply 12 15 volts DC Connect the black lead of a DC voltmeter or VOM to the ground plane of the PC board Study the PC board and locate the points marked 12V 8V and 5V NOTE The 5V test point is located at the front of the board near the diode matrix These connections are provided for convenience in later modifying or experimenting With the power switch turned on you should get meter readings of 12V 8V and 5V If your meter probe does not have a fine enough point to make solid contact inside the holes at these 3 points simply study the multi color PC board illustration and look for 12 8 and 5 volts DC on PC board traces that lead to the 2 voltage points After you are satisfied that the power input circuitry is working correctly disconnect the 12 volt source WIRING THE PACKET I O CONNECTION amp S A12 Press J1 the Packet I O DIN connector into position Before soldering make sure that the bottom of the jack is perfectly flat against the board It is best to solder only the middle pin first check for straightness and then solder the other 4 or 6 points DIN jack styles may vary your jack may have simply the 5 connector pins or 2 extra pins for mechanical stability Either style fits your PC board Directions for installing hardware or unusual parts often r
3. 1 1 1 1 1 1 0 0 0 0 0 0 0 0 1 1 1 1 Oo oo OI o o o o lololjo o a4 a a Ay Ay Ay ay Ay Sy oe Oo oo oO Oo oO OI O oOo oOo O oo gt mY mY Sy k Ss Ss Sy aM aa a ol ol oil olj ol o ol ol OF ol OF ojl leads simply press them into place and solder both ends If the 100K 53 99 10 798 1 0 resistors are supplied in the more usual style of a taped strip all you need to Other Simplex Frequencies do is work out your own mass production procedure to get the resistors in place as illustrated There is no right better or best way other than the need 32490 m Meek 9 oF cn N for clean soldering practice 52 510 10 502 1 0 0o 61 0 0 00 0 1 H11 21 a Install the 14 100K resistors brown black yellow required for R91 R101 and R116 118 Plan careful soldering procedure and install the parts FX 50 104 FX 50 29 RAMSEY FX series Programming Worksheet To convert N from decimal to binary simply TRY to subtract EACH of the 16 binary values from N always in descending order always starting with 32768 and always ending with 1 This process will always yield 16 YES or NO answers which will give you exact diode installation instructions N Freq in KHz divided by 5 KHz or Freq in MHz divided by 005 Let s try doing an example We want to receive 52 525 MHz N 52525 5 10 505 Now convert to binary Subtracting from N R
4. 336 IF NM lt 4 THEN NX NM 340 IF NX gt 2 THEN OO 1 345 IF NN 2 THEN OO 1 346 IF NX 3 THEN PP 1 347 IF NX 1 THEN PP 1 400 PRINT 32768 AA 405 PRINT 16384 BB 410 PRINT 8192 CC 415 PRINT 4096 DD 420 PRINT 2048 EE 7 425 PRINT 1024 FF Notice that the values of the highest 6 positions are the same throughout the 430 PRINT 512 GG band We still must program in those six positions but we only need to 435 PRINT 256 HH ini 440 PRINT 128 II calculate for the remaining 10 512 through 1 445 PRINT 64 JJ Let s look again at the programming of 52 525 MHz Simplex where N 450 PRINT 32 KK 10 505 First we see that the 8K position is always programmed with a PRN a Kn ae 460 PRINT 8 MM diode and that the 32K 16K and 4K positions never have a diode installed 465 PRINT 4 NN Let s put that fact to practical use 470 PRINT 2 OO f a aes 475 PRINT 1 PP 1 We will always install a diode in the 8K position This gives us an initial N value of 8 192 480 PRINT The Binary Equivalent of N can also look like this 481 PRINT 2 This number can be used to START programming ANY 482 PRINT USING AA BB CC DD EE FF GG HH II JJ KK LL MM NN OO PP frequency within the Amateur 6 Meter Band We need only add 485 PRINT additional diodes in the 2048 through 1 positions for
5. Stage CR ASSEMBLY PROCEDURE CR1 Install U1 the MC13135 24 pin DIP FM Receiver IC Make sure all 24 pins are visible through the holes before soldering Be very sure that the notched end is oriented as illustrated Install the following resistors CR2 Install R11 47K ohm yellow violet orange CR3 Install R5 10K ohm brown black orange CR4 Install R4 68K ohm blue gray orange CR5 Install R24 10K ohm brown black orange CR6 Install R9 270 ohm red violet brown CR7 Install R3 1K ohm brown black red CR8 Install C16 01 uf disc capacitor marked 01 103 or 10nf CR 9 Install C5 1 uf marked 1 or 104 RO ROR O AB ie SB It fits only one way This is the 6 pole ceramic 455 KHz IF filter network Verify that filter FL2 is properly seated and soldered FX 50 72 CR10 Select and install FL2 the rectangular plastic block with 3 thin pins STAGE A DC POWER INPUT REGULATION amp DISTRIBUTION and PACKET RADIO I O CONNECTOR J1 The power supply for your FX transceiver is basically any 12 volt battery or well designed power supply operating from 120VAC or other source In theory all 12V sources should provide pure DC voltage to your FX transceiver DC input In fact there are many variations and imperfections in common 12VDC sources ranging from weak batteries poorly filtered AC powered supplies vehicle ignition noise or just badly made power supplies Stage A of your FX Tra
6. controlled compared with another frequency as is done in a PLL circuit See PHASE DETECTOR PLL RSSI Received Signal Strength Indicator a function of the MC13135 IC and comparable circuits which permits MEASURING of the relative strength of a received signal A few microamps of variation can be interpreted as DB decibels of signal strength RX Abbreviation for receive receiver receiving See TX SPEAKER MIKE speaker and microphone functions contained in the same physical housing as in the design of simple home intercoms For ham operators this means that both speaker and microphone are in a microphone casing with separate plugs from a common cord Since such accessories can use ANY style of plug for either mic or speaker function Ramsey Electronics has adopted the popular COM compatible standard for the FX transceivers SHIELD The outer braid of audio or RF coaxial cable or the aluminum case enclosing a coil or transformer The metal case of a transceiver also performs an important RF shielding function The shield blocks or protects a coil from the effect of nearby objects that would change its inductance The shielding on cable prevents the inner wire from radiating RF or from picking up stray radiation such as AC hum SQUELCH means literally to subdue utterly or crushingly In radio communication usually VHF and UHF squelch is the circuitry needed to subdue mute the background noise until a detected signal
7. good time to sort and organize all your picofarad capacitors ranging in value from 2 to 100 pf Correct selection of these values will be essential throughout the RF stages of your transceiver Re ROO oh RO Bo RR ORo Ne B O N a es ama R CR11 Install C9 1 uf marked 1 or 104 CR12 Install C8 1 uf CR13 Install C13 1 uf marked 1 or 104 CR14 Install C14 1 uf CR15 Install C102 10 uf electrolytic Check polarity CR16 Install C6 1 uf CR17 Install C7 10 uf electrolytic Watch polarity or U1 s audio won t reach U2 CR18 Install C10 001 uf marked 001 or 102 CR19 Install C15 22 pf marked 22 CR20 Install C12 120 pf marked 121 CR21 Select and install Y1 the 21 855 MHz crystal It must be snug on the board before soldering Be sure not to confuse Y1 with Y2 the 10 240 MHz crystal which will set the Reference Frequency for the PLL Synthesizer or with FL1 which has 3 leads CR22 Install L1 the 455 KHz shielded coil marked LB53303HK Make sure it is seated squarely on the board before soldering Solder all pins CR23 Install C101 10 uf electrolytic capacitor CR24 Install R6 3 3K ohm orange orange red CR25 Install R8 51 ohm green brown black CR26 Install R2 1K ohm brown black red CR27 Install R1 470K ohm yellow violet yellow CR28 Install Q1 NPN type 2N3904 Before soldering press the transistor as far into its holes as possible with the flat side
8. illustrated for vertically installed parts Always put the body of the part in the hole with the circle 9 Whenever you have a choice install parts with stamped markings so that you can still see the markings later This will help greatly with any possible troubleshooting needed 10 PARTS SORTING In a kit of this size and complexity there is no single best way to sort and organize the 300 individual components used We FX 50 56 Stage DR Antenna Input and RF Preamplifier The operation of the FM receiver IC was discussed in Stage CR The purpose of the following circuitry is to minimize the strength of unwanted signals and to boost signals in the 50 54 MHz range before they reach the 1st mixer input of U1 pin 22 In addition the circuit includes PIN diodes for proper T R transmit receive switching Let s follow the signal path briefly from the antenna jack remembering that the antenna is picking up thousands of signals from all over the radio spectrum Capacitors C20 26 27 28 30 and L2 L3 form a low pass filter suppressing unwanted signals that are higher than the desired receiving range The filtered signals are coupled through C47 to Q3 a low noise preamp stage and then on to a band pass filter network consisting of C17 22 49 31 52 and L4 and 5 For use in very high RF environments an optional helical filter may be installed in place of this band pass filter Helical filters provide excellent filtering ch
9. let s take another look at the whole circuit in a more formal way The PLL Frequency Synthesizer IC MC145152 incorporates the equivalent of 8000 individual transistors and contains the following circuits A crystal reference oscillator governed by Y2 10 24 MHz A counter or frequency divider circuit set externally to divide the crystal oscillator output by 2048 for a Reference Frequency output of 5 KHZ A second counter or frequency divider that divides the frequency from the Prescaler U3 by the externally programmed number that we call N A third frequency divider A also used for programming Control logic circuitry which permit the N and A counters to work together for channel programming FX 50 91 l DIVIDE BY DMDE BY N DIVIDE BY A 64 65 i PRESCALER PROGRAMMING FREQUENCY SYNTHESIZED Inserted into this circle is the frequency synthesizer U6 with U3 which compares the output of the VCO with the output of its own 10 24 MHz Reference Oscillator see Y2 and also with the frequency programming which you have set up After making these comparisons it gives an instruction to the VCO in the form of a precision voltage applied to the varactor diodes and the cycle repeats itself at lightning speed Try dividing 10240 KHz by 2048 on your calculator If you get an answer of 5 KHz you are correct and perhaps on your way to seeing how the FX transceiver can be programmed in 5 KHz steps If you are curi
10. side rails 7 There is no point in securing the front panel controls and jacks to the panel permanently until AFTER wiring the Channel Selection switch Note the locking hole for the switch in the front panel which mates the tab on the front of the switch 8 Use care and a well chosen pair of pliers to secure the microphone and speaker jacks to the front panel so as not to scratch the panel 9 Bend the leads of the TX LED so that their tension presses the front of the bulb against its front panel hole 10 Whenever you find it necessary to remove the top shell store the screws back into their holes in the side rails 11 If you decide to install a ribbon cable in the diode matrix for external programming control route the cable folded at a right angle on the synthesizer and receiver side of the board so that it exits the case between the rear panel and top cover right above the DC power cord Do NOT route any such cable across the VCO and transmitter side 12 After the PC board is secured to the case bottom and front rear panels it is a good idea to neaten up the wires to the controls and jacks bundling them at two or three points with tie wraps or cord FX50 13 GUIDE TO PC BOARD I O CONNECTIONS In addition to primary interconnections required for jacks and controls etc your FX series Transceiver PC board provides additional access to operating voltages and circuit features to make later customizing as neat and
11. specialized applications requiring only the basic PC board kit We try whenever we can to accommodate that important do it yours elf spirit of ham radio ENCLOSURE KIT PARTS LIST Please check the boxes after the components have been identified and it is also handy at this time to sort the like components into groups or bins an egg carton does nicely to avoid using the wrong component during assembly Steel bottom shell with 5 threaded PC board standoff posts Steel top shell Front control panel Rear panel with access holes to PC mounted jacks Steel side rails PC board standoff spacers 4 nuts to secure PC board on standoffs 4 screws to mount front and rear panels 6 screws for securing top and bottom to side rails large knob for Channel Selection Switch smaller knobs for Volume and Squelch controls self adhesive rubber feet RRRERRRRRRRRR AN MMHONMA22 AH CFX CASE ASSEMBLY PROCEDURE The purpose of these hardware parts is largely selfevident We offer the following suggestions for your convenience and to minimize wear and tear on your factory fresh CFX enclosure 1 Since the bottom shell might be used for several test fittings during transceiver assembly install the rubber feet right away to protect its finish 2 Obviously the PC board cannot be secured permanently to the bottom section until after installation of L9 R32 and L10 AFTER Alignment and before Transmitter tuneup 3 Install the s
12. 1X23 C60 220 uf electrolytic capacitor observe correct polarity X24 C58 1 uf marked 1 or 104 TX25 C59 01 uf TX26 Locate and install L13 the 1 1 2 turn coil previously wound in step TC3 TX27 C55 01 uf marked 01 103 or 10 nf X28 C63 27 pf marked 27 or 27K X29 Trimmer capacitor C74 TX30 C64 100 pf FX 50 119 TX1 Install Q9 RF NPN type 2N3866 Let it rest flush on the round bare area of the board The holes match the pins so the tab will point exactly as illustrated TX2a RF Final transistor Q8 MRF237 or SD1127 is also installed completely flush on the board with the tab oriented toward L9 The case of Q8 is common to the emitter Be sure the case stays completely flat against the top ground plane when soldering the 3 points READ CAREFULLY The following procedure lets the top groundplane serve as the heatsink for the RF final output transistor Do not be hesitant in making a smooth solder bond between Q8 s case and the board An ordinary soldering pencil tip applied to both the case and the groundplane at the same time will NOT damage Q8 On the other hand the lack of a good heatsink bond WILL destroy Q8 when transmitting This procedure is INTENDED by the manufacturer TX2b Now using only your regular soldering pen and NOT a soldering gun solder the rim of Q8 directly to the top ground plane starting at the square tab Use enough solder for thorough bon
13. LM358 dual op amp IC Be certain to orient the notched end as pictured on the PC board OBSERVE CORRECT POLARITY FOR THESE CAPACITORS A A RA A RAR R G10 Install C70 2 2 uf electrolytic G11 Install C67 2 2 uf electrolytic G12 Install C96 4 7 or 10 uf electrolytic G13 Install C90 2 2 uf electrolytic G14 Install C92 2 2 uf electrolytic G15a Insert U7 type 74HC283 IC with its notched end correctly oriented Solder the 4 outermost pins G16a Insert and solder U8 as in step G15a FX 50 94 FX SERIES TRANSCEIVER GLOSSARY The following is a deliberately INFORMAL collection of Technical terms useful to know in understanding your FX transceiver design Acronyms phrases expressed by first letters of words example PLL Phased Locked Loop Selected Electronics Industry jargon Any of these words or expressions might be used in this instruction manual or in conversation related to your FX transceiver either with other hams or with Ramsey technicians These descriptions or notes for a very few terms certainly are not an electronics dictionary but the author compiler hopes that they might enhance your grasp of the concepts and language that he has seen as useful in building and using this transceiver For more detail PLEASE study the introductory part of each Assembly Stage ADDER Anybody who can add can be called an adder If we delegate such work to electronic devices the most fu
14. Modulation Changing the transmitter frequency in exact pace with speech or sound variations FREQUENCY SYNTHESIS To synthesize anything is to create an imitation or simulation from something else The basic ways for generating useful RF frequencies are a crystal oscillator or the L C oscillator where the frequency is determined by coil L and capacitor C However we can process the output of an L C oscillator through digital circuitry to simulate many different precise crystal like frequencies using only one crystal as a reference standard See also PLL PHASE DETECTOR VCO FSK Frequency Shift Keying TRUE FSK actually moves the RF frequency transmitted and received from one pre determined point to another in contrast to AFSK Audio Frequency Shift Keying where the transmitted signal remains steady and all shifting is done by audio tones GROUND PLANE ALL sections of a PC board which are mechanically or electrically connected to DC and RF ground In the Ramsey FX design almost ALL of the top or upper side component side of the board is a groundplane The term is also used in antenna design if your 2M or 1 25M antenna has a vertical radiating element plus four or more horizontal elements connected FX 50 40 Unlike simpler PLL IC s U6 s phase detector has TWO outputs at pins 7 and 8 These outputs go through very simple low pass filters R44 C68 R53 C91 to cut back the 5 KHz whine sound of U6 at work Op am
15. N gt 32768 THEN NA N 32768 206 IF N lt 32768 THEN NA N 210 IF NA gt 16384 THEN BB 1 215 IF NA gt 16384 THEN NB NA 16384 216 IF NA lt 16384 THEN NB NA 220 IF NB gt 8192 THEN CC 1 225 IF NB gt 8192 THEN NC NB 8192 226 IF NB lt 8192 THEN NC NB 230 IF NC gt 4096 THEN DD 1 235 IF NC gt 4096 THEN ND NC 4096 236 IF NC lt 4096 THEN ND NC 240 IF ND gt 2048 THEN EE 1 245 IF ND gt 2048 THEN NE ND 2048 246 IF ND lt 2048 THEN NE ND 250 IF NE gt 1024 THEN FF 1 255 IF NE gt 1024 THEN NF NE 1024 256 IF NE lt 1024 THEN NF NE 260 IF NF gt 512 THEN GG 1 265 IF NF gt 512 THEN NG NF 512 266 IF NF lt 512 THEN NG NF 270 IF NG gt 256 THEN HH 1 275 IF NG gt 256 THEN NH NG 256 276 IF NG lt 256 THEN NH NG 280 IF NH gt 128 THEN II 1 285 IF NH gt 128 THEN NI NH 128 286 IF NH lt 128 THEN NI NH 290 IF NI gt 64 THEN JJ 1 295 IF NI gt 64 THEN NJ NI 64 296 IF NI lt 64 THEN NJ NI 300 IF NJ gt 32 THEN KK 1 305 IF NJ gt 32 THEN NK NJ 32 306 IF NJ lt 32 THEN NK NJ 310 IF NK gt 16 THEN LL 1 315 IF NK gt 16 THEN NL NK 16 316 IF NK lt 16 THEN NL NK FX 50 32 Can we subtract 2048 from 2313 2313 2048 265 Can we subtract 1024 from 265 Can we subtract 512 from 265 Can we subtract 256 from 265 265 256 9 Can we subtract 128 from 9 Can we subtract 64 from 9 Can we subtract 32 from 9 Can we subtract 16 from 9 Can we subtract 8 f
16. The J1 Packet I O port can be quickly connected to many modern TNC s and the Ramsey P IBM or P64 Packet Modems with Radio Shack s shielded DIN cable 42 2151 Otherwise your first step is to prepare a reliable 5 conductor cable with a 5 pin DIN plug RS 274 003 at one end and the correct connector needed by your packet TNC at the other end If you salvage a ready made 5 pin DIN cable from something like a discarded computer joystick be sure that there are indeed 5 wires or at least the ones that are required by your TNC Z Ady 96 1 BS X4 SOINOMIOTTA LISNVY Lybdbabdlsds G Consult your Packet TNC or Packet Modem documentation for ALL details on hookup and operation Pin 4 of J1 offers a choice of amplified and squelched speaker level audio output or low level discriminator output This choice is set up by the jumper wire positions clearly visible on the PC board Packet RX Audio Jumper Some TNC s require low level audio from the discriminator output of the FM detector while others will accept soeaker output Either is available in the FX transceivers Simply install a jumper in the appropriate location near VR1 to connect EXT AUDIO to either SPKR for speaker audio or DATA for discriminator audio Use scrap E resistor wire to make the jumper You also can choose to wire these three Ba os points to a miniature SPDT switch which you can mount on the rear panel R104 5g d a near the packet connector OR use a PC mount sw
17. Transmit TP1 For checking of VCO control voltage during alignment TP2 For checking VCO frequency with counter TP3 For checking U3 prescaler output with counter 3 OPTIONS 12V GND 8V 5V 8T 8R provide supply voltage for accessories or modifications designed by you 8T and 8R are near L9 and U4 Jumper Options for Packet Operation SPKR to EXT AUDIO Speaker level audio for packet J1 DISC to EXT AUDIO FM discriminator output for packet COR Carrier Operated Relay output from U1 Binary Programming Holes The row of holes alongside the Binary Programming labels permits installation of ribbon cable for external programming devices designed by the innovative amateur radio community switches or interfaces or a row of internal DIP switches FX 50 15 MICROPHONE amp SPEAKER INFORMATION The FX transceivers with the hardware supplied are designed to accept standard ICOM or ICOM compatible speaker mikes such as MFJ 284 Ramsey sells the SM 7 speaker mike the perfect companion to your FX kit Another conveniently available such unit is Radio Shack No 19 310 Be aware that the receiver audio amplifier is capable of supplying a husky 2 watts or more of audio power and will drive full size communications speakers to excellent volume levels The PTT switching circuit can be activated simply by introducing a resistance e g 10K from the microphone input to ground This resistance is enough to trigger the PTT
18. as above wind a 1 1 2 turn coil for L13 It will appear to be 2 turns if viewed from the top 2 5 TURN 1 5 TURN The legs or leads for inserting these coils should be 1 4 long The coil should sit 1 16 maximum above the PC board groundplane Keep these coils handy for later installation FX 50 114 FX 50 CIRCUIT OVERVIEW The FX 50 VHF FM Transceiver circuit theory is explained in progressive stages and in some detail as part of our Learn As You Build approach to electronic kits Builders are encouraged to study and learn about a stage or section build it and then test it before going to the next stage The circuit explanations are necessarily written for people with all levels of experience starting with and FAVORING beginners Following is a straight and minimally chatty synopsis or overview of FX series technical information provided in the building stages However we ll still follow the same stage by stage designations of the building process A DC Power Input Much of the circuitry operates on the regulated 8 volts supplied by voltage regulator VR1 8R or 8T are points where the regulated 8V output is switched for Receive or Transmit by the PTT circuitry Q12 U4c U4d Q13 Q14 The Receiver IC U1 and the digital frequency synthesis circuit are powered by 5 volts regulated by VR2 The op amps used in the circuit U4 and U5 operate from this single supply through the use of voltage divider networks at the
19. audio See Test Procedure FX 50 124 DC POWER SUPPLY CONSIDERATIONS Your Ramsey FM Transceiver is designed to operate from any stable DC voltage source in the 12 to 15 volt range from typical car boat or plane 12V systems to a wide variety of battery packs or AC powered DC sources Ina pinch you can get on the air for quite a while with 8 to 10 ordinary D cells Our lab tests show only a 93 amp current draw for 5 watts of RF output We have just a few points of advice and caution 1 Your DC supply should be able to provide a minimum of 1 0 amperes in continuous service Any battery setup capable of supplying 12 15VDC will serve quite well Use of wall plug power supplies is NOT recommended Obviously 12VAC output is not suitable Most DC output units do not have adequate voltage regulation 4 Turn your transceiver OFF before re starting the vehicle in which it has been installed Replace F1 only with a 1 amp fuse If you power your transceiver from the 12V accessory voltage available from other equipment be sure that source is rated for the 1 amp required 7 Your transceiver circuit includes noise suppression at the DC input and additional filtering at the VCO primarily to prevent ignition alternator noise from being introduced into the FM modulation If you hear ignition noise in the receiver the vehicle has a serious general problem Check your transmitted signal on another receiver before mobile operation R
20. but such a test is not essential at this point Simply connect a utility test amp to PL press the mike button and talk FX50 113 M18 Install Q11 NPN transistor type 2N3904 Be sure to orient flat side as shown M19 Identify and install R46 the yellow color modulation control trimmer potentiometer It differs from trimmer capacitors by having three terminals Simply place it in position and solder all three points NOTE The remaining three transistors used in this section are PNP types 2N3906 or similar marked 228256 It is essential to use the correct transistor type for Q12 Q13 Q14 M20 Install Q12 PNP transistor type 228256 Orient flat side as shown M21 Similarly install Q13 PNP type 228256 M22 Install Q14 PNP type 228256 Install the following additional parts M23 R60 near Q12 10K brown black orange M24 R62 also 10K brown black orange M25 R111 near Q13 4 7K yellow violet red M26 R40 100K brown black yellow M27 R63 470 ohms yellow violet brown M28 R64 also 470 ohms yellow violet brown M29 R112 4 7K yellow violet red M30 R39 near Q11 47K yellow violet orange Be I BOR Be Be Ro M31 Install diode D11 1N914 1N4148 Orient the banded end as shown M82 Similarly install diode D12 another 1N914 1N4148 IMPORTANT The following parts are located in areas of the PC board that have already been assembled If the ham in you pursued an assembly
21. circuit is internal to U1 the crystal is Y1 21 855 MHz The 455 KHz second IF output pin 7 requires filtering We used a precision ceramic 455 KHz filter with 6 poles for a 2nd IF filtering scheme designed to solve the adjacent frequency swamping effect experienced with many handhelds costing much more The receiver has good hysteresis characteristics the ability to hold the squelch open once it has been broken by a marginal signal even if the signal becomes weaker The squelch is activated by signal strength not by noise R13 permits squelch adjustment Finally the carrier detect circuitry affords the same COR Carrier Operated Relay action as needed in any repeater which is why the output of pin 16 is also available on the PC board designated COR Stage DR Antenna Input and RF Preamplifier At Antenna jack J3 C20 26 27 28 30 and L2 3 form a low pass filter The filtered signals are coupled through a pin diode T R switch to Q3 a 2SC2498 favored for its high gain and low noise 18 db gain 9 db noise figure Front end components C17 L4 C27 L5 C49 C52 and C31 form a BANDPASS filter which sets both upper and lower limits on the RF passing from Q3 to Q2 for further amplification and coupling via C78 to U1 pin 22 The PIN diodes D2 D6 and D7 perform all RF T R functions PIN diodes can pass RF energy either way when turned on by DC voltage and also block RF from the other direction when not powered by
22. circuit without interfering with the microphone audio input Consider these factors in selecting microphone speaker and or speaker mike for FM voice operation If your microphone and speaker preferences differ radically from the use of a speaker mike and you do not wish to alter the front panel remember that you also have very easy access to mike and speaker lines via J1 the packet connector A FEW ANTENNA CONSIDERATIONS The idea of building your own transceiver is to save money and enjoy your hobby Effective VHF and UHF antennas are easy and inexpensive to build whether for fixed or mobile use There are plenty of off the shelf antennas to buy but don t hesitate to roll your own If you are a newcomer to ham radio you ll discover many strong opinions about the best antenna to use A home built ground plane vertical or even a dipole can provide very satisfying results Whether you need a gain factor or directivity in your antenna depends on your operating goals Regardless of the style of antenna it really pays to give serious attention to electrically solid weatherproof connections of the coaxial cable to the antenna elements A simple antenna in good condition will outperform a fancy one that s been neglected Popular ham magazines and ARRL publications provide plenty of antenna building ideas MFJ Enterprises offers good value in simple ready to use antennas for 6 Meters FX 50 16 Stage TX Transmitter Buffer Drive
23. coming from each end A5 Install C42 1500 uf the first and largest of the electrolytic capacitors The side must be oriented as imprinted on your board toward L20 A6 Install C95 a 4 7 to 10 uf electrolytic Observe correct polarity for all electrolytic capacitors NOTE The silkscreen for C95 is marked ref des on your PC board C95 is between VR1 and C42 A7 Select D18 the 1N4002 the largest of the diodes used in your kit It has a black body with a gold band on one end Notice the band towards one end designating the cathode This diode MUST be installed with its ANODE in the ground hole nearest the back of the PC board Solder the anode end now letting the diode body stand vertically on the board A8 Gently bend the cathode wire into its hole pull it through so that it is as short as possible with the diode standing vertically Solder and trim excess wire NOTE this is the basic method for installing all upright parts AQYa Voltage Regulator VR1 type 7808 for 8 volts is mounted with its metallic back flat against the ground plane secured by the small machine screw and nut supplied Identify VR1 correctly without mixing it up with its 5 volt counterpart VR2 AQb Insert the 3 VR1 leads into the triangular set of holes while gently bending the body back towards the board so that the mounting holes line FX 50 62 2 The First IF converts the incoming 52 525 MHz signal down to 21 4 MHz In order to do thi
24. core solder Correct tools for all phases of assembly see text Microphone and speaker per specifications in text U2 J4 and PTT circuit are designed for COM type mike Fused 13 5 VDC power supply or battery 50 ohm dummy load 50 ohm 2 meter antenna with PL259 or adapter OPTIONAL RECOMMENDED Ramsey CFX Transceiver Case and Knob Kit RRR RRR IMPORTANT For proper RF shielding and secure mounting of controls connectors and the PC board immediate consideration must be given to the transceiver enclosure as an integral part of the assembly process The CFX matching case set is the quality custom designed finishing touch for your transceiver FX 50 55 VERY IMPORTANT PC BOARD ASSEMBLY INFORMATION FOR A L L OUR BUILDERS 1 Your FX transceiver PC board is double clad with plated through holes What this means in practice is that it is VERY important to select and install correct part values the FIRST time around This type of board makes desoldering much more difficult and risky because the solder adheres inside the hole and flows to the component side of the board as well It is VERY tricky to remove a part without damaging it If too much de soldering heat or component pulling is used there is also the serious risk of damaging small PC board traces Be careful and methodical in assembly 2 Do not under any circumstances install L9 R32 or L10 until instructed to do so in Assembly Stage TX This applies ev
25. diode D18 largest black body gold band 1 6 2 volt zener diode 1N5234 D23 gray body with black band R ROO BOR FX 50 52 Stage E F The FX Transceiver VCO The VCO Voltage Controlled Oscillator provides basic frequency control for both transmit and receive modes It is essential to understand its function in the transceiver circuit Q7 is the oscillator transistor and the key VCO components are L7and D3 Think of the VCO for now as just a simple VFO type RF oscillator whose output frequency can be changed by adjusting the slug in L7 Notice that there are no capacitors either fixed or variable to form a tuned circuit with L7 Instead varactor diode D3 performs this function A varactor diode changes capacitance in step with the amount of voltage applied across it If the output of this simple oscillator reaches U1 through C35 you would certainly be able to receive any signals on a frequency determined by that oscillator frequency plus or minus 21 4 MHz the Receiver 1st IF Similarly if the oscillator output could reach Q9 and Q8 in the transmit section or even the transmit buffer Q10 some sort of signal could be put on the air After the VCO is assembled on the PC board the interested builder has the option of experimenting with it in receive mode before proceeding The VCO must be capable of considerable frequency range To receive a signal at 50 MHz the VCO must tune to 50 MHz minus 21 4 MHz or 28 6 MHz To
26. either give up a standard split or devise your own way of switching in what you need TX RPT OFFSETS TX offsets are programmed exactly like the Frequency Programming matrix For example for a 1 0 MHz offset N 1000 KHz 5 KHz 200 Therefore install diodes at the 128 64 and 8 positions See Stage H for instructions and detailed examples PROGRAMMING THE MINUS OFFSETS We showed the Plus offsets first to prepare you for the Minus offsets The offsets are entered into the FX synthesizer through the binary adders U7 10 Notice that we said adders and not subtractors in binary there is no such animal as a subtractor We must use the technique known as two s complement addition which actually performs a subtraction process This may sound complicated but it really isn t We simply find N as usual take its two s complement and program the result into the offset matrix We ll show you three detailed examples Don t be alarmed If all you need is the standard 6 Meter band offsets just install the diodes in the offset matrix as clearly illustrated on your PC board Understanding the following information is essential ONLY for those who need to program non standard Minus or AUX offsets First we need to understand some rules for binary addition 1 0 0 0 2 1 0 1 3 1 1 0 and CARRY 1 Carrying is done from right to left EXAMPLE 1 1 0 MHz TX Offset As for the 1 0 MHz offset N 1000 5 KHz 200 However t
27. for the RPT line 8 16 32 256 512 1K 2K 4K 8K REMEMBER position cathode banded ends down zs TO4 For 1 0 MHz TX offset install 3 diodes in the RPT line 8 64 128 FX50 115 Assembly Stage TC Transmitter Coil amp RF Choke Preparation A few parts need handmade preparation before installation in the transmitter RF stages of your transceiver We recommend that you get them ready for installation before wiring the Driver and Final stages If you prefer to proceed with those stages winding coils as you go that s fine too as long as you realize that all coil making details are provided in this section The wire used for this is the tinned bus wire supplied with your kit If you mess up you can get a whole 50 spool of it from Radio Shack 278 1341 TC1 WINDING L12 and L14 Use the heavier gauge wire in your kit for these coils the same wire that was used to make the diode programming bridges Wind these two coils on the threads of the 5 16 X 18 bolt to assure perfect forming of the coils You wondered what that big bolt was for didn t you Each coil is 2 1 2 turns and will appear to have 3 turns if viewed from the top Study the PC board silkscreen to help you visualize them TC2 Winding L2 and L3 Using the same wire and 5 16 bolt wind two 7 1 2 turn coils for L2 and L3 They appear to be 8 turns if viewed from the top TC3 WINDING L13 Using the same wire and process
28. in the following pages You indeed have the freedom to solder first and read all about it later We hope though that you ll take it easy learning as you build and then enjoy the reliability of your Ramsey FX Transceiver for a long time to come The style of our kit building directions presumes that you are peeking at our multi color parts layout sheet while seeing that the very same parts outlines are imprinted on the component side of your FX PC board Our smaller kits do not justify any need for on board imprinting silk screening Therefore such kits provide more detailed published explanations for identifying correct locations for inserting and soldering parts You ll install EVERY FX part perfectly by using our simple step by step kit building process And you ll know the WHY of most assembly steps if not all of them Before you start THINK about what you ll create from those bags of FX 50 6 FX 50 TECHNICIAN S NOTES Throughout production of the FX series transceivers the technicians here at Ramsey have been speaking with customers making repairs experimenting and compiling notes on the FX 50 These notes and the circuit overview and theory of operation sections of your FX 50 manual provide extensive information on the inner workings of the FX 50 Should a nasty gremlin jump into your trusty new FX 50 this information will help lead your foray into troubleshooting Several voltages and testpoints are given thr
29. is because they are sold mainly to engineers and designers for prototyping A blank metal enclosure even slightly comparable to the CFX case kit will run 30 to 80 or more Even a plain aluminum chassis box cover will be around 15 00 B If you think there s any chance you someday may wish to sell or trade your transceiver you should be aware that units mounted in odd boxes may have even less value than the bare circuit board with documentation alone C Many distributors have a minimum mail order of 25 00 D Your best chance for finding an inexpensive alternative case is to have access to a lot of ham friends who tend to collect stuff or to browse the catalogs or showrooms of electronic surplus dealers You just might find a gorgeous new box originally intended for somebody s ingenious Ultra Modem external disk drive or other dream gadget from two years ago Are we trying to discourage you No not really We know you can see that there are good reasons to consider calling Ramsey Electronics and getting your CFX case on its way while you work on the PC board and PLL Programming However we do not want you to feel stuck with our recommended CFX enclosure so we have worked up a detailed shopping list for getting what you will need to make as attractive a finished unit as possible with a single trip to the neighborhood Radio Shack store FX 50 10 R TX36 Install R41 1K brown black red TX37 Install D4 1N914 1N4148 d
30. now wing it on your own observing the way we are mounting the connector to our case If you are using the Ramsey CFX case set mount the SO 239 to the rear panel as part of this assembly operation Use the two screws and four nuts supplied and consult the illustration as needed The flange of the connector sits on the outside of the rear panel Mount the connector with one set of nuts then mount the low pass filter PC board using the other two nuts Solder the connector center pin to the board FX 50 123 9 Disconnect power and proceed with completing the transmitter section Steps TX15 etc IMPORTANT If you do not achieve the test results discussed above there is no point in doing more work on the transmitter section until the problem is solved If you are not able to transmit at least within the same room and receive on any desired frequency finishing the transmitter is not going to fix the problem CONTINUE TRANSMITTER ASSEMBLY TX33 Install RF choke L10 one of the pre wound 8 turn enameled wire coils TX34 Install L9 the other 8 turn pre wound coil TX35 Install L2 one of the 7 1 2 turn coils you hand wound in step TC2 Sit it above the PC board about 1 16 Stage TX FINAL PROGRESS CHECK 1 Double check component selection for Steps TX 2 Use bright light and magnifier to go over entire board to check for missed connections or solder bridges If you suspect a solder bridge simple review the X ra
31. oriented as illustrated CR29 Install FL1 the 21 4 MHz IF filter Its 3 wires may be inserted either way make sure its body is snug against the top of the board before soldering FX50 73 ADDITIONAL RECEIVER IC FUNCTIONS AND FEATURES In addition to audio output at pin 17 a separate high speed data output up to 35000 baud is available and may be linked directly to a packet TNC or other data controller using the jumper wire pad provided on the PC board The MC13135 is capable of detecting true FSK frequency shift keying in addition to AFSK The receiver has good hysteresis characteristics the ability to hold the squelch open once it has been broken by a marginal signal even if the signal becomes weaker The IC also has carrier detect circuitry which is put to good use in the transceiver design by providing very effective squelch action The squelch is activated by signal strength not by noise When no carrier is detected the voltage at pin 16 is high which causes Q6 to mute the audio amplifier U2 as explained in Stage B When a carrier is detected the voltage at pin 16 drops low turning off Q6 Resistor R13 permits squelch adjustment Finally the carrier detect circuitry affords the same COR Carrier Operated Relay action as needed in any repeater which is why the output is also available on the PC board designated COR It is up to creative users to determine their own practical implementations for this feature
32. precision adjustment of C81 requires either a frequency counter connected to TP2 or a digitally accurate VHF receiver tuned to 52 525 MHz With the microphone keyed button pressed C81 is adjusted for exactly 52 525 MHz on your Ramsey frequency counter or a zero beat 52 525 MHz signal on a digitally accurate monitoring receiver If you cannot tune C81 high enough clip out C80 15 pf An adequate initial adjustment of C81 can be made by listening to your signal on any VHF FM receiver and carefully adjusting C81 for the clearest sounding signal Or adjust C81 for the best reception of a transmitted signal of known accuracy This might be all that you ll ever need to do but it is recommended that you make the precise adjustment when possible 8 While speaking in the microphone adjust modulation level R46 for the best sounding speech Best is not necessarily the maximum see the following note NOTE R46 adjusts the FM deviation of the transmitted frequency Deviation is carrier frequency swing in step with voice modulation If you over deviate your signal will not be stronger Instead the speech will become distorted and splash over to adjacent channels Deviation is a very important adjustment best sounding speech will usually result in the proper 5KHz deviation used on VHF FM FX 50 121 TX31 L8 2 2 uh choke green body with red and gold bands TX32 D7 BA482 PIN diode small glass body marked BA482 Observe c
33. sequence different from these step by step directions you may already have soldered in these parts If so no ham is done Be certain now though that the following are installed M833 R107 10K ohms brown black orange M34 Diode D22 type 1N914 or 1N4148 near VR1 Orient the banded end correctly 8T through R107 and D22 turns on Q6 to mute the audio amp IC during transmit M35 C62 near Modulation pot R46 001 uf M36 R35 100K brown black yellow FX 50 112 Stage CR Integrated FM Receiver The MC13135 is a complete FM narrowband receiver from antenna input pin 22 to audio output pin 17 The low voltage dual conversion design results in low power drain excellent sensitivity and good image rejection in narrowband voice and data link applications The FX 50 implementation of this IC yields increased image rejection by using a 21 4 MHz first IF rather than the traditional 10 7 MHz A precision 2 pole crystal filter FL1 is used for the 21 4 MHz first IF Our design injects the PLL controlled VCO output through C35 to pin 2 rather than using U1 s internal local oscillator circuit The VCO input to pin 2 is mixed with the RF input from the antenna circuitry The first mixer amplifies the signal and converts this RF input to 21 4 MHz This IF signal is applied to the second internal mixer via pin 18 where the 2nd IF frequency of 455 KHz is achieved by mixing with the 21 855 MHz oscillator The oscillator
34. sharper in science and math This Learn as You Build approach to electronics hobby kits is now evident in all Ramsey Electronics build it yourself kits from our under 5 student kits up to this synthesized VHF transceiver suitable for ham radio and public service applications alike We think that learning and UNDERSTANDING as we build is especially essential in a more sophisticated project such as the Ramsey FX series VHF transceivers In fact we are so convinced of this basic need that this kit instruction manual departs from the traditional scheme of separating assembly directions from a theory of operation The FX series of Ramsey VHF UHF Transceivers puts today s FM 2 way radio technology back in YOUR hands at a budget price Our idea of budget looks far beyond the modest purchase price to our goal that you can maintain your FX unit in good operating readiness with no need for expensive shop service On the other hand we also have made the transceiver design as abuse proof and rugged as possible Alignment traditionally an intimidating many steps process is very easy quick and fool proof in this circuit design Instead of separate stage by stage assembly directions plus separate theory information these FX instruction booklets highlight your transceiver s operational theory often a single component at a time with actual construction steps provided as follow up after each explanation The assembly sequences are easy to find
35. subtract 4 from 4 YES Therefore diode at 4 4 4 0 This 1 5 MHz TX offset is set up easily by diodes at 256 32 8 and 4 Programming of Minus offsets is covered in the Reference section of your manual ADDITIONAL CIRCUIT NOTES The 19 100K resistors at the frequency programming matrix and the 14 100K resistors at the offset matrix are called pull down resistors and are required to ensure positive logic switching action of U6 Transistor Q15 and its associated switching diodes ensure that the desired offset is switched in during transmit that offset programming does not interfere when simplex is desired and that the offsets do not interfere with receiver operation and that receiver programming 21 4 MHz lower does not interfere with transmit operation Obviously these simple parts must be installed correctly or major PLL problems would result Note The silkscreen on your PC board may contain diode placement markings that differ from your calculated placement Always follow your calculated placement and ignore the silkscreen which could contain errors FX 50 103 THE RX TX OFFSET PROGRAMMING MATRIX Diode placement in this matrix follows the same binary number principles as used for frequency programming This matrix is connected to the 16 programming inputs of U6 through the four binary adders U7 U10 Fewer programming positions are provided on the board simply because there is no practical use for extremely larg
36. supply of simple single conductor hookup wire Use the heavier gauge wire for the power supply connections in the following steps saving the lighter gauge wire for jacks and controls The bare wire is used for constructing the diode matrix for frequency programming and for making a few coils and RF chokes TINNING is the process of heating the stripped end of a wire and LIGHTLY flowing solder so that all strands are bonded together This practice while not essential generally makes for easier soldering and physically stronger connections BROKEN WIRES are the primary cause of malfunctions in ham equipment and computers Please follow our instructions in Stage CR PAGE 27 for securing completed cables to the PC board temporarily so the connections will not get damaged during further assembly IMPORTANT NOTE REGARDING FLEXING WIRES In Stages A B CR and M you will install numerous wires from the PC board for panel controls and jacks Repeated flipping of the board during assembly can damage these wires and also become very annoying during kit assembly PLEASE tie the wires down as noted on page 27 using one of the cable ties provided Take your time learn about what you re doing and ENJOY your FM Transceiver project FX 50 58 FX SERIES TRANSCEIVER Simplified Receiver Block Diagram ANTENNA LOW PASS FILTER HIGH PASS FILTER 21 885 MHz LOCAL OSCILLATOR LIMITER FM DISCRIMINATOR AUDIO AMPLIFIER Q3 B
37. the various a a channels within the band 520 END 3 We determine these additional diodes by the same Descending Attempted Subtraction that we used above for studying the programming of 52 525 MHz Simplex a process which you can do in your head with scratchpaper or on the FX 50 Programming Worksheet Let s do an example 1 We re already familiar with the right answer for 52 525 simplex let s use it again N 52525 5 10 505 2 Since we have already installed a diode in the 8K position our initial N is 8 192 The N we need is 10 505 3 We now figure the difference between the N needed and the initial N 10 505 8 192 2 313 4 Now using the Attempted Subtraction technique find the remaining binary value to be programmed FX 50 100 FX50 33 Here s an example of the screen display for the program as written showing the results for an entry of 146865 and ready for the next frequency to be entered as 6 digits For example 146 52 MHz 146520 Enter here gt gt gt 146865 The FX146 or FX220 N number for binary conversion is 29373 32768 0 16384 8192 4096 2048 1024 512 256 128 POORER ROR ORFOORHH te gt gt The Binary Equivalent of N looks like this 0111001010111101 gt gt gt Enter Next Frequency for Programming Enter Receiver Frequency as 6 digits with NO decimal For example 146 52 MHz 146520 Enter here gt gt gt HOW TO ACTIVATE
38. they are put there BK Starting with the easiest add up the values for the 3 diodes used in the RPT line 128 64 8 200 200 X 5 KHz 1 0 MHz which is added by U10 and U9 to the frequency programmed on the main matrix To say it precisely 200 is added in binary form to the binary form of the N number FX 50 102 Using Computer BASIC as a Diode Matrix Programming Aid The purpose of the following BASIC program is to be as CLEAR AND GENERIC as possible with no concern for programming efficiency or sophistication Those who enjoy and understand programming in Basic can dress it up to suit themselves Or they can write a program that satisfies their own standards A major purpose of the deliberate simplicity is that the routine should run on virtually any computer using any version of Basic If you follow the program flow you ll see that it carries out in order the very same steps you would follow by hand in converting decimal to binary using the FX Programming Worksheet You can use this same program for calculating nonstandard Transmitter Offsets Program Notes 1 Install diodes ONLY in rows where 1 is indicated 2 If you prefer 0 s can also be generated through the use of appropriate IF THEN ELSE lines 3 The after 32768 is generated automatically by the computer whether you type it in or not 4 Be VERY accurate in typing lt and gt or gt because they are critical to correct placeme
39. to 60 Mhz as seen on TP2 If not check area of Q7 TP3 should indicate approx 1 64 of the frequency at TP2 If not check area of U3 Common faults Solder shorts between traces Diodes installed in reverse Excess lead length on VCO components 9 Improper frequency readings Try probing on other components Q7 Q16 R113 for a better reading 2 VCO Frequency Incorrect a If frequency is incorrect on one channel only recheck diode programming for that channel c A few channels are off by the same amount Check for similar diode programming on these channels to find your faulty area ex Let s say our faulty channels are all off by 10 Khz and they all use the 2 diode programming position Hmmm if we refer back to the manual isn t our n number for 10 Khz right about 2 Some coincidence Now we can guess that our fault is between the 2 position trace and the input to U6 FX 50 128 SPECIFICATIONS FOR THE RAMSEY FX 50 General Frequency Range Tuning Programming Transmit Offset Mode Packet Data Operation Packet RX Audio Power Requirement Power Consumption Antenna Impedance Microphone Impedance T R switching PTT circuit Semiconductors Transmitter Final Power Output Final Output Stage Modulation Max frequency deviation Modulation distortion Receiver Circuitry Sensitivity Selectivity Squelch sensitivity Audio output Circuit access po
40. 0 through C56 for transmit Another important role of the VCO is that it is the stage that is modulated by microphone amplifier U4 which is discussed in Stage M Notice that the microphone amplifier output is coupled through C62 directly to the voltage control line for the varactor diodes Therefore any voltage variation imposed on that line will vary the VCO frequency in step with that variation If the frequency is varied in step with speech patterns or other audio signals such as tone shifts we are generating frequency modulation hence FM D5 and R31 perform an interesting function Remember that the VCO control voltage has a range of about 1 0 volts DC low frequency to 7 0 volts high frequency Therefore more modulation voltage is needed at higher VCO frequencies As the VCO control voltage increases D5 turns on and places R31 in parallel with R33 reducing the resistance in the line to half and thereby increasing available modulation voltage Finally it should make sense that the VCO should have a very pure source of well filtered DC completely free of AC hum alternator whine or other disturbance R19 and 47 uf C40 form a basic low pass filter Transistor Q4 serves as an electronic capacitance multiplier The actual effect of the filter is that the beta of Q4 multiplies the 47 uf to the equivalent of installing a huge 4000 5000 uf capacitor in the VCO area FX 50 82 KIT ASSEMBLY PHASE 1 Stage A DC Power Regula
41. 00 ohms brown black brown F4 Install C43 22 pf marked 22 F5 Install R22 47K yellow violet orange F6 Install C51 56 pf marked 56 F7 Install Q7 NPN type 2N3904 Be sure to select the correct transistor type and to orient the flat side as pictured F8 Install C45 01 uf disc capacitor F9 Install R30 51 ohms green brown black F10 Install C54 100 pf marked 100 F11 Install L7 another blue color 5 5 turn plastic molded adjustable coil F12 Install L6 the pre wound 11 turn 228 diameter coil It has more turns than the other two pre wound coils in your kit FX 50 84 A Radio Shack or local electronic parts distributor Resistors electrolytic capacitors disc capacitors common NPN or PNP transistors Zener diodes switching diodes voltage regulator 5V hookup wire LED controls antenna connector replacement 1 amp fuses B Order from RAMSEY ELECTRONICS Most RF and VHF transistors coils crystals PIN diodes varactor diodes trimmers filters and most IC chips C U1 and U6 are Motorola devices These parts might be in stock at service shops featuring Motorola equipment There are acceptable standard replacements for some of the semiconductors used in the transceiver SK and ECG standard replacements are stocked by local electronics parts distributors or may be ordered through a Radio Shack store The following chart should help you make the most cost effective choice if replaceme
42. 1 or 104 G35 Install diode D8 type 1N914 or 1N4148 Orient the banded cathode end correctly N A Ra I Be Be RR RS B S R FX 50 95 make mistakes skipping connections causing solder bridges etc Some builders may prefer to push ahead and do all of the repetitive soldering as a single operation while others do better work with frequent breaks in the phases that involve repetition of steps The suggested order of assembly is for the benefit of the latter group If you wish to proceed differently feel free to do so Just be sure to check off the respective assembly steps as you finish or review your work g R Be RoR R R R Gia Insert the 28 pin DIP socket for U6 into its PC board position and slightly bend the 4 outermost pins to hold it in place G1b Examine the solder side and verify that ALL 28 pins are extended into their respective holes Press the socket squarely onto the board solder the 4 corner pins check for proper seating then solder remaining pins G2 Install U6 MC145152 check that all pins are fully seated G3 Install oscillator crystal Y2 10 240 MHz Be sure it is firmly seated on the board then solder G4 Install C87 39 pf G5 Install C80 15 pf G6 Install R38 10K brown black orange G7 Identify C81 a 35 pf trimmer capacitor C81 has a black body and orange top Press it in place flat on the PC board G8 Solder C81 s two connections GQ Identify and install U5 the
43. 1024 512 256 128 64 32 16 8 0 1 0 0 0 0 1 0 1 1 1 Binary code for N 4 280 Now invert all the bits 1 0 1 1 1 1 0 1 0 0 0 Add 1 1 0 1 1 1 1 0 1 0 0 1 You ll see this is the number programmed into the Receive offset matrix line for a minus 21 4 MHz offset EXAMPLE 3 TWO S COMPLEMENT WITH CARRY For illustration purposes we ll pick an odd ball offset such as 640 KHz In this case N 640 5 KHz 128 8192 4096 2048 1024 512 256 128 64 32 16 0 0 0 0 0 0 1 0 0 FX 50 36 Stage H Frequency Programming Understanding and Building your Diode Matrix 2000060 ON 24 soan 3 gt gogagee x N RRR RIGS FX 50 97 wD vads za o Ag 0 AZL 0 za z N ED so gt o OY Brag zza C on Balu o YMd 6 G86 Similarly install diode D10 same type as D8 G87 Similarly install diode D24 FX 50 96 Invert all bits Add 1 Sum at 8 bit position carry 1 Sum at 16 bit position carry 1 Sum at 32 bit position carry 1 Sum at 64 bit position carry 1 Sum at 128 no carry needed Final result Binary code for N 128 BASICS OF EXTERNALLY CONTROLLED FX TRANSCEIVER FREQUENCY SWITCHING The 12 front panel switched channels with never a need for a crystal will cover most applications generously Yet many of us will want to figure out ways for easy frequency programming of still more channels especially if we do a lot of cross country travel Rathe
44. 6 METER AMATEUR PLL SYNTHESIZED FM TRANSCEIVER 50 55 MHz IMPORTANT NOTICE This manual must be printed in separate booklets in the sections shown below NEVER print this manual as a single book 1 12 121 132 Published in Three Sections FX 50 132 A DEDICATION The Ramsey FXseries FM Transceiver Kits are writing a truly NEW chapter in the annals of the ham radio story Growing numbers of today s radio amateurs ARE willing to build understand adjust and maintain modern VHF gear capable of digital frequency programming and data communication as well as FM voice How do we know We know it because during 1991 thousands of hams worldwide built and are using our pioneering FTR 146 for two meters The FX Transceiver design was developed in immediate response to those builders suggestions wish lists and inquiries This publication is dedicated with deep thanks to all those FTR 146 builders FX 50 VHF FM Transceiver Reference and Kit Assembly Manual Ramsey Publication No M50FX First Printing December 1991 Copyright 1991 1994 by Ramsey Electronics Inc All Rights Reserved Revision number 2 0 Published by Ramsey Electronics Inc Printed in the United States of America RAMSEY ELECTRONICS INC Amateur Radio and Hobby Kits Dept 793 Canning Parkway Victor New York 14564 716 924 4560 Fax 924 4555 FX 50 2 FX50 131 Improper output power measurement TABLE OF CONTENTS l ae The Ramsey FX 50 Transceiver
45. A in the PLL synthesizer circuit There must be a 21 4 MHz difference between the receive and transmit frequencies of the VCO This swing cannot be accomplished by PLL programming alone The VCO must be able to stay in range with the synthesizer PIN diode D1 shunts the additional series inductor L6 when in transmit mode by the action of transistor switch Q5 In receive mode D1 is turned off allowing L6 s inductance to be added in series with the VCO tunable coil L7 This additional inductance allows the VCO to tune lower in frequency The VCO output is fed into U3 MC12017P a dual modulus A64 65 prescaler the output of which is fed to the A and N counters in U6 The output is also routed through C35 for receive and Q10 through C56 for transmit The VCO is is frequency modulated by microphone amplifier U4 D5 and R31 perform an interesting function Remember that the VCO control voltage has a range of about 1 0 volts DC low frequency to 7 0 volts high frequency Therefore more modulation voltage is needed at the higher frequencies As the VCO control voltage increases D5 turns on and places R31 in parallel with R33 reducing the resistance in the line to half and thereby increasing available modulation voltage FX 50 22 R70 limits the current drawn by D17 to a safe level This LED usefully assures that the otherwise silent PTT circuitry is indeed functioning and obviously has nothing to do with the RF output of the transmit
46. AN AUXILIARY OFFSET 1 Install NO diode in SIMP RPT or RPT for the channel that gets a non standard offset 2 Program the AUX matrix row for the desired offset following our published instructions 3 Connect the channel row to the AUX matrix row by installing a diode as shown below The cathode end is soldered to the diode programming bridge In this example Channel 3 uses the auxiliary offset 2 29 BO 9 R 9 DIODE JUMPER FOR CHANNEL 3 o lt PER MARKINGS ON PC BOARD F SIMP RPT RPT 32K 16K E E E E i FX 50 34 N for 52 525 MHz 52525 5 10 505 Remainders and NO YES Position doodles Can you subtract 32768 a ty a 32K Can you subtract 16384 an ce 16K Can you subtract 8192 ooa fo Jel x Can you subtract 4096 Po e o K o Can you subtract 2048 265 Can you subtract 1024 re a ae Can you subtract 512 ee 2 512 Can you subtract 256 a ae ae 256 Can you subtract 128 ae Fa 128 Can you subtract 64 Subtracting from N Can you subtract 32 Can you subtract 16 Can you subtract 8 Can you subtract 4 Can you subtract 2 Can you subtract 1 Now install Programming Diodes at all YES positions and we re done The practical result from the preceding exercise is that we install diodes only in the YES positions on the matrix Compare these results with the diode programming illustrated for 52 525 MHz Simplex on the schematic diagram If you do not yet understand EXACTLY what we di
47. AND Q2 RECEIVE PASS RECEIVE PRE AMP FILTER PRE AMP 21 4 MHz FILTER AMPLIFIER SECOND PLL CONTROLLED VCO PROGRAMMED 21 4 MHz LOWER THAN DESIRED RECEIVE SIGNAL Q6 RECEIVER MUTING gt SPEAKER FX50 75 CR30 Prepare three 8 lengths of hookup wire for connecting R13 the 10K Squelch Control Strip back 14 from one end of each wire Tin all ends CR31 Install C11 01 uf disc capacitor marked 01 or 103 CR82 Install D23 6 2 volt zener diode gray body black band Observe correct placement of the banded cathode end Zener diodes are widely used as voltage regulators They have the interesting property of keeping a constant voltage across their terminal leads CR33 Install C35 100 pf marked 100 101 or 101k The last 4 steps involved the building of a voltage regulator to supply a steady source of voltage to the receiver IC chip At this point in your work you could actually receive strong local signals by connecting an antenna wire at C78 and a high frequency signal source e g a signal generator to the input of U1 The signal you would receive would be on a frequency of the signal generator frequency plus 21 4 MHz Because we have not yet constructed any of the input circuitry Stage DR you would also hear any signal on the signal generator frequency minus 21 4 MHz PRECAUTION ON WIRING FOR CONTROLS JACKS ETC The volume control squelch control speaker jack and power cord a
48. CLASS license or higher is required for operation in the Amateur 6 Meter band 50 to 54 MHz Proper licensing is required for MARS or CAP operations Amateur licensees are required by the FCC to maintain strict control over their equipment to prevent unlicensed operation either in the amateur band or outside it FCC regulations ENFORCE severe penalties for unlicensed operation of radio transmitting equipment and for interference with other communications services whether malicious or accidental Ramsey Electronics Inc sells the FX 50 transceiver solely for correctly licensed operation It is the sole responsibility of builders and operators of this RF electronics device capable of emissions controlled by FCC Rules to understand and comply with those rules FX 50 4 Some channels are off frequency by different amounts Refer to preliminary check 5 Common faults Improper diode programming Solder shorts between traces There re a lot of traces between U6 and the diode matrix Transmit Section Faults manual pages 25 26 118 123 1 No power output Check for proper VCO frequency b Check 8T and 12V to the transmit Buffer Driver and Final stages c Ensure D7 is forward biased approx 7 2 VDC at junction of L17 amp R54 d Double check all components in transmit section for proper value and placement e Check for heat on Q9 and Q8 If they re warm chances are they re working C
49. DC During Receive D6 is on and permits RF to flow from the antenna through C47 to the amplifier stage just discussed Because any DC device needs a ground FX 50 21 connection as well as DC D6 is grounded through RF choke L17 which prevents the antenna RF from being shorted to ground During Transmit D7 passes RF from the transmitter to the antenna and L17 again prevents loss of RF to ground During transmit D6 is blocking transmitter RF from the receiver circuit For maximum protection of the more delicate receiver circuit D2 is turned on during transmit to ground any stray RF Stage E F The FX Transceiver VCO The VCO Voltage Controlled Oscillator provides basic frequency control for both transmit and receive modes It is essential to understand its function in the transceiver circuit Q7 is the oscillator transistor L7 D3 and D1 are key VCO components After the VCO is assembled on the PC board the interested builder is given the option of experimenting with it in receive mode before working on the PLL synthesizer This is done by applying a variable DC control voltage through a pot to TP1 Otherwise TP1 is available for checking VCO control voltage during initial alignment TP2 permits checking VCO frequency output with a frequency counter TP3 permits checking the output of the 12017 A64 65 dual modulus prescaler U3 The control voltage for D3 the varactor diode is supplied through R47 and R25 by the output of U5
50. FM squelch circuit to remain open after being broken by a weak signal which fluctuates further INPUT INVERTING see Op Amp INPUT NON INVERTING see Op Amp I O acronym meaning Input and Output port or connection JUMPER Short plain wire soldered to interconnect points in a circuit not otherwise connected by board traces or other wiring KEY to key to turn on a transmitter s carrier signal momentarily whether by a telegraphy code key the root of this very common radio jargon or by a push to talk switch L C A tuned circuit made of inductor L and capacitor C LIMITER The portion of an FM receiver circuit which chops off noise and AM amplitude modulation It processes the IF signal so that only FM will be detected LOCAL OSCILLATOR LO An oscillator in a superhet receiver whose output is mixed with another signal such as antenna input See SUPERHE T LOCK The condition in a phased locked loop PLL in which all sections are working together as intended and designed LOOP FILTER See PLL The output of a PLL phase detector is in the form of pulses The frequency of those pulses depends on the reference frequency The loop filter smoothes out these pulses into a clean DC control voltage for the VCO See VCO LOW A logic level at or near zero volts See HIGH MATRIX A methodical criss crossing of many connections MC Prefix for parts made by Motorola Inc MIXER A circuit section which g
51. K brown black red M38 Install the LED transmit indicator D17 Correctly identify the anode side lead which is the longer of the two Install the LED with full lead length extending above the board so that the LED can be positioned in the front panel hole M39 Prepare two 11 wires or 11 of 2 conductor wire by stripping back each end 1 8 and tinning with solder and solder one end of each to IN and GND MIC between C86 and U1 MICRDPHONE JACK LONG LEAD y IN GNO M40 Study microphone jack J4 and the above drawing Solder the other two wire ends to the jack lugs as shown STAGE M PROGRESS TEST 1 Remove the jumper wire between 8R and 8V 2 Check the PC board for wire scraps untrimmed leads etc 3 Connect an ICOM compatible speaker microphone to the Mic jack 4 Connect DC power antenna and speaker 5 Turn the power switch ON and verify that receiver still works properly 6 Select a steady signal or turn the squelch control so that the background noise is audible 7 Press the microphone button the TX LED should light and the receiver should be silenced 8 Touch a wire from ground to pin 3 of the Packet I O jack Do the same with any resistor that is 47K or lower Either way you should get the same results as in Step 6 9 Disconnect the DC Power OPTIONAL Interested builders might wish to verify microphone amplifier operation at PC board point PL before proceeding
52. Manual is organized into three sections General Reference Information Kit Assembly Phase 1 and Kit Assembly Phase 2 FX 50 GENERAL REFERENCE INFORMATION Notice Regarding FX 50 Frequency Coverage eeseeeesseeeeeeee 4 FX 50 Technical Specifications cc ceeeeeeeeeeeeeeeneeeeeeeaeeeeeeeaeeeees 5 Introduction to Transceiver Kit Assembly ceeeeeeeeeeteeeeeeeaeeeees 6 A Message to Ham Radio Beginners cceeeeeneeeeeeeneeeeeeeaeeeees 8 DC Power Supply Considerations ccccceeeeeeeneeeeeeeaeeeeeeeaeeeees 9 Enclosure and Hardware Considerations c ceceeeeeeeeeeeeeees 10 Ramsey CFX Transceiver Enclosure Kit eeen 12 Guide to PC board I O Connections 0 ceceeeeeeeeeeeeeneeeeeeeeeeeeeeee 14 Microphone amp Speaker Information cccceeeeeneeeeeeeaeeeeeeeaeeeees 16 A Few Antenna Considerations eeeeeeeeeeeeeeeeeeeeeeeeeeeeeeaaees 16 VHF Packet Data Operation 0 ccceceeeeeteeeeeeeeeeeeenaeeeeeeaaeeeeeeea 17 FXseries Transceiver Block Diagram cceccseeeeeeeneeeeeeeaeeeees 18 FX 50 Circuit OVErViOW ee ecceeeee eee eeeeeeeeaeeeeeeeaaeeeeeeaaeeeeeeaaeeees 19 Quick Reference Programming Guide eceeeesteeeeeeeneeeeeeee 28 FX 50 Programming Worksheet eecseeeeeeeeeeeeeeeaeeeeeeeaeeeees 30 Using Computer BASIC as a Programming Aid 0 eceeeeeees 31 How to Activate an Auxiliary non Stand
53. TT circuitry is supposed to accomplish Understanding our design clearly and assembling it correctly will save many headaches and will ensure reliable FX transceiver operation U4 is a quad op amp which means 4 operational amplifiers in one DIP package Two are used as a conventional microphone gain amplifier and the other two are used in the PTT push to talk circuit Capacitor C83 couples microphone audio to U4A and isolates the audio AC from the PTT circuitry DC Op amps are designed to run from both a positive and a negative voltage source U4 is powered by a single 8V supply through the use of a voltage divider network R59 R40 The gain of the amplifier is established by the ratio of R56 to R58 A passive low pass filter is formed by R51 and C89 The B section of U4 and its associated components form an active low pass audio filter The output of U4B is fed through C62 to modulate the VCO control voltage as explained in Stage E F Trimmer R46 permits adjustment of modulation level The purpose of Q11 is to shunt the microphone circuit straight to ground during receive so that it cannot possibly disturb the VCO An accessory modulation input is provided at PC board point PL for direct injection of DTMF or CTCSS tones etc The PTT circuit is designed to accommodate the popular ICOM compatible speaker mikes Notice that a single line at J4 serves both audio and PTT functions The one shielded wire into the microphone takes care
54. acitor marked 01 or 103 Os A Es Re SIR De B9 Install NPN transistor Q6 Be sure to have identified it correctly as one of the five 2N3904 transistors used in your kit Not one of the 2SC2498 RF transistors and be sure to orient the flat side as illustrated Before soldering press the transistor as far into its 3 holes as reasonably possible B10 Install R109 47K yellow violet orange Note that this is another of numerous vertical installations of resistors The body of such resistors should be snug against the board at the designated hole with the other wire neatly looped into the other hole without needless excess Ci na B11 Cut three 8 lengths of hookup wire or 8 of 3 conductor wire to connect the Volume Control to the three points designated on the PC board Strip and tin all six ends referring back Fx PcBoarD to Stage A instructions if necessary or helpful 6 ay Creu ai FUSE B12 Refer to the drawing and correctly v interconnect the BGROUND di Volume Control s three lugs to the 3 connecting FX 50 66 FX 50 67
55. adio Shack sells a variety of noise suppression capacitors and chokes The ultimate solution which has been tested is to run the transceiver from a smaller accessory battery If you plan to build a power supply for fixed station use there are numerous construction articles in ham and electronics hobby publications A convenient new book featuring easy to find components and clear explanations is Building Power Supplies Radio Shack 276 5025 FX50 9 ENCLOSURE amp HARDWARE CONSIDERATIONS The companion CFX case and knob kit is sold as a separate option ONLY as an accommodation to those radio hams who have their own ideas or resources for the finishing touches However a proper case for your FX series is much more than a finishing touch since the controls and jacks are panel mounted and proper RF shielding is required The CFX case measures 9 3 4 L X 6 W X 1 5 H 9 x 6 dimensions are minimum for accommodating the PC board The height may vary if you wish to include an internal speaker accessory PC boards additional front panel controls or indicators etc If you are new at all this and do not already own a suitable enclosure plus that collection of hardware and knobs that every ham seems to accumulate here is what you need to know if you are hesitant to purchase the CFX case kit A Blank electronics enclosures have become among the most expensive hardware in the industry especially if you are buying just one unit This
56. aracteristics although at a cost typically 20 to 25 We leave this option open to you The RF present now strongly favors signals that are in the desired frequency range of interest This RF is amplified again by Q2 and then applied to U1 the main receiver IC chip The RF from the antenna input to U1 now can be said to be restricted to the desired tuning range of the transceiver Unwanted signals have been doubly rejected and the desirable signals have been doubly amplified Take a look at PIN diodes D2 D6 and D7 These tiny diodes are amazing devices which have made relays and so forth all but obsolete for T R switching purposes To put it simply a PIN diode can pass RF energy either way when it is turned on by DC voltage and also block RF from the other direction when it is not powered by DC Just picture RF passing with the anode arrow and picture the cathode band as a barrier The symbols 8R and 8T mean that voltage is present at such a point during Receive or Transmit only not both at the same time During Receive D6 is on and permits RF to flow from the antenna through C47 to the filter and amplifier stages just discussed Because any DC device needs a ground connection as well as DC D6 is grounded through RF choke L17 which prevents the antenna RF from being shorted to ground During Transmit D7 passes RF from the transmitter to the antenna and L17 again prevents loss of RF to ground During transmit D6 is block
57. ard Offset ee 34 Programming Minus Offsets cceceeeeeseeeeeeeneeeeeeeaeeeeeeeaaeeees 35 Basics of Externally Controlled Frequency Switching 37 FXseries GLOSSARY of Terms 0 ceeeeeeseeeeeeeeeeeeeeeaeeeeeeeaeeeees 39 Troubleshooting Guide s riii pimi iarria in EN A ER A 46 Note on Replacement Parts cccceeeeeeeneeeeeeeaeeeeeeeaeeeeeeeaaeeees 48 RAMSEY ELECTRONICS FX Kit Warranty Terms 50 FX 50 Master Component Index ceceeeeeeeeeeeaeeeeeeeaeeeeeeeaaeeees 52 PC Board Assembly Information 0 c eccseeeeeeeeeeeeeeeaeeeeeeeaaeeees 56 KIT ASSEMBLY PHASE 1 Assembly and Explanation of Circuit Stages A through F including Kit Parts List kit building tips and preliminary receiver amp VCO KIT ASSEMBLY PHASE 2 Assembly and Explanation of Circuit Stages G through TX includes all Frequency Programming directions plus alignment and transmitter tuneup a fal a gai uaddtewndse E ola paced angitaedseeGh adsl sai Ee 87 124 FX 50 130 FX50 3 IMPORTANT NOTICE The Ramsey FX 50 VHF FM Transceiver is capable of TRANSMITTING as well as receiving on any frequency in the range of 50 to 60 MHz making it suitable for a wide range of VHF communications requirements Operation of the Transmit function of this equipment requires an appropriate license issued by the Federal Communications Commission FCC for the class of operation intended The FCC issued TECHNICIAN
58. breaks the squelch SUPERHET A receiver design that converts the incoming desired frequency to a lower Intermediate Frequency IF where most of the gain and bandpass characteristics reside TOROID A style of making coils or inductors where the insulated wire is threaded wound around a metallic form shaped like a doughnut This style of coil making generally eliminates any need for additional shielding which may be needed to make the coil s inductance immune to the presence of other nearby components or objects with metallic content TRIMMER either a capacitor or resistor miniature and variable intended to permit exact final adjustment of circuit values TX Abbreviation for transmit transmitter transmitting T R Abbreviation for Transmit Receive Switching which can be accomplished by manual switches relays or solid state devices such as the PIN diodes used in the FX transceivers FX 50 43 UNLOCK unlocked refers to the condition in a PLL phased locked loop where one or more elements of the loop become defective or incorrect preventing the phase detector from supplying the correct control voltage to the oscillator for the intended frequency of operation VARACTOR a diode whose capacitance can be varied in step by the amount of DC voltage applied to it The higher the voltage the lower the capacitance See also VCO VCO Voltage Controlled Oscillator an oscillator whose frequency is varied by DC vo
59. ceived the MINIMUM repair fee of 49 00 or authorization to charge it to your credit card account INCLUDE a description of the problem and legible return address Do not send a separate letter include all correspondence with the unit Please do not include your own hardware such as non Ramsey cabinets knobs cables external battery packs and the like Ramsey Electronics reserves the right to refuse to repair ANY item in which we find excessive problems or damage due to construction methods To assist customers in such situations Ramsey Electronics Inc reserves the right to solve their needs on a case by case basis without creating policy or precedent Please understand that our technicians are not volunteers and that set up testing diagnosis repair and paper work can easily take over two hours of paid employee time on even a simple problem Understand too that alignment is part of the kit building process and is not covered by this Warranty Of course it we find that a part was defective in original manufacture there will be no charge to repair your kit But please realize that our technicians know the difference between a defective part and parts burned out or damaged through improper use or assembly 4 REFUNDS You are given ten 10 days to examine our products If you are not satisfied you may return your unassembled kit with all parts and instructions and proof of purchase to the factory for a full refund The returned package sho
60. d in this exercise and why we suggest in the strongest possible terms that you work at getting it clear before doing any further work on your transceiver FX 50 99 Stage H FREQUENCY PROGRAMMING Understanding and Building the Diode Matrix The labeling of the 16 parallel programming inputs of U6 should have a familiar ring to anyone with at least some understanding of computer principles which should include all of us by now Even though our desired N number is a five digit decimal number it is programmed as a 16 bit BINARY number Binary numbers can be as big as you like but we get there by counting ona base of two either 1 or 0 yes or no on or off This is of course the foundation for all digital circuitry The programming inputs of your FX transceiver synthesizer can be set for any frequency in its range using the correct N number by means of the diode programming provided with your kit or with simple switches or by digital switching circuitry or by a dedicated microprocessor circuit or by a control circuit controlled by the same computer you use for packet etc We will cover only the diode programming approach with some brief suggestions on externally controlled switching It is very intentional on our part to leave innovative programming schemes up to FX transceiver users because there s no single best way to do it for everybody Our job was to break the price barrier on a practical state of the art VHF transc
61. d inductor resembling a resistor but larger with 2 red bands on its body DR7 Install R21 470 ohms yellow violet brown DR8 Install R119 100 ohm brown black brown DRg Install R16 10K ohms brown black yellow DR10 Install D2 BA482 PIN diode marked BA482 Be sure to orient the cathode band properly A A RA R R DR11 Install C53 01 uf disc capacitor marked 01 or 103 DR12 Install C25 01 uf marked 01 or 103 R DR13 Install Q3 2SC2498 transistor observe correct placement of the flat side DR14 Install R17 270 ohm red violet brown LN DR15 Install R12 51 ohms green brown black DR16 Install C17 22 pf marked 22 FX 50 78 10K squelch control potentiometer R13 12 position rotary switch S2 3 5 mm jack miniature J2 speaker 2 5 mm jack subminiature J4 microphone 5 pin female DIN PC mount connector J1 packet SO 239 coaxial RF connector J3 28 pin DIP IC socket for U6 DC power cord with inline fuseholder and 1A fuse 1 2 panel mount strain relief for DC power cord length of No 20 bus wire to make diode matrix bridges length of No 24 bus wire to make L9 and L19 hookup wire as needed may include 1 2 or 3 conductors wire cable ties 5 16 x 18 bolt to wind coils on for perfect spacing document packet including this manual RRRARRRRRRRRRARKRA _ S O Ss SB SS oS SH tt REQUIRED NOT SUPPLIED WITH KIT Thin diameter rosin
62. ding Identify and install the following components TX8 R34 100 ohms brown black brown TX4 C56 001 uf marked 001 or 102 TX5 R36 15 ohms brown green black TX6 C84 01 uf marked 01 or 103 TX7 Q10 NE021 small black disc stuck to paper marked 021 The longest of the three leads is the collector which points towards C76 Remove Q10 from its paper backing bend the leads down and install it as shown It should sit snug against the PC board TX8 R110 10K brown black orange TX9 C97 01 uf marked 01 or 103 TX10 C44 01 uf TX11 L11 2 2 uh choke green body with red and gold color bands TX12 C76 100 pf marked 100 or 101 TX13 R28 51 ohms green brown black A A RA R TX14 Trimmer capacitor C75 TX15 C66 001 uf ROR RO ORL R FX 50 118 1 PRIMARY CONNECTIONS PWR near L20 12 15 volts DC from S1 GROUND DC from battery or power supply SPEAKER both connections near U6 and U2 MIKE both connections IN amp GND near notched end of U1 SQUELCH three connections near L1 VOLUME three connections near VR1 and C42 ANTENNA Center of SO 239 connected at RF OUT near C27 CHANNEL SWITCH Row of holes numbered 1 through 12 The switch wiper moving contact is wired to 5V near 1 EXT AUDIO must be jumpered per options to enable pin 4 of J1 2 TEST POINTS 12V 8V 8R 8T permit checking for presence of those voltages 8R Receive mode 8T
63. double check the accuracy of your parts installations However experienced builders will recognize that VHF signals could now be received very well by connecting an antenna and tuning a signal generator coupled to pin 2 of U1 provided that the T R circuitry is operational A more useful preliminary receiver test will be conducted after we complete the VCO stage FX50 79 STAGE DR ASSEMBLY In keeping with our learn as you build kit building philosophy we will install only the components needed for receiving Be very attentive to capacitor values in picofarads and to coil descriptions throughout this section DRI Install C26 100 pf marked 100 or 101 DRz2 Install L17 2 2 uH in upright position with the inductor s body in the designated hole This is a molded inductor resembling a resistor but is larger Look for 2 red bands on its body DR8 Because it must dissipate slightly more power resistor R54 is larger than most of the resistors used in this circuit Its value may be 200 or 220 ohms red black brown or red red brown Install R54 in upright style DRA Install C47 01 uf marked 01 or 103 DR5 Correctly identify and install PIN diode D6 It is the only BA479 used in the circuit and its number is stamped on the diode body Be sure to orient the cathode end correctly DR6 Install L22 another 2 2 uH in upright position with the inductor s body in the designated hole This is a molde
64. e all parts values are correct and that D9 is oriented correctly FX 50 64 STAGE CR FM RECEIVER CIRCUIT DUAL CONVERSION SUPERHET WITH IF FILTERS 3T Oo Ont a z AWN 96 1 Q es x4 SOINOMIOIT9 AISWWe Qa000404 Ma RAN basen tert cpp eecaosece QRBAR AxIgee 3 Fos RB CED nt LO OG a T RIS ge gt O ai o 4 _ fli a G13 oist TErau R be y D a z of cal FX 50 69 points on the PC board SPEAKER JACK GND OU Stage B Receiver Audio Amplifier The secret to the fine performance of the LM380 audio amplifier lies in careful selection and physical positioning of the several external components required to complete its circuit The LM380 is a self contained general purpose audio amplifier capable of over 2 watts audio output with a voltage gain of 50 Audio from the FM discriminator U1 is fed through C7 through the 10K volume control R7 to pin 2 the amplifier input The amplified output at pin 8 is available through C34 to both the speaker jack and pin 4 of the Packet I O Jack Capacitor C41 in series with R108 across this amplified output are recommended good practice to prevent self oscillation of the amplifier IC Pin 1 is bypassed to ground through C48 in normal operation If pin 1 is grounded directly the internal bias of the LM380 is upset and the amplifier is silenced We are able to put this characteristic to practical use using Q6 as a simple s
65. e developed in C85 g2 g 1 uf would slow down the PLL during major frequency swings such as just os go going from transmit to receive D8 and D10 are set up back to back across g3 go voltage dropping R48 Whenever there is a major frequency shift which 128 eQ means a significant VCO control voltage change one way or the other one 2612 a diode or the other is switched on to short out R48 and one r discharge C85 This lets the 52525 KHz PLL relock instantly C85 on s recharges and the diodes 5 KHz become no factor in the etek 2 circuit 1K a e 4K Sk RTIII AVIS Stage H The Diode Matrix and PLL Synthesizer Programming There are two diode matrix programming areas on the PC board The obviously larger area is for frequency channel programming The second space is for offset programming added in by U7 U10 a o gi Q a N The 19 100K resistors at the frequency programming matrix and the 14 100K resistors at the offset matrix are pulldown resistors to ensure positive logic switching action of U6 CEDOS 673 Q15 and its associated switching diodes ensure that the desired offset is switched in during transmit that offset programming does not interfere when simplex is desired and that the offsets do not interfere with receiver operation and that receiver programming 21 4 MHz lower does not interfere with transmit operation N 0 AZI O RTF oS wads zza CO oo Baly lt D 5 Z aon A var
66. e or very tiny frequency offsets The 1 to 8K range provides plenty of flexibility for non standard channel spacing U7 through U10 are called 4 bit binary adders because they each can handle four binary addition operations For each bit there are A and B inputs and one S sum output Examine the schematic diagram closely and you will see that all the frequency programming lines are connected to A inputs and all offset lines go to B inputs Notice further that the binary positions of both matrixes correspond to each other exactly the 8K offset position goes to B1 of U7 and the 8K frequency programming position goes to A1 Their sum appears at S1 pin 1 and goes to U6 And so forth for all the other binary positions of both matrix areas We made it very easy for you to set up the required receiver frequency and standard 1 0 MHz transmit offsets Simply insert diodes correctly in the holes marked by circles solder and you re in business Here s a reproduced image of the PC Board s matrix area The silkscreen on the PC board may differ from the diagram below If so use the diagram and not the PC board silkscreen See how the standard offset positions are outlined with circles bb bbb bbb dd bb be REGY Or Ow O C60 OR On 0 on Ono On0 Oe RPT S O O a ce a RPT a S a AUX However it s worthwhile to understand why the diodes are in those positions Let s work backwards starting with the actual diode positions and discover why
67. e red R6 19 10K ohms brown black orange R5 16 24 27 38 47 48 49 50 55 60 62 67 90 102 104 106 107 110 4 22K ohms red red orange R43 44 52 53 12 47K ohms yellow violet orange R11 14 22 25 31 33 39 51 56 66 103 109 1 68K ohms blue gray orange R4 38 100K ohms brown black yellow R26 35 37 40 59 71 89 91 101 116 117 118 1 470K ohms yellow violet yellow R1 CONTROLS HARDWARE AND MISC 1 volume control potentiometer with switch may be any value from 10K to 100K R7 S1 RR BOR ROR RB ORR RB NVW woos RR FX 50 54 DR17 Install C22 27 pf marked 27 DR18 Install C49 8 2 pf DR19 Install C52 27 pf marked 27 DR20 Install C31 22 pf DR21 Install C18 01 pf marked 01 or 103 DR22 Install R10 100 ohm brown black brown DR23 Install R14 47K ohm yellow violet orange A A RA iy BE Be DR24 Install Q2 25C2498 transistor Observe correct placement of the flat side DR25 Install C79 01 uf INTERMISSION Notice how our work is methodically creeping toward all the FM IC circuitry you did in Stage CR DR26 Install C78 01 uf DR27 Locate one of the three blue colored molded plastic adjustable coils Install one in the L4 location DR28 Install another blue plastic coil in the L5 location Coils L2 and L3 will be installed later when we wind all the coils at one time Stage DR Progress Note No other testing is required at this point other than to
68. early recognizable and often will have a rectangular rather than disc shape Their markings may be 1 or 104 Small picofarad values are clearly stamped on capacitor bodies 100 pf units may be marked 100 or 101 We tried to make it clear in both lists and assembly steps that some components can have a RANGE of acceptable values even though a single value is indicated on the schematic the control document for this project A rule of thumb is that a value within 10 of the stated value will be fine 2 or 2 2 pf 4 7 or 5 pf 200 or 220 ohm and so forth 10 uf electrolytics may be 4 7 to 10 uf Remember that there s a reason for the tolerance codes for all parts Unless we scream in bold print that something must be exact down to the last micro henry ohm or partial picofarad PLEASE assume the 10 rule in sorting through your kit parts Manufacturer stamping patterns can vary and we sometimes need to use simple logic and deduction to identify parts particularly the extremely common ones For example if your kit includes 3 identical transistors with no apparent body marking at all you may presume them to be the 3 PNP transistors described as 2N3906 228256 or equivalent Check your manual or kit package for any insert page advising that a part identification or physical description has changed We cannot control how manufacturers may vary their product codes or colors of plastic Observe correct POLARITY when installing all diodes and el
69. easy as possible All these points are plainly marked on the board itself and highlighted on the facing page with a few other components for o onst a to Nae 3 EEE a o z AY 96 1 O ec x4 SOINOHLOITS AISNAVY ogogovoooooo BIKSeen o 32 J a 6 12 Q 25 o 3 Q 1K 9 2K e 4k Q Bk TITTI FX 50 14 TX16 C82 27 pf marked 27 or 27K TX17 C61 01 uf R TX18 Locate and install L12 the 2 1 2 turn coil wound previously in step TC1 Install it so it sits about 1 16 above the PC board TX19 Locate and install L14 the other 2 1 2 turn coil wound in step TC1 Install it so it sits about 1 16 above the PC board TX20 C103 150 pf marked 150 or 151 TX21 a Prepare the following tools for installing SMT chip capacitor C72 Tweezers Magnifier if needed Low wattage clean soldering tip b Unpack and study the design of the chip noting both ends are metallic c With an exacto knife or other blade carefully scrape off the green solder mask BACKOFPC from the back of the PC board where C72 op BOARD will be soldered Lightly pre tin both PC af p board points 4 o d Holding C72 in place across the two n io tinned points with tweezers gently touch one junction with the soldering tip The y c connection should solder easily c72 e Solder the other end and touch up the first one if necessary TX22 R29 51 ohms green brown black
70. ectrolytic capacitors Install all parts as close to the circuit board as possible unless otherwise noted Please review No 1 above FX 50 57 22 Use the extra spaces provided throughout this manual to write down the details of any changes or revisions noted on additional sheets that may be supplied with your kit 23 You will be installing various wires for switches controls and jacks very early in the assembly procedure This is contrary to normal building or manufacturing practice but will permit progressive testing of completed stages Follow the suggestion at the end of Stage CR for tying down these wires for protection and your convenience during further assembly work 24 Examine your FX circuit board Notice that the side with silk screened part outlines is covered almost completely with groundplane copper beneath the green solder mask This side is the Top or COMPONENT SIDE of the board All parts except SMT C75 will be mounted on this side The other side has most of the printed circuit traces and is called the Bottom or CIRCUIT SIDE ABOUT THE WIRE SUPPLIED WITH YOUR KIT Your kit parts include lengths of wire for making all needed connections from the PC board to the controls and jacks Because there is nothing critical in the functions of these wires the color and style of wire lengths actually packed in your kit may vary You may receive lengths of 2 or 3 conductor wire such as speaker cable or ribbon cable or a
71. eiver and make it highly useful for most operating patterns You have easy front panel selection of ANY 12 frequency pairs and never need to buy a crystal Nor should you ever need factory service THAT is what this transceiver is all about There are several methods for quickly finding the required binary code for a particular frequency and its N number 1 Descending Subtraction see Programming Worksheet 2 Printed reference lists see Popular 6 Meter Band Pairs 3 Computer programs see our sample BASIC program We recommend strongly that you fully understand how to make the attempted descending subtraction calculation yourself because that is your ONLY means for checking the accuracy of printed information computer programs or the operation of experimental programming circuits Let s walk through the programming of 52 525 MHz which is the national Simplex Calling Frequency and is also the demonstration and alignment standard for the FX 50 model You ll see exactly what we mean by descending attempted subtraction Also this is how the model BASIC program for diode programming included in this book is structured FX 50 98 4 You can connect as many of the channel rows as you wish in this manner but remember that each would follow the same non standard split you have programmed Only one such split can be programmed in the AUX matrix row It may be changed as needed If more than one non standard split is needed you can
72. emainders amp Doodles NO YES Position Can you subtract 32768 Pf 82768 Can you subtract 16384 PP 18884 R Can you subtract 256 a a 256 Can you subtract 128 a ae ce 128 Can you subtract 64 Can you subtract 32 Can you subtract 16 Can you subtract 8 Can you subtract 4 Can you subtract 2 Can you subtract 1 Will this be a Simplex chan SIMP nel Will Transmit be 1 0 MHz RPT LOWER than Receive HIGHER than Receive Install diodes in YES positions only If an auxiliary split is needed or if you are not licensed to transmit in a band portion do not install diodes in SIMP RPT or RPT positions FX 50 30 Easy enough Whenever you want a transmit offset that is higher than the receiver or repeater output frequency simply find the N number for the offset and program it on the offset matrix Here s one more example Let s say we want a 1 5 MHz offset 1 5 MHz 1500 KHz 1500 5 300 N Converting to binary Obviously 300 is less than all values from 8K through 512 meaning that we need no diodes in those positions Can we subtract 256 from 300 YES Therefore diode at 256 300 256 44 Can we subtract 128 from 44 NO Therefore NO diode at 128 Can we subtract 64 from 44 NO Therefore NO diode at 64 Can we subtract 32 from 44 YES Therefore diode at 32 44 32 12 Can we subtract 16 from 12 NO Therefore NO diode at 16 Can we subtract 8 from 12 YES Therefore diode at 8 12 8 4 Can we
73. en if you are following your own assembly sequence This procedure will prevent damage to Q9 and Q8 during the initial test and alignment procedure 3 Do not attempt to re engineer our transistor orientation illustrations Simply point flat sides or tabs as illustrated 4 After installing all parts you will see a few empty holes in the circuit traces on the top or component side of the board These plated through holes are placed intentionally to connect with traces on the solder side The hole IS the connection However if these holes nag at you simply fill them in with a touch of solder AFTER verifying that all parts have been placed and installed correctly 5 Additional empty holes are marked on the PC board to allow for easy connection of accessories or modifications as you begin to customize your transceiver See GUIDE TO FX CIRCUIT ACCESS POINTS 6 The purpose of check boxes e in the assembly steps is to make it easy to check the accuracy of your work at the end of each step 7 Almost all resistors are mounted in a vertical upright position You can see that the wire leads for resistors come in several styles If a resistor s pre trimmed lead is ever too short for upright installation simply solder a scrap wire nipped from another resistor to extend its length 8 Some of the resistors and miniature inductors used in this project require upright or vertical installation It is important to follow the orientation
74. ent test point If you do not wish to conduct this test simply double check the accuracy of your work in this stage and proceed to the Frequency Synthesizer section FX 50 86 52 525 MHz Simplex before you pursue troubleshooting It is very important to have a clear understanding of how to program the frequency synthesizer and offset matrixes of your transceiver FX 50 47 NOTE ON REPLACEMENT PARTS If you lose or damage parts during assembly or testing you may of course order any needed replacement parts by writing or faxing the Ramsey Electronics Inc factory Some of the more common parts may also be picked up at Radio Shack or other local parts distributors Use EXACT values when replacing parts Following is a GENERAL guide to obtaining parts for your transceiver as quickly as possible Part ID Type Recommended source RE Ramsey RS Radio Shack Q1 etc 2N3904 RS 276 1617 Q12 13 14 PNP 228256 RS276 1604 or 2N3906 Signal diodes 1N4148 1N914 RS276 1620 pack of 50 D3 BB505 RE D1 D2 D7 BA482 ECG553 or RE D6 BA479 RE D18 1N4002 RS276 1102 1N4003 Part ID Type Recommended source RE Ramsey RS Radio Shack FX 50 48 F13 TEMPORARY RECEIVER PTT T R CONNECTION OMIT this step if you prefer to install ALL transceiver parts before any testing or use of the Receiver alone If you wish to conduct further tests or put the receiver to work it is necessary to solder a 5 length of hookup wire from the ho
75. equire extra written detail You ve just been through a lot of that in this stage The following steps are more typical of how many upcoming installation FX50 63 directions will be given A183 Install C2 001 uf disc capacitor It may be marked 001 or 1 nf or 102 102 means a one a zero and two zeros which equals 1000 pf 1000 pf is the same as 001 uf This notation 102 is similar to the resistor color code to indicate resistance values A14 Install C3 001 uf A15 Install C4 001 uf A16 Install C1 001 uf A17 Install C65 1 uf It may be marked 1 or 104 As above 104 means a one a zero and four zeros 100 000 pf which is the same as 1 uf On the schematic C65 is located near J4 and U4 and couples packet audio to the microphone input line R A R R A18 Select D9 one of the many 1N914 or 1N4148 switching diodes used in the circuit Don t confuse these diodes with the smaller PIN and varactor diodes used in later stages Notice the dark band at one end designating the cathode and notice how the cathode end is imprinted right on the PC board A19 Install D9 A20 Install R42 2 2K red red red This is an upright installation like D18 previously installed Almost all resistors will be installed this way Like C65 R42 and D9 are shown near J4 on the schematic and complete the External PTT connection between U4 and J1 No testing of the Packet components is required but make sur
76. er riding all background noise or hiss on FM receivers FX50 39 CCW see CW below COR Carrier Operated Relay a switching circuit activated by the detection of a carrier signal in a receiving circuit CW TWO common meanings in electronics Continuous Wave for the communicating of Morse code signals or Clockwise to designate a point on a variable control CCW therefore means counterclockwise DECIMAL in computer or programming context decimal refers to counting by tens our traditional way in contrast to your computer s binary counting by 1 s and O s or the hexadecimal system counting by 16 s See N and BINARY DIP Dual Inline Package referring to IC s and their sockets or any other component DIP Switch etc The line refers to rows of PC board or perfboard holes that are 0 1 apart Dual means two rows Therefore SIP would mean a SINGLE row device DISCRIMINATOR FM terminology for detector See FM DUAL MODULUS as in dual modulus prescaler or divider a circuit which divides a frequency by two different ratios depending on pin selection for example 64 or 65 See PRE SCALE FILTER ACTIVE FILTER CERAMIC FILTER CRYSTAL FILTER HI PASS Filters are used in DC Audio and RF circuits Understanding them is essential FILTER LOW PASS electronics know how The Radio Amateurs FILTER BANDPASS Handbook covers the subject of filters very FILTER PASSIVE well FM Frequency
77. est catch on to new ideas and concepts The VCO integral to the PLL was discussed and tested in the preceding assembly stage What we have so far is a master oscillator for the transceiver that can be tuned by varying the voltage applied to the varactor diodes All we really need now is a super reliable way of controlling the voltage applied to those varactor diodes so that we can put that oscillator on any VHF channel we want with 5 KHz precision And this control obviously must be extremely stable since a change of only a few picofarads can tune through many MHz of VHF spectrum How can we get such precision performance from small tuning diodes a very ordinary shielded coil and a transistor with its supporting capacitors and resistors We assume already that the answer must lie in the functions of the Frequency Synthesizer IC However the key to grasping what this IC really does lies in grasping TWO concepts frequency synthesis and the Phased Locked Loop or PLL The more of a handle that you can get on these two interconnected ideas the less mysterious will be your FX transceiver as well most other modern radio gear from ham transceivers to car stereos to cellular phones To begin let s over simplify as much as we can UNDERSTANDING THE PLL In the following block diagram the notion of Loop is seen in the simple fact that the VCO output is routed right back into the VCO itself via the other circuit sections Try to imagine the
78. ets two or more inputs and delivers a single output The output is equal to the sum of the input frequencies and also to the difference between them MODULATION See also CW FM Modulation is simply the process of imposing variations on a steady RF signal from an audio source such as voice music or data see AFSK FX50 41 MUTE to turn off to render silent See also SQUELCH N can be any number to solve in a classroom problem but N is THE magic number decimal to understand in FX binary frequency programming N the frequency in KHz divided by 5 KHz NBFM Narrow Band FM NE prefix to transistors or IC s made by Signetics Inc OFFSET The distance in KHz or MHz of the transmitted signal from the primary or received signal The TX Offset may be higher or lower depending on the repeater setup or other application OP AMP Operational Amplifier a high performance linear amplifier with an Inverting input a Non inverting Input and one Output ORIENT orientation Yes the Orient is Marco Polo s Far East where they build many FM radios and where we buy many common parts When we ask you to orient a kit part one way or the other we re just asking you to get it RIGHT per all the orientation illustrations that we provide PACKET Rapid transmission of intelligible computer generated data in groups or bursts of a fixed length called packets PHASE DETECTOR In a frequency synthesizer the pha
79. he part s MUST be returned to us in suitable condition for testing Please be aware that testing can usually determine if the part was truly defective or damaged by assembly or usage Don t be afraid to tell us that you blew it We re all human in most cases replacement parts are very reasonably priced 2 MISSING PARTS Ramsey Electronics project kits are packed with pride in the U S A If you believe we packed an incorrect part or omitted a part clearly indicated in your assembly manual as supplied with the basic kit by Ramsey please write us with information on the part you need and proof of the kit purchase Before assuming a part value is incorrect check the parts list carefully to see if it is a critical value such as a specific coil or IC or whether a range of values is suitable such as 100 to 500 ufd Often common sense will solve a mysterious missing part problem If you are missing five 10K ohm resistors and find five extra 1K resistors a simple VOM check will likely confirm that the 1K resistors are actually the missing 10K units Hmmm guess the red band really does look orange 3 FACTORY REPAIR OF ASSEMBLED KITS To qualify for Ramsey Electronics factory repair kits MUST 1 NOT be assembled with acid core solder or flux 2 NOT be modified in any manner 3 BE returned in fully assembled form not partially assembled 4 BE accompanied by payment of the proper repair fee No repair will be begun until we have re
80. his is the last of Decimal numbers in this work We ll have to work with Binary numbers now In brief we set up the complement or exact inverse of N in binary and then add 1 This will give us our two s complement that is needed for programming into our offset matrix Binary code for N 200 8192 4096 2048 1024 512 256 128 64 32 16 8 0 0 0 0 0 0 1 1 0 0 1 FX50 35 Now just INVERT all of the bits 1 1 1 1 1 1 0 0 1 1 0 Then ADD 1 1 1 1 1 1 1 0 0 1 1 1 This is our two s complement alue which we program into our offset matrix You ll see these diodes in the position for 1 0 MHz TX offset Even though it appears that we are adding a huge N number to the original transmitter frequency the binary adders will follow the rules of binary addition and provide the proper programming information to the PLL synthesizer EXAMPLE 2 RECEIVER OSCILLATOR FREQUENCY We know from previous circuit discussion that the PLL synthesizer must run 21 4 MHz lower when in receive mode Two things must be done to do this first we switch out varactor diode D3 to allow the VCO L C circuitry to tune 21 4 MHz lower and secondly program in a minus 21 4 MHz offset to the synthesizer This offset is permanently programmed into the matrix because the 21 4 MHz 1st IF is integral to the FX receiver design Look closely at the Receive offset diode row and see why the diodes are installed the way they are N 21400 5 KHz 4 280 8192 4096 2048
81. iety of techniques are possible for binary programming of U6 s 16 parallel inputs We focus on the diode programming approach with some brief suggestions on externally controlled switching It is very intentional on our part to leave innovative programming schemes up to FX transceiver users because there s no single best way to do it for everybody There are several methods for quickly finding the required binary code for a FX 50 24 FX50 109 4 Set frequency to the channel you selected for 52 525 MHz Simplex FX 50 108 particular frequency and its N number 1 Descending Subtraction see Programming Worksheet 2 Printed reference lists see Popular 6 Meter Frequency Pairs 3 Computer programs see our sample BASIC program We recommend strongly that you fully understand how to make the calculation yourself because that is your ONLY means for checking the accuracy of printed information computer programs or the operation of experimental programming circuits Even though there are 16 matrix positions to program there are some shortcuts to make the job easier for normal ham band operation Consider the upper and lower band edges Notice the values of the highest 4 and lowest 2 positions are the same throughout the band We still must program in those six positions but we only need to calculate for the remaining 10 512 through 1 to program any 6 meter frequency desired The simplex calling frequency of 52 525 MHz is the dem
82. ing transmitter RF from the receiver circuit For maximum protection of the more delicate receiver circuitry D2 is turned on during transmit to short any stray RF directly to ground FX50 77 Stage DR Receiver Tuned RF Input and Preamp N7 FLIP sig ez eg 0 og gt og 6 0 og 0g p D oco og o o o OAS RA O 37 Q0009000 B 000 E EHRE PEANO 32 I 3 a A D N R26 E RZ Scam RB a ES FX 50 76 11 12 13 14 15 16 17 18 19 20 21 at the factory have tried to help by grouping similar or related parts in individual sealed bags Sorting organizers popular among kit builders include empty egg cartons muffin tins small box tops or the corrugated edges of box cartons Since the assembly of this kit is presented in distinct stages some builders may prefer to group their parts by stage before beginning assembly HELPFUL HINT Many of the parts are supplied on tape strips cut from bulk reels Leave them taped which keeps them nicely sorted for you It is NOT necessary to pull the entire lengths of both leads from the tape Simply nip the leads right at the edge of the tape and you ll have plenty of length to work with The 01 disc capacitors may be marked in any of the following ways 01 103 or 10n nanofarads Similarly 001 ufd discs may be marked 001 102 or 1n nanofarads The several 1 uf units required should be cl
83. ints Any 10 MHz segment between 50 and 60 MHz Diode programmable PLL synthesis 12 front panel selected frequency pairs easily expandable by switches microprocessors computers etc 5 KHz steps with programmable offsets Programmable Simplex 1 0 1 0 Aux NBFM All rates incl 9600 baud 5 pin DIN jack TXD RXD PTT 12VDC GND Speaker discriminator or true FSK 13 6V DC 10 Negative ground 1 0 A Transmit for 5 watts RF output 200 ma Receive no signal 50 ohms 600 ohms or high impedance PIN diodes Solid State for standard ICOM type speaker mic connection 10 IC s 16 transistors 24 diodes plus programming diodes 4 6 watts RF MRF237 or equivalent True direct FM 25 KHz 5 KHz NBFM Less than 5 Double conversion superhet First IF 21 4 MHz Second IF 455 KHz 12 db SINAD less than 0 35 uv 7 KHz 6db 15 KHz 60db Less than 0 25 uv More than 2 0 watts COR PL tone input FSK demod 12V 8V PLL programming FX50 5 INTRODUCTION to FX series VHF Transceiver Kit Assembly For the 1990 s Ramsey Electronics has adopted a Learn As You Build philosophy for ALL our electronics kits We feel that licensed ham operators should know about the equipment they use and also should have the desire to understand how their gear works Additionally it has been our corporate response to all those urgings by public officials that both students and their parents need to become
84. iode observe correct placement of the cathode band TX38 Install C20 82 pf TX39 Install C28 220 pf TX40 Install C30 100 pf R R amp RRA TX41 Install L3 the 7 1 2 turn coil prepared in stage TC Insertion will require you to spread the windings slightly to fit the holes When mounting these coils do not allow the wire spirals to contact the PC board ground plane area under them The coil must sit slightly above the board and not short against it TX42 Fabricate R113 Locate a 1K resistor brown black red Cut one lead to a length of 1 4 and bend it into a small loop as shown Carefully hold it straight while soldering it to the board This loop will provide a handy point to attach a meter probe TX43 Install C27 Locate an 82 pf capacitor bend out its leads away from L3 the body and insert one lead into the PC board and solder Its other lead will connect to the main PC board later D4 1X44 Locate two scrap component leads at least 1 2 long Solder each lead to the PC board as shown these leads will also attach C30 to the main PC board This completes the assembly of the low pass filter PC board inspect the board to be sure all leads on the bare side of the board are trimmed neatly and that the coil does not short against the PC board ground plane I c27 TX45 Exactly when to install the SO 239 antenna RF connector is left to your discretion If you are using your own case you must
85. irtual capacitance effect of a much larger device Stage G The FX Transceiver Synthesizer PLL The MC145152 IC incorporates the equivalent of 8000 individual transistors and contains the following circuits A crystal reference oscillator governed by Y2 10 24 MHz A counter or frequency divider circuit set externally to divide the crystal oscillator output by 2048 for a Reference Frequency output of 5 KHz A second counter or frequency divider that divides the frequency from the Prescaler U3 by the externally programmed number that we call N A third frequency divider A also used for programming Control logic circuitry which permit the N and A counters to work together for channel programming The Phase Detector or phase corrector which compares the 5 KHz Reference Frequency with the intended 5 KHz output of the N divider and sends correcting pulses to the VCO to keep the output of the Ndivider right at 5 KHz A lock detect signal circuit The reference oscillator is internal to U6 governed by Y2 The precision of the 10 240 MHz reference oscillator can be adjusted by trimmer C81 The R divider feeds 5 KHz to the phase detector section of U6 10240 KHz divided by 2048 The output of the MC12017 A64 65 prescaler U3 is AC coupled via C57 to pin 1 U3 is a dual modulus prescaler controlled by pin 9 of U6 The prescaled output of the VCO is fed to the A and N counters The N number programmed on
86. ised to select offsets 4 Programming Shortcuts are possible for ham band operation See text FX XCVR RIBBON CABLE 1N914 SWITCH TRANSCEIVER EXTERNAL PC BOARD MOA giron CONNECTION 1 3 Tr o 2 _ 1m o 8 32 ean See Ee a a j 512 ca oo a a 2 Ke a 8k 16K o 32 K oro RPT RPT Ee SIMP o o see _ a ar FX 50 38 G17a Insert and solder U9 as in step G15a G18a Insert and solder U10 as in step G15a Soldering the remaining pins for U7 U8 U9 and U10 may be done either as a single operation or at any other pace preferred by you to ensure careful work no missed pins no solder bridges As you complete the soldering of each IC mark its respective assembly step G15b 14 pins soldered on U7 G16b 14 pins soldered on U8 G17b 14 pins soldered on U9 G18b 14 pins soldered on U10 Install the following resistors and capacitors G19 R55 upright 10K brown black orange G20 R44 upright 22K red red orange G21 R53 upright 22K red red orange G22 C69 01 uf G23 C68 047 or 05 uf marked 047 or 473 or 05 or 503 G24 C91 047 or 05 uf G25 C98 01 uf G26 R43 upright 22K red red orange G27 R52 also 22K G28 R103 upright 47K yellow violet orange G29 R104 upright 10K G30 R90 upright 10K G31 R47 upright 10K G32 R102 upright 10K G33 R48 upright 10K G34 Install C85 1 uf marked
87. itch in the jumper area EL a 3 eS itself VRZ SQLELCH OY R26 E Scans Use this space to diagram your TNC cable connection Da ZLI 9 ES PACKET w j Na TPE DRAW YOUR TNC FX 50 116 FX50 17 RAMSEY FX SERIES FM TRANSCEIVER With emphasis on the PLL and VCO ES ve ES DMVIDE PHASE DETECTOR 2048 Swern BYN SYNTHESIZED PROGRAMM INO ER SHUR EY MC13135 DLAL CONVERSION FM RECEIVER IC TX RX PIN SWITCH o D7 MICROPHONE FX 50 18 Assembly Stage TO Programming Standard Repeater Offsets 1 0 and 1 0 KHz If you did not go ahead and do so when setting up the PLL Synthesizer for receiver testing in Stage H now would be a good time to install the diode programming for the standard transmit offsets We discuss Auxiliary or Non Standard offsets in the Reference section of this book page 34 36 The following programming will set up your transceiver for normal 6 Meter band operation still leaving the AUX line for programming one non standard split If you have an unusual application requiring more than one non standard split you will have to give up one or more standard or 1 0 MHz splits TO1 Referring back to Stage H as needed prepare three 3 long diode bridges for the offset matrix TO2 Install these 3 bus wire bridges in the RPT RPT and AUX lines TO3 For 1 0 MHz TX dffset install 9 diodes in the positions clearly marked
88. ix RPT RECV and other minus offsets are calculated by straightforward 2 s Complement binary addition See Stage H for examples Stage M Microphone Amplifier and PTT Circuit FX50 25 U4 is a LM324 quad op amp two are used as a conventional microphone gain amplifier and the other two are used in the PTT push to talk circuit FX 50 26 Chart X indicates the installation of a diode in that position Each one of these channels also requires a diode installed at the Simplex position Before installing diodes please be sure that you understand the principles of binary programming explained in detail in the first pages of this Section In lieu of constructing diode bridges and wiring the channel selector switch you may elect to build your own switching system using DIP slide or toggle switches Do such projects only after your transceiver is finished and working Channel Switch S2 may be installed at whatever point in the procedure that is most CHANNEL SWITCH convenient for you Its purpose is to apply 5V to the desired diode bridge Connect the desired channel positions on the switch to corresponding matrix channel rows using 2 lengths of hookup wire For all channels installed at this point that you intend for actual 6 Meter band communication remember to install a diode in the correct position for Simplex RPT or RPT Install in only one position for any given channel Remember that the Receiver Fre
89. lar IC the MC3359 as the heart of our popular FM receivers for the 10 6 2 and 1 25 Meter bands We adopted the MC13135 IC for the FXseries because of its features especially suited for state of the art FM voice and digital communications requirements The MC13135 is a complete FM narrowband receiver from antenna input pin 22 to audio preamp output pin 17 The low voltage dual conversion design results in low power drain excellent sensitivity and good image rejection in narrowband voice and data link applications The FX 50 implementation of this IC yields increased image rejection by using a 21 4 MHz first IF rather than the traditional 10 7 MHz A precision 2 pole crystal filter FL1 is used for the 21 4 MHz first IF The receiver IC is so complete that it includes an internal local oscillator requiring only a crystal across pins 5 and 6 to establish the basic operating frequency Our design injects the output of the transceiver s PLL controlled VCO through C35 As an option a helical resonator module can be installed in the front end RF amplifier area for excellent receiver performance in high RF environments The first mixer amplifies the signal and converts this RF input to 21 4 MHz This IF signal is sent to the second internal mixer via pin 18 where the 2nd IF frequency of 455 KHz is achieved by mixing with the 21 855 MHz oscillator The oscillator circuit is internal to U1 the crystal is Y1 21 855 MHz The 455 KHz second IF o
90. le marked 8R near Q13 R112 to the hole marked 8V near C29 In lieu of the switching done by the PTT circuit Stage M this temporary jumper applies 8V to all 8R points on the board You also have of course the option of wiring the microphone input and PTT circuitry before testing the receiver OPTIONAL VCO RECEIVER TEST OR INSTRUCTIONAL DEMONSTRATION At this point in building your transceiver the VCO is functional but is lacking any control voltage to varactor diode D3 that would permit tuning Supplying this precision controlled voltage is of course the function of the PLL Frequency Synthesizer that will be constructed next However for those who would benefit from such a test or demonstration it IS fairly easy at this point to set up temporary manual or analog tuning with an ordinary potentiometer Notice on the schematic diagram that the control voltage to the tuning diodes comes from USA through R47 and R25 Notice that a Test Point TP1 is conveniently located at R25 The purpose of TP1 is to permit measurement of the precision voltage to the varactor diodes generated by the frequency synthesizer s phase detector Since no such voltage is yet reaching TP1 we can put it there ourselves If we connect a potentiometer as illustrated below the wire soldered to TP1 can be trimmed down later to serve as the intended test point The potentiometer will vary the voltage to D3 thereby varying the VCO frequency and tuning your
91. ltage applied to varactor diodes which change capacitance in step with the voltage level ZENER DIODE a diode designed to have a very specific reverse breakdown voltage This property makes the Zener diode ideal for simple voltage regulators or precise voltage drop elements FX 50 44 Stage G The FX Transceiver PLL Synthesizer A reassuring feature of the FX Transceiver is that if you build it correctly and make just a few adjustments it will work fine whether you understand how it works or not For most amateurs and beginners the functions of the PLL Frequency Synthesizer and VCO will present the greatest challenge to understanding In fact these stages which are at the heart of the transceiver s design are not easy to explain in everyday terms because some level of engineering training or serious amateur curiosity is definitely required to catch on to the many concepts and principles involved In short don t feel bad if the functions of U5 through U10 seem somewhat mysterious to you at first The author s suggestion is that you study the FX transceiver s more complex sections simply for the fun and satisfaction of it catching on to a little bit here or a new concept there as you go along You ll get some insights from our published circuit descriptions and you ll pick up more from studying other publications such as the ARRL HANDBOOK discussing the circuit with friends with engineering backgrounds or doing whatever helps you b
92. mmended The PIN T R diodes D7 D6 and D2 are discussed in section DR In brief review D7 passes RF to J3 during transmit while D2 and D6 protect the receiver RF input The antenna input is designed for a 50 ohm resonant antenna C75 and C74 are tuned for maximum RF output 4 to 6 watts These adjustments are part of final transmitter alignment Maximum RF output depends critically on following the coil winding instructions EXACTLY in Stage TC Stage TX TRANSMITTER SECTION ASSEMBLY Install the components in the order recommended and DO NOT under any circumstances connect DC power to the unit unless instructed to do so ata particular point The following assembly steps presume that Stage TC RF coil and choke preparation was done Refer to TC if you have any question on these parts which also may be built up as you proceed IMPORTANT DO NOT install any parts near Q8 until after Q8 has been installed in accord with the explicit directions in Step TX2 If you fail to observe this caution it will be virtually impossible to perform the installation of Q8 correctly DO NOT INSTALL L9 R32 or L10 UNTIL AFTER ALIGNMENT HAS BEEN COMPLETED FX50 117 Stage TX Transmitter Buffer and Final Amplifier VHF PACKET DATA OPERATION oe elte vio og 1 Your FM transceiver was planned and designed to accommodate easy and reliable VHF packet radio operation 3 07 9 cog L og o o og o og o p o oc o oZ 0 oo OAS
93. n the temporary tuning potentiometer See if you can hear a local repeater or a nearby transmitter Because the control is sweeping through twenty MHz of spectrum actually tuning in a station will be VERY touchy Since the 6 meter band is sparsely populated it may be difficult to chance upon a signal without first setting up a QSO The demonstration can be more interesting and useful if a digital voltmeter is added to monitor the voltage changes at TP1 and a Ramsey Frequency Counter is connected to TP2 or the top of R113 REMEMBER that the indicated VCO frequency is 21 400 MHz lower than any signal you happen to tune in Observe how much frequency change there is per 1 volt or less of voltage change Stay on a given frequency for a minute or so and notice how the indicated frequency drifts slightly either up or down This observation helps us appreciate the precision control that will be offered by the PLL circuit Finally notice that the higher the voltage applied the lower the varactor diode s capacitance which means the higher the VCO frequency If you do have a meter and counter connected an initial setting of the slug in L7 can be made now Adjust the voltage for 4 0 volts and tune L7 to approximately 52 MHz Note final tuning of L7 will be even easier after the PLL circuitry is completed When you are finished with this optional test disconnect DC voltage Then cut the wire to TP1 leaving 1 4 soldered in place to serve as a perman
94. ndamental digital operation after being in a binary high or low on or off state is to be able to find the sum of such states from two or more sources The BINARY ADDER performs this function See also BINARY AFSK Audio Frequency Shift Keying SEE FSK In short this is a very popular form of data transmission AXIAL LEAD Wires stretch out from two opposite ends of a part instead of from one end i e along the axis of the body For example L20 BA Manufacturer s PREFIX for PIN type diodes BASIC Basic We re talking about the one computer programming procedure that should make sense to ALL computer owners If any further explanation is needed visit a library or computer dealer BB Manufacturer s PREFIX for VARACTOR diodes BINARY the number system based on the two values of 0 and 1 Here are all the tables that we need to memorize 0 0 0 0 1 1 1 1 0 and carry 1 to next position BOARD Generally refers to PC board or printed circuit board BUFFER An electronic circuit stage a sort of referee that tells its input and output not to mess with each other Think about such a task It may also provide amplified output of the incoming signal CASCADE cascading combining two or more identical circuit elements or components for improved effectiveness CARRIER Transmitted RF signal that is NOT modulated It is heard as a steady tone on BFO equipped receivers or as a powerful silence i e ov
95. nexpensive to build yourself FX 50 8 Step 8 regarding FM Deviation Remember that indicated RF output also depends on the accuracy of the wattmeter and correct DC supply voltage Our lab measurements consistently show 5 watts or better TX52 Replace the dummy load with a well designed 6 Meter antenna and start enjoying the FM transceiver that you built yourself IMPORTANT It is your responsibility to know what band privileges are granted by your Amateur Radio License and how to program the frequency synthesizer correctly within the 50 to 54 MHz operating range of the 6 Meter Amateur Band A proper license is required for transmitting in this band Other FCC licensing is required for operation of this equipment on frequencies outside the Amateur Band It is illegal for licensed amateurs or other persons to transmit on frequencies for which they are not properly licensed RAMSEY ELECTRONICS INC FX50 125 4 40 nuts TX46 Line up the two ground wires and C27 the 82 uf coupling capacitor on the low 4 40 screw pass filter board with the mating holes on the main FX PC board Allow the low pass board to stand about 1 8 above the main FX board and at a neat right angle Solder the leads to VA the main FX board be careful ye so as to not loosen the solder 50239 Female joints on the little board from too Case Panel much heat when soldering if you do just retouch the solder joints again it s no big deal S
96. not lose any or confuse them Leave parts supplied on tape strips in the strips until you need them The following headings also provide logical sorting categories Popular methods for organizing parts include egg cartons muffin tins corrugated cardboard edges or pressing the leads into a block of Styrofoam INTEGRATED CIRCUITS MC13135 24 pin DIP FM Receiver IC U1 LM380 14 pin DIP Audio Amplifier IC U2 Do NOT use socket MC12017P 8 pin DIP divide by 64 65 Prescaler U3 LM324 14 pin DIP Quad Op amp IC U4 LM358 8 pin DIP Dual Op amp IC U5 MC145152 28 pin DIP PLL Synthesizer IC U6 74HC283 16 pin high speed 4 bit Binary Adder U7 U8 U9 U10 7808 8V voltage regulator VR1 7805 5V voltage regulator VR2 La a ea a ge ee eee ee ee os TRANSISTORS 7 NPN transistor type 2N3904 or equivalent Q1 4 5 6 7 11 15 3 PNP transistor 2N3906 type marked 228256 Q12 13 14 2 NPN VHF type 2SC2498 or 2570 Q2 3 Sort these carefully from the 5 type 2N3904 for Q1 etc 1 RF NPN type 2N3866 transmit driver Q9 1 RF NPN type MRF237 or SD1127 transmit final Q8 RR DIODES Note color code descriptions CARE FULLY 1 LED D17 transmit indicator 100 1N914 or 1N4148 switching diode D4 5 8 9 10 11 12 13 14 15 16 19 22 24 plus PLL matrix 1 Varactor diode type FS4059 D3 black body with yellow band 1 PIN diode type BA479 D6 3 PIN diode type BA482 D1 D2 D7 orange body red band 1 1N4002 rectifier
97. nsceiver is designed to help your radio survive quite a wide variety of imperfections It s not a power supply in itself but it comes close because it performs all the essential functions expected from a good solid state DC source Just add 12 15VDC from a battery vehicle or bench supply Much of the circuitry operates on the regulated 8 volts supplied by voltage regulator VR1 If you have already looked around the schematic diagram and also seen 8R or 8T these are points where the regulated 8V output is switched for Receive or Transmit by the PTT push to talk circuitry Q12 U4c U4d Q13 Q14 which we ll discuss in more detail when it s time to build it in Stage M The Receiver IC U1 and the digital frequency synthesis circuit is powered by 5 volts regulated by VR2 The op amps used in the circuit U4 and U5 operate from this single supply through the use of voltage divider networks at the respective IC s The full 12 15 volt input is supplied to the transmitter RF output section and to the receiver audio amplifier U2 The large 1500 uf capacitor C42 and inductor L20 are installed at the DC input to filter out ignition noise etc Fuse F1 is contained in the power cord and the DC power switch is integral to the volume control The DC negative black wire is soldered directly to the PC board ground plane The Packet Connector The Packet I O Jack J1 is not a stage or section of your transceiver in itself It is simply a c
98. nstall D5 1N4148 style signal diode Observe correct orientation of the cathode band LN E17 Solder 1 2 lengths of bare wire trimmed from resistors or capacitors in the two test point holes marked TP1 and TP3 These wires stick up from the PC board and provide a convenient point to connect a test probe 18 Install C57 01 uf 7b E19 Install U3 MC12017 If you ve elected to use sockets do not use a socket for this part Be sure to observe correct orientation of this part FX50 83 The control voltage for D3 the varactor diode is supplied through R47 and R25 by the output of U5 A in the PLL synthesizer circuit We know already that there must be a 21 4 MHz difference between the receive and transmit frequencies of the VCO This swing cannot be accomplished by PLL programming alone The VCO must be able to stay in range with the synthesizer Inductors L6 and L7 work in series during receive which increases their total inductance to the VCO circuit and more inductance means a lower frequency In transmit mode PIN diode D1 is turned on thus shunting VCO coil L7 to ground directly bypassing L6 s additional inductance This causes the VCO to be able to tune higher in frequency and is accomplished by transistor switch Q5 The output from Q7 is fed into U3 MC12017P a A64 65 prescaler which divides down the VHF signal to a lower frequency which the PLL chip can process The VCO U1 through C35 for receive and Q1
99. nt of 1 s 5 The CLEAR instruction after screen printing is important if it is omitted AA BB CC etc will not be reset for checking the next frequency 6 Innovative computer programs to enhance enjoyment of the FX transceivers are encouraged send them to your favorite ham or computer magazine newsletter or BBS 7 LPRINT or equivalent Basic statements can be used to produce hard copy printouts of frequency information you need 8 IMPORTANT Before soldering ANY diodes in your FX transceiver programming matrix per this program CHECK AND VERIFY that your program is giving CORRECT results COMPARE it to the samples in this book NOTICE Although this program has been tested on many Microsoft BASIC releases including GW Basic it is printed here solely as a convenience and is not integral to the Ramsey FX 50 operation If you have trouble running the program please get help from a local computer friend and not from the Ramsey factory we re radio guys not computer hackers FX 50 31 Sample BASIC Program Listing 50 PRINT Enter Receiver Frequency as 6 digits with NO decimal 52 INPUT For example 146520 Enter here F 55 N F 5 60 PRINT The FX146 or FX220 N number for binary conversion is 101 AA 0 102 BB 0 103 CC 0 104 DD 0 105 EE 0 106 FF 0 107 GG 0 108 HH 0 109 I1 0 110 JJ 0 111 KK 0 112 LL 0 113 MM 0 114 NN 0 115 OO 0 116 PP 0 200 IF N gt 32768 THEN AA 1 205 IF
100. nt semiconductors are needed FX50 49 The RAMSEY FX Transceiver Kit WARRANTY Please read carefully BEFORE calling or writing in about your Kit Most problems can be solved WITHOUT contacting the Factory Notice that this is not a fine print warranty We want you to understand your rights and ours too All Ramsey kits will work if assembled properly The very fact that your kit includes this manual is your assurance that a team of knowledgeable people have field tested several copies of this kit straight from the Ramsey inventory If you need help please read through the manual carefully all information required to properly build and test your kit is contained within its pages In particular the FX Transceiver has been documented exhaustively 1 DEFECTIVE PARTS It s always easiest to blame a part for a problem in your kit Before you conclude that a part may be bad thoroughly check your work Today s semiconductors and passive components have reached incredibly high reliability levels and it s sad to say that our human construction skills have not Very rarely a sour component might slip through All our kit parts carry the Ramsey Electronics Warranty that they are free from defects for a full 90 days from the date of purchase Defective parts will be replaced at our expense If you suspect a part to be defective please mail it to our factory for testing and replacement Please send only the defectiv e part s NOT the entire kit T
101. nual where you feel the possible fault could be A thorough understanding of each circuit just may help after all FX 50 127 FX 50 126 parts as a finished product For a minimal investment of your time as well as your well earned money you will have a VHF FM voice data transceiver that you will truly own Real owning ultimately means knowing how to maintain and understand something that we have in contrast to merely possessing a thing because you spent the bucks to do so You ll have the flexibility of 12 channels chosen by YOU with the easy ability to change or expand You ll have both FM voice and high speed data capability When you re ready you can experiment with many different enhancements concentrating on those truly useful to you If there s ever a problem you won t think twice about digging in and fixing it Whenever you decide you could use still another VHF UHF FM data transceiver at a budget price you ll know with confidence that an FXseries kit is the right way to go What s faster turning your FX Transceiver to any one of 12 possible channels programmed by you or trying to remember again exactly how to use the memory pre sets of your HT or your HF rig or the VCR or the microwave Let s learn about and build up an FX VHF FM Transceiver FX50 7 A MESSAGE TO HAM RADIO BEGINNERS If you have just earned your Novice or Technician license or are studying for either of them right now we d like to say a
102. of not two but three functions which could involve three conductors and a more complex jack Three functions First we need to supply audio output from the microphone element to the amplifier Next we need some kind of PTT switching connection Third the electret microphone itself needs a small amount of voltage to operate its internal FET source follower transistor Here s how we do it with one mike line Pushing the button simply connects the microphone element to the line About 2 volts through R60 and R57 operate the microphone element which sends audio through C83 to U4A PNP transistor Q12 senses the tiny current draw of the microphone element and switches the 8 volts at the emitter through to the collector To state it very simply the output of U4 turns off PNP Q13 which had been supplying 8 volts to all 8R points of the circuit And the output of U4C switches on PNP Q14 to supply all 8T points Diodes D11 and D12 assure positive action that Q13 and Q14 are fully on or fully off when the op amp outputs swing Releasing the mike button instantly reverses the status of Q12 Q13 and Q14 to return to receive mode FX 50 110 The VCO requires a very pure source of well filtered DC free of AC hum alternator whine or other disturbance R19 and the 47 uf C40 form a basic low pass filter Transistor Q4 serves as an electronic capacitance multiplier The actual effect of the filter is that the beta of Q4 multiplies the 47 uf fora v
103. of the MC12017P 64 65 prescaler U3 is AC coupled via C57 to pin 1 IC U3 is a dual modulus prescaler controlled by pin 9 of U6 The pre scaled output of the VCO is fed to the A and N counters The N number programmed on the diode matrix is pre determined to divide this frequency down to 5 KHz for phase comparison with the 5 KHz output of the crystal controlled reference divider The minimum N number is 1 The maximum can be stated in a variety of ways some more exact than others We could just say 64K less 1 or 2 to an n th power less one We could say the maximum is what you get when you install diodes in all 16 positions of the parallel programming matrix We could express it as 2 x 32768 1 or just say that it is 65 535 The details of N divider programming will be covered in the next section We ll even see that the roles of the offset matrix and the binary adders U7 U10 are clear brief and simple to explain FX 50 92 to RF ground the horizontal elements are called a groundplane HIGH In solid state circuitry to say a given device pin or circuit point is at a logic high is to say that it shows a DC supply voltage at that point Switching to the opposite state LOW or back again for some specific purpose is a fundamental capability of the circuit HOUSE NUMBER A manufacturer s part number different from the industry standard description of a part Example LB53303HK L1 HYSTERESIS the ability of an
104. ommon faults Coils touching the board Solder shorts between components Solder short on Q8 base to ground 2 Low Output Power We see 4 6 watts normally If your figures are within 20 consider this ok a Ensure DC input to the transceiver is a full 13 8 VDC If your lead wires are too long they could be dropping excess voltage Check for proper voltage on the board not at the power supply b Ensure 8T is a full 8VDC This is the supply voltage for the transmit Buffer c Try adjusting the coils slightly and then retuning for maximum power output L2 L3 L12 L13 and L14 are purposely designed to have extra inductance so you can peak the power output by spreading the coils Common faults Low supply voltage Improper tuning FX50 129 VCO amp PLL Faults manual pages 21 24 82 89 90 97 1 PLL not locking L7 will not set correct voltage TP1 a Check for proper programming inputs to U6 pins 10 25 If incorrect fault lies between diode matrix and inputs to U6 VOLTAGES ON U6 52 525 MHZ IN RECEIVE TRANSMIT pin VDC pin VDC pin VDC pin VDC 20 0 0 16 5 5 12 0 0 24 0 5 19 0 0 15 0 0 11 5 0 22 0 0 18 0 5 14 0 0 10 0 0 21 0 0 17 5 0 13 0 5 25 5 0 23 5 5 b Check VCO for proper range of operation Follow the test on page assm 86 87 of your manual You will need to remove R47 for this test The VCO should tune smoothly from approx 30 Mhz
105. onstration and alignment standard for the FX 50 model N is quite easy to determine N for 52 525 MHz 10505 The placement of diodes in the Programmable Offset Matrix follows the same binary number principles as used for frequency programming This matrix is connected to the 16 programming inputs of U6 through the four 4 bit binary adders U7 U10 Fewer programming positions are provided on the board simply because there is no practical use for extremely large or very tiny offsets The 1 bit to 8K range provides plenty of flexibility for non standard channel spacing U7 through U10 are called 4 bit binary adders because they each can handle four binary addition operations For each bit there are A and B inputs and one S sum output Examine the schematic diagram closely and you will see that all the frequency programming lines are connected to A inputs and all offset lines go to B inputs Notice further that the binary positions of both matrixes correspond to each other exactly the 8K offset position goes to B1 of U7 and the 8K frequency programming position goes to A1 Their sum appears at S1 pin 1 and goes to U6 And so forth for all the other binary programming positions The programming for receive mode and standard repeater offsets is silk screened on the PC board itself Assembly Stage H explains the theory behind these positions The RPT N numbers are calculated in the same way as for the Frequency Programming matr
106. onvenient port to use computer terminology which gives a packet TNC terminal node controller convenient access to the microphone and receiver audio circuits We ll install J1 and its associated bypass capacitors at the beginning because now is as good a time as any and it gets some parts on your PC board quickly and easily Also having J1 in place will give a little extra protection to other parts when you are working on the solder side of the board FX 50 61 Stage A ASSEMBLY STEPS g A1 Strip 1 8 of insulation from the heavier gauge black wire insert and solder in the GROUND hole This connection may be soldered on the TOP side of the board as well as the solder side A2 Cut 8 of wire off one end of the inline fuse holder Save this wire for use in the VOLUME next step Strip 1 8 of insulation from the IN in line fuse wire and solder it to one of the S1 switch lugs of the volume control R7 ER The switch lugs are the two outermost of GND the 5 lugs A3 Strip 1 8 of insulation from each end of the 8 wire from the fuse holder saved in the last step Solder one end to the other switch lug on R7 and the other end to the PWR point on the PC board MAKE SURE that ALL strands of this wire are neatly inserted and soldered in the hole Any stray strand will cause a direct short when it touches the ground plane A4 Install L20 the 500 uH noise filter inductor It is the large cylinder shaped component with wires
107. optional in the previous section it is now time to put your completed receiver section through its paces In order to do this one or more receiving frequencies must be programmed on the primary matrix If you already have a firm plan for how you wish to program some or all of the channel positions you can proceed with making the frequency programming lines that you are sure about If you have little or no sure idea of how you want to set up the channel selector switch you can build up a simple switching system that will let you try any frequency of your choice H43 If you are unsure of what frequencies to program we suggest the following to get started Channel 1 52 525 MHz Simplex national calling frequency Channel 2 One additional simplex frequency Channel 3 Main repeater of your local radio club Channel 4 One additional repeater in your area Add more channels as you become more familiar with 6 Meter band operation in your area You can change or delete any of these frequencies whenever you wish Note Your PC board silkscreen may show diode placements that differ from your calculated placement Place diodes where you have calculated their position to be and ignore any silkscreen that does not agree with your diode placement Freq 32K 16K 8K 4K 2K 1K 512 256 128 64 32 16 8 4 2 1 MHz 52 525 g K g g g g g H44a Construct at least two diode bridges for frequency programming as illustra
108. orient the diodes correctly 53 57 W 10 714 1 Install the following resistors 53 59 10 718 1 H1 R68 1K brownblack red 53 61 10 722 1 53 63 10 726 1 H2 R69 1K brown black red 53 65 10 730 1 H3 R114 1K brown black red 53 67 10 734 1 H4 R65 1K brown black red 53 69 10 738 1 H5 R67 10K brown black orange 53 71 o 10 742 1 53 73 10 746 1 0 0 0 0 0 0 0 0 0 0 0 0 Install the following diodes be sure to orient the cathode banded end sp ss O O O O O OF OF O OF O O O correctly Diodes are type 1N914 1N4148 53 75 10 750 1 0 H6 D19 53 77 a 10 754 1 0 53 79 10 758 1 0 pawn a 10 762 1 0 H8a D13 53 83 10 766 1 0 H8b D14 53 85 W 10 770 1 0 H9 D16 53 87 E 10 774 1 0 H10 Install NPN transistor Q15 type 2N3904 Watch correct orientation Doe il Weel S 53 98 10 786 1 0 Notice that a total of 33 identical 100K resistors brown black yellow are to 53 95 a 10 790 1 0 be installed in two rows for the two diode matrix areas of your transceiver If 53 97 10 794 the 100K resistors provided in your kit have pre shaped and trimmed wire aS Be 0 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 O O O O O O O O O O O O 0 1 1 1 0 0 0 0 1 1 1 1 0 0 0 0 1 1 1 1 0 0 0 0 0 0 0 0 0 1 1
109. orrect orientation of cathode band At this point all transceiving functions except final transmitter output power may be tested and aligned Q10 has plenty of RF output 10 milliwatts for a signal that can be heard in a nearby receiver or scanner You may test and align the transceiver now or do so after installing the remaining transmitter parts However DO NOT INSTALL L9 or L10 UNTIL AFTER ALIGNMENT HAS BEEN COMPLETED Whether you test now or later depends on how anxious you are to see and hear the results of all your hard work If you are still awaiting your ham license you can test the FM modulation of buffer stage Q10 and also enjoy your receiver fully Be aware however that the buffer stage even with no antenna connected to it has a transmitting range of about 100 feet even through walls and obstacles FX 50 120 resoldered after passing through the grommet Snap in the locking section of the relief grommet only AFTER both the red and black wires are in place 4 Remove the two screws from the SO 239 antenna connector gently bend the lugs as needed to match the rear panel holes then secure the jack and lugs to the rear panel 5 Since the top shell will not be needed until you re ready to go on the air keep it wrapped in protective material until you re really ready to use it 6 The side rails may be installed to the bottom section at any time To prevent loss of the screws for the top keep them loosely threaded in the
110. oughout this guide Keep in mind that due to differences in test equipment power supply voltage etc your readings may vary slightly Any voltage within 20 or so should be considered ok It may also be difficult to lead you to a specific component or fault right off Now clear off that workbench lock the doors put up the do not disturb sign and let s get started Preliminary Checks Many times these first few checks will solve the problem 1 Proper DC voltages 13 8VDC 8V 5V 8T 8R 2 Solder connections All joints should be clean shiny and solid You won t need a magnifying glass If a connection is suspect reflow the solder Also check for stray solder shorts or bridges 3 Easy to confuse items Now let s see was that a 10K ohm resistor or 1K ohm Some of those color bands look quite similar to tired eyes Let another pair of eyes check your work 4 Component lead length VERY IMPORTANT Make sure all component leads are as short as possible In other words pull the leads through the board until the component body rests on the board The hand wound coils of buss wire should not touch the board One exception obviously 5 Make sure only one channel is activated at a time A diode installed backwards in another channel can turn on two channels at once Your voltmeter should indicate voltage on only one bus wire at a time This is true for the offsets too 6 Reread those sections of the ma
111. ous about U3 its job is to divide the VCO s VHF output down so that U6 need only analyze count 1 64 of it in order to send voltage adjustments back to the VCO This prescaling keeps the input frequency to U6 within specifications Will the circle stay unbroken asks an old folksong If the PLL s circle of activity is broken by incorrect phasing the loop is said to be unlocked If all is going well the loop is locked The loop is UN locked only when the phase detector gets so unhappy that what is being fed into its two inputs is so far out of whack that it cannot make corrections If the loop is unlocked no useful control voltage reaches the VCO If the VCO operates at all it will be at a wrong or unknown frequency The phase detector can also be called a phase corrector It does more than just detect or look at the two incoming 5 KHz signals It sends correcting pulses to the VCO to keep it in phase with the 5 KHz output of the crystal reference oscillator A good word for understanding phase is synchronization or sync The process of tuning a musical instrument is a good illustration of sync or phase When two guitar strings are very close but not exactly on the same note there is a discernible third sound a sort of rumble that disappears as FX 50 90 QUADRATURE Refers to the Phase Angle 90 degrees considered by the FM discriminator or detector REFERENCE FREQUENCY a precise known frequency usually crystal
112. p U5 A sums together the phase detector outputs and the output of U5 A is passed through a network of 2 2 uf electrolytic capacitors C67 70 90 92 to smooth out the phase detector pulses to clean DC for controlling the VCO R47 R48 and C85 form yet another low pass filter to ensure that any 5 KHz whine will not get into the VCO Because the DC charge developed in C85 1 uf would slow down the PLL during major frequency swings such as going from transmit to receive D8 and D10 are set up back to back across voltage dropping R48 Whenever there is a major frequency shift which means a significant VCO control voltage change one way or the other one diode or the other is switched on to short out R48 and discharge C85 This lets the PLL re lock instantly C85 recharges and the diodes become no factor in the circuit The lock detect output pin 28 of this Motorola PLL IC is a fine feature that could be used many different ways in this circuit We could have set it up to tell an LED to alert you that you are UL unlucky unlocked Instead we decided to protect your investment in the transmitter RF section of your transceiver and keep our FCC smiling The lock detector gives a strong series of pulses when the PLL is unlocked When the PLL is locked only a tiny sawtooth wave appears at pin 28 The lock detect voltage is watched by U5 B If unlock pulses appear they are integrated through R90 and C96 as a fairly clean DC voltage charge b
113. pacer nut C27 Ground Jumper TRANSMITTER COMPLETION AND TUNEUP Do not proceed with the following until all of the previous steps have been completed successfully You now have a somewhat fragile assembly the rear panel being held to the main PC board with only three wires so please be careful during the next few steps TX47 Disconnect DC power and antenna TX48 Connect the following to your transceiver 50 ohm dummy load VHF RF wattmeter or voltmeter connected to R115 the stand up resistor test point on the low pass filter board DC 12 volts power X49 Press key the transmit button and alternately adjust C75 and C74 with a non metallic alignment tool for maximum RF output indicated on the meter If you are using a voltmeter connected to the resistor test point you will typically see about 12 to 15 volts when connected to a good 50 ohm load Keep these key down tests as brief as possible zs X50 If you are observing at least 4 watts of RF output transmitter tuneup is completed Spread coils L12 13 and L14 on the main board and L2 and L3 on the low pass board for maximum RF output These coils are purposefully wound with a little too much inductance so that they can be easily peaked by some spreading This is probably one of the most important steps to get the most RF out of your rig TX51 Adjust Modulation control R46 by listening on another receiver or scanner and simply adjust for best sounding
114. pulses to the VCO to keep the output of the N divider right at 5 KHz A lock detect signal circuit An easy illustration of how simple assembly error causes an unlocked or mistuned PLL can be seen in the fact that the Reference Frequency R counter is externally programmable by grounding various combinations of pins 4 5 6 permitting 8 possible divider values Let s say that pin 6 of the IC or socket is bent and does not make contact This would cause the R divider to divide by 1160 rather than 2048 for a Reference Frequency of 8 8276 KHz rather than 5 KHz Thus the VCO output would become a multiple of 8 8276 KHz If N is programmed as 10 505 for 52 525 MHz Simplex the single bent IC pin would cause the output frequency to be 10 505 X 8 8276 KHz which is 92 734 MHz Because the VCO cannot tune this high the loop becomes unlocked In addition to looking over the following block diagram of the internal circuits of U6 it is worthwhile to study the block diagram and the schematic of the whole FX transceiver circuit The more you work to understand it the more confident you ll become in using maintaining programming and customizing your FM transceiver FX TRANSCEIVER PLL OVERVIEW The reference oscillator is internal to U6 governed by Y2 The precision of the 10 240 MHz reference oscillator can be adjusted by trimmer C81 The R divider feeds 5 KHz to the phase detector section of U6 10 240 divided by 2048 The output
115. quency corresponds to a repeater s output and that you are using RPT or RPT to match the repeater s input frequency There is no need for diodes in the Simplex RPT or RPT on any channel intended only for listening Also be aware that omitting these diodes does not completely disable transmitting capability Be VERY careful and use common sense when monitoring outside the ham band RECEIVER ADJUSTMENT AND OPERATION At this point we assume that all preceding assembly steps have been completed for stages A through H and that Stages M and TX associated with the transmitter have NOT been done A jumper wire is still in place between 8R and 8V All IC s are installed except U4 Adjustment Procedure 1 Check PC board carefully for missed connections wire trimmings or untrimmed wires bent down etc 2 Connect speaker and DC supply voltage 3 Obtain or make a non metallic alignment blade capable of adjusting L7 and C81 FX 50 107 We have reached the mountain top in building the RECEIVE section of your transceiver as well as many sections or stages needed for transmitting and receiving Double check your work as needed Frequency Programming and Channel Switch Preparation Before completing the transmit functions of this VHF FM transceiver we should now verify that the PLL Frequency Synthesizer gives performance as desired and as designed Regardless of whether you pursued the VCO receiving tests proposed as
116. r and Final The transmitter section Q10 Q9 and Q8 is conventional VHF RF circuitry that has proven quite reliable in Ramsey transceivers Just a few circuit notes are in order Transistor Q10 the transmit Buffer amplifies the VCO output from C56 to about 10 milliwatts quite sufficient for checking modulation and PLL alignment in transmit mode as soon as this stage is built Operating bias is supplied by the PLL lock detect voltage from U5B through R110 If the PLL unlocks Q10 does not operate preventing the radiation of out of band signals The 2N3866 Driver Q9 amplifies the output of Q10 to drive Q8 to its full rated output Q8 the popular MRF237 or its equivalent has physical characteristics that the builder should understand Many RF transistors of this style have the Collector lead common to the case Through sophisticated insulating technology the Emitter lead is common to the case There is significantly better gain because there is no emitter lead length to speak of This relatively small transistor package can handle large power dissipation IF the case is properly soldered to the groundplane of the PC board as detailed in the assembly instructions The transistor is fully intended by the manufacturer to be heat sunk in this manner don t worry about soldering heat damaging the device DO NOT install any transmitter parts without at least reading over the assembly details first and the reasons for the sequence that we have reco
117. r than endorse or illustrate any particular scheme of which there are dozens if not hundreds we provide here the most basic schematic information needed to set up any kind of auxiliary switching correctly The principles and requirements remain the same whether you use DIP switches toggle or slide switches electronic latching or go all out to build the mother of all diode matrixes Make sure whatever you build resembles electrically the diagram on page 38 Some DO s and DON Ts of FX Transceiver Add Ons 1 DO study and understand the basic switching diagram 2 DO let your ingenuity run wild to come up with the neatest most cost effective scheme 3 Please DON T ask our technicians to talk you through your own idea 4 DON T run switching cables across the VCO and Transmit RF side of the PC board 5 Please DO submit successful frequency control ideas as articles for your favorite ham radio magazine Your pay as author may cover the cost of your transceiver 6 Please DO mail or fax us your good ideas 7 Please DON T try out ANY modifications of the basic FX Transceiver FX 50 37 unless you already have it WORKING fine NOTES 1 DIP switches with diodes can be installed on above the diode matrix itself for E Z internal programming changes 2 Any auxiliary programming device can be wired to a switched position on the FX transceiver matrix as well as to the auxiliary points illustrated 3 SPDT switching may be dev
118. re installed quite early in the assembly sequence so that tests can be conducted periodically during assembly The disadvantage of this approach is that there is considerable wear or strain on the various wire connections as the PC board is repeatedly flipped back and forth during assembly This is a serious consideration because more radios and computers malfunction because of broken wires than from electronic parts going bad For this very reason such wiring is ordinarily done as a final step in electronics assembly To minimize damage to the control and jack wiring use one of the provided wire cable ties to hold down this group of wires temporarily Loop the tie through the PC board mounting hole near U10 s position grouping the wires snugly to the board After fully assembling and testing the kit the tie may be clipped off allowing you to once again use the PC board mounting hole FX 50 74 FX50 59 Stage A DC Power Input Regulation and Distribution Plus Packet Radio 1 0 Connector J1 SIINOHLOTII AISWYY IESU U ISEE G a O ZAN 96 1 0s xX a W 7 og 0 LIe Zia bd o5 0 ogo o 0 og o oco op o o o oz o oL o O ont 2000690 one an RS Ei FX 50 60 c o J UW We S amp S N gt ogy 23 MZY So far most disc capacitors installed have been from your endless supply of 1 01 and 001 capacitors If you have not done so already now would be a
119. receiver VCO AND RECEIVER TEST PROCEDURE 1 Make sure work area is tidied up and that the PC board has been checked for stray scraps of wire etc 2 Use your own hookup wire and potentiometer to connect to TP1 8V and GND as illustrated 3 Turn power switch OFF and squelch fully counter clockwise Optional TEMPORARY VCO TUNING TEST RECEIVE ONLY B VOLTS 2K SK or 10K TP1 s POTENTIOMETER GROUND Higher Voltage Lower Capacitance Higer Frequency Lower Voltage Higher Capacitance Lower Frequency FX50 85 A A A ARA g E20 Install R19 1K ohm brown black red E21 Install C38 01 uf E22 Install C46 01 uf E23 Install C50 01 uf E24 Solder a 1 2 length of bare wire trimmed from a resistor or capacitor into the test point hole marked TP2 This is another test point E25 Install C21 27 pf marked 27 The previous steps were presented as a group primarily as a help in visualizing the location of the VCO on the PC board You have built up the VCO itself and the capacitance multiplier voltage filter provided by C40 Q4 etc After double checking the accuracy of your work proceed with installing the VCO related components in Stage F Stage F VCO Buffers PLL Synthesizer 65 64 Prescaler g BR A RA ARAR bo R O AO B R F1 Install Q4 2N3904 transistor Observe correct placement of the flat side F2 Install R18 270 ohms red violet brown F3 Install R23 1
120. respective IC s The full 12 15 volt input is supplied to the transmitter RF output section and to the audio amplifier U2 Components L20 and C42 provide ignition noise filtering The 5 pin DIN Packet I O Jack J1 has pinouts corresponding to current conventions for TNC s Receiver audio to pin 4 may be taken from the amplified speaker output or from the FM discriminator output or from the true FSK data output of U1 Selection is by a jumper wire on the PC board B Receiver Audio Amplifier The LM380 is a self contained general purpose audio amplifier capable of over 2 watts audio output with a voltage gain of 50 Audio from the FM discriminator U1 is fed through C7 through the 10K volume control R7 to pin 2 the amplifier input The amplified output at pin 8 is available through C34 to both the speaker jack and pin 4 of the Packet I O Jack C41 in series with R108 across this amplified output are good practice recommended to prevent self oscillation of the IC Pin 1 is bypassed to ground through C48 in normal operation If pin 1 is grounded directly the internal bias of the LM380 is upset and the amplifier is silenced Q6 is a simple switch When 8 volts is applied through R107 and D22 to the base of Q6 the transistor collector grounds pin 1 of U2 thus silencing the receiver during transmit The COR output of U1 pin 16 also mutes the amplifier FX50 19 FX 50 20 M37 R70 near front of PC board by the diode matrix 1
121. rom 9 9 8 1 Can we subtract 4 from 1 Can we subtract 2 from 1 Can we subtract 1 from 1 1 1 0 YES NO NO YES NO NO NO NO YES NO NO YES Therefore diode at 2048 Therefore NO diode at 1024 Therefore NO diode at 512 Therefore diode at 256 Therefore NO diode at 128 Therefore NO diode at 64 Therefore NO diode at 32 Therefore NO diode at 16 Therefore diode at 8 Therefore NO diode at 4 Therefore NO diode at 2 Therefore diode at 1 As soon as we get a result of 0 we are finished and the remaining positions are left empty indicating a zero Let s check our results using this shortcut method On the previous page we found the binary equal of N 10 505 was 0010100100001001 And just now we find the binary value of N to be 0010100100001001 We see that this way leads us to a correct result also We could go on and on with shortcuts and tips For example we can just know in our heads that the 1 position is used only for frequencies with 5 KHz spacing The most important thing is simply to become comfortable and accurate in converting N to its binary equivalent FX 50 101 Even though there are 16 matrix positions to program there are some ae a Re a i shortcuts to make your job easier for normal ham band operation Let s look 326 IF NL lt amp THEN NM NL at the upper and lower band edges for the 6 Meter band 330 IF NM gt 4 THEN NN 1 335 IF NM gt 4 THEN NX NM 4
122. rovided with this transceiver kit HEIGHT ABOVE BOARD 25 IN LENGTH 2 375 REV O oo0no0o a RPT 5 __8 9 8 6 6 6 4 PT B E Q AX 8909090 Form ond install all 4 bridges at thie time if yau wish H42b Set the PC board across two small boxes blocks cups or any objects which provides a couple inches of clearance between the bottom solder side and your work surface H42c Stand the CATHODE dark band ends of the seven diodes down into these positions only on the RECV row of the smaller matrix 8 64 256 512 1K 2k 8K H42d Join solder and trim the 7 RECV diodes so that all seven anode wires are neatly connected to the RECV bus wire bridge installed in Step H41 H42e Solder all 7 RECV line diode cathodes on the solder 8 16 32 64128256 512 1K 2K 4K 8K side of the PC board Trim excess wires CATHODES DOWN FX 50 105 Stage H PROGRAMMING MATRIX ASSEMBLY Frequency N 2k 1k 512 256 128 64 32 16 8 4 There are two diode matrix programming areas on your PC board The 53 43 rd 10 686 1 o 0 1 1 O 1 1 1 obviously larger area is for frequency channel programming The second 53 45 H 10 690 1 0 space is for offset programming added in by U7 U10 53 47 E 10 6941 4 Correct assembly of the following section permits Q15 to switch off all three transmit offset programming lines while receiving allowing only the RECV eae ie OTO programming to be in effect Be certain to
123. rs to additional sections of U1 as a 455 KHz signal that needs demodulating a way of saying detecting analyzing decoding or just making something intelligent out of it all The MC13135 employs a conventional quadrature detector Inductor L1 is the quadrature coil requiring a simple one time adjustment The exact process of detecting intelligible FM voice or data from the 455 KHz 2nd IF is the job of the remaining sections of the MC13135 IC Because there s much more of this transceiver circuit to discuss and understand please study other sources if you are not clear on concepts such as Limiter FM Discriminator Quadrature phase shift and so forth As long as you just see the general flow of how a 52 525 MHz VHF FM signal can become intelligible audio input to the U2 speaker amplifier Stage B we re doing fine for now FX50 71 Stage CR Integrated FM RECEIVER with Squelch Control This step is named CR so that the assembly step numbers do not resemble designator numbers for capacitors To fully appreciate the marvel of U1 the MC13135 FM Receiver IC one would need to study the schematic diagram of any FM receiver more than 15 20 years old including fully solid state models The MC13135 IC is truly a Receiver on a Chip The cluster of parts to assemble and understand around U1 is minimal in comparison to what was previously required for a quality FM receiver circuit For years Ramsey Electronics has employed a simi
124. s Program as follows 1 Install diodes at the 8K and 2 positions 2 PLUS install diodes at 2K through 4 positions as needed per this Quick Reference Chart 3 For repeater channels add the RPT diode since 6 meter band repeaters are minus offset Simplex channels add the SIMP diode 4 A 1 means to install a diode 0 means NO diode Fag n ee ie sre se ea eee soi rosea oo to ToT ORE 53 05 a 10 610 53 07 ase 53 09 10 618 1 53 11 10 622 1 53 13 ae sr fos Te sa prose 7 sal 10888 7 0 0 0 53 25 a 10 650 0 1 1 53 27 10 654 0 0 0 0 0 0 4 O O Oj oj o i 0 0 0 0 0 0 0 0 53 29 asss 53 31 10 662 1 53 33 10 666 1 sa onj sa poor o OTTO sa o a eo ea pe 0 o O O OF Oj OF O Oj A AH mk O O oj O O O o OF o o O O O OF o O o OF oj OF ojl o _ oj O O O O OF OF CO OF O OF OF OF O OF gt AH O oj oj o O O FX 50 28 boob bbb bbe H22 40 a Install the 19 100K resistors brown black yellow required for R71 R89 Once again plan careful soldering procedure and install the NY ENNE H41 Form one diode matrix bridge for the RECV row of holes Using the heavier gauge bare wire in your kit shape insert and solder this wire bridge as illustrated H42a Select seven 7 diodes from the master supply of 1N914 or 1N4148 switching diodes p
125. s are exactly on the same frequency By tuning the one string to the exact pitch of the other you have corrected the phasing of the two independent frequency sources Pilots of multi engine planes or boats make slight RPM adjustments to get all engines in phase If you have two audio oscillators handy listen carefully as you adjust both to EXACTLY the same frequency Another analogy is the process of tuning a BFO equipped receiver to a perfect null or zero beat If you are exactly on frequency you hear nothing even though the BFO and incoming signal are both fully present In a PLL we want the beat note to be a perfect zero or constant direct current DC and this DC controls the VCO What breaks the circle What UN locks the loop the PLL Let s think and make a list of possibilities VCO will not tune in proper frequency range Bad Reference Oscillator IC crystal component Invalid N number A physical break in the loop Caused by what else Bad solder connections Incorrect components Defective components rare Incorrect programming The preceding is about as untechnical as we know how to get in giving a hint of how the PLL Frequency Synthesizer portion of your transceiver functions The Glossary of Terms in this book might give some additional help but there s really no substitute for just exploring the know how of modern communications technology by whatever learning method works best for you Now
126. s job the IC s 1st IF Mixer needs ANOTHER frequency source to mix with the signal presented by the antenna through the filters and preamps of Stage DR This other signal must be VERY precise since the mixer output is fed into a very sharp crystal filter at 21 40 MHz Specifically the 1st IF mixer seeks a second signal that is 52 525 21 40 31 125 MHz 3 Supplying the needed 31 125 MHz local oscillator input signal is the job of the tunable or programmable oscillator section of any receiver whether AM FM SSB HF or VHF etc In this case take it on faith that the VCO Stage F controlled by the PLL Frequency Synthesizer Stage H will deliver the precise 31 125 MHz local oscillator signal needed by U1 s 1st IF Mixer The VCO signal is applied to pin 2 4 No matter what we tuned in the 1st IF Mixer section of U1 delivers the incoming signal at 21 4 MHz to the next section of U1 This next section wants to do yet ANOTHER frequency conversion This is where we get the ideas of dual conversion and 2nd IF This time though no more variable input is expected beyond the FM IC s basic functions Crystal Y1 21 855 MHz completes another internal oscillator Its output is mixed with the steady 21 4 MHz signal from the 1st IF Mixer and we can start to see the whole picture 52 525 31 125 21 400 MHz 21 855 21 400 455 KHz 5 The 52 525 MHz signal at the antenna has gone through quite a sorting and converting process It now appea
127. se detector compares the signal from a reference oscillator to the signal from a programmable counter and sends a corrected control voltage to the LC section of a VCO Thus it can be considered a phase corrector See also VCO PLL VARACTOR PLATED THROUGH Refers to a style of PC board manufacturing in which traces on both sides of the board are interconnected by a coating of solder around the inside of each hole POLARITY Refers to the and sides of batteries power supplies power cables electrolytic capacitors etc PLL Phase Locked Loop a frequency generator circuit in which an oscillator output is analyzed by counters and a phase detector which controls and corrects the voltage supplied to varactor diode s which determine oscillator frequency POT jargon for potentiometer a variable resistor either a panel control or a mini device on a PC board PRESCALE Prescaler a circuit or device which divides an incoming frequency down to a lower frequency so that it can be handled more easily by later digital counting circuitry or devices PTT push to talk referring to all switches and circuitry involved in turning a transmitter on and off from a switch usually built into a microphone This switch may also be a relay or transistor in a packet TNC etc PUFF No not the magic dragon It s an easier way to say picofarads in the Ramsey warehouse and other high tech temples FX 50 42 soon as both string
128. set 270 201 Rub on project labels 2 99 2 sets 276 195 PC board standoffs 2 38 This 16 to 18 plus tax in basic hardware also presumes availability of all needed drill bits and or a reamer or punches of sufficient size to make the needed access holes for the rear panel jacks You ll also want to figure on spray paint as well as a clear finish to protect the panel labels Tools and supplies if not on hand could cost much more than the CFX enclosure kit itself In addition this style of case will have to be utilized upside down and also length wise rather than as designed This means that the top black becomes the foundation for mounting the PC board with the standoffs as well as securing the SO 239 antenna connector assembly You may wish to repaint the white bottom which now becomes the top And to use the project labels black lettering you ll probably wish to repaint both pieces This adaptation of standard Radio Shack hardware is adequate for indoor or occasional use but not recommended for mobile operation We are happy to provide this suggested alternative to the rugged case knob and hardware kit custom designed for the FXseries transceivers The choice is yours FX 50 11 THE RAMSEY CFX TRANSCEIVER ENCLOSURE KIT The CFX Kit is very obviously a fair value and solid investment for the long term performance and worth of your transceiver As we have mentioned we make it optional ONLY because some of our ham customers have
129. special Thank You for choosing this Ramsey VHF UHF transceiver as part of your ham radio beginnings We have tried to make this instruction manual as clear as possible However there are some VHF radio basics covered by the FCC question pools for all ham license study guides that we must presume that you have studied and understood Here is a simple guide to selected Technician Class questions to help with any review you wish to make before building FCC Subelement 3AA Selected Rules 4 2 11 1 1 12 5 15 2 FCC Subelement 3AB Operating Procedures 2 1 1 2 1 2 2 1 3 2 1 4 2 1 5 22 1 2 2 2 2 3 1 3 2 6 3 1 FCC Subelement 3AC Propagation It s up to you to understand the characteristic differences among HF shortwave VHF and UHF communications FCC Subelement 3AD Amateur Radio Practice All of this is fundamental know how for hams In working on this project be especially familiar with 1 1 1 1 1 2 1 1 3 7 1 9 1 through 9 5 dummy loads FCC Subelement 3AE Electrical Principles 3AF Circuit Components Please know ALL of this FCC Subelement 3AG Practical Circuits 4 21 FCC Subelement 3AH Signals and Emissions 1 1 2 1 1 2 4 1 2 6 2 2 7 1 4 1 6 1 2 7 1 1 7 2 1 7 2 2 FCC Subelement 3AI Antennas and Transmission Lines You will want to know all of this if you don t want to take all your savi ngs from building your own transceiver and spend it on a commercially built antenna Very good VHF antennas are easy and i
130. ted H44b Install 2 or more diode bridges in the channel rows of your choice H45 Install programming diodes for two or more channels per the following guide or per your own calculations or our Quick Reference FX 50 106 Using the FX series FM Transceiver Quick Reference Programming Guide In addition to pencil amp paper math calculation directions and also a handy computer BASIC program for programming the FX series Transceiver for any frequency and transmit offset within its specified range we provide this guide for binary programming of a variety of popular Repeater frequency pairs as well as some other frequencies of general interest All binary programming data for 2048 through 4 presumes prior diode programming of both the higher level binary inputs and the lower order binary inputs which remain constant for the 6 meter amateur radio band 32K 16K 8K 4K 2K through 4 on chart 2 1 0 0 1 0 see charts 1 0 You ll notice definite patterns in the standard repeater frequency assignments and their binary equivalents Look at these patterns up and down the programming input rows as well as across for any given frequency If your application could use more than the 12 channels easily programmed for front panel switching perhaps these patterns will give you some good ideas for additional channel switching convenience FX 50 27 FX 50 Quick Program Reference Standard 6 Meter band repeater pairs and selected frequencie
131. ter The PTT circuit may also be activated at pin 3 of the Packet I O jack A direct short to ground is not necessary The author noted very positive PTT action with resistance as high as 100K from pin 3 to ground This is a highly reliable and efficient PTT system provided that careful attention is given to correct selection and installation of all parts resistor values PNP transistors zener diode orientation U4 installation correct wiring of microphone jack Stage M ASSEMBLY PROCEDURE Install the following parts M1 C86 001 uf M2 C83 001 uf M3 C88 001 uf M4 C77 001 uf M5 C23 001 uf M6 R57 2 2K red red red M7 R59 100K brown black yellow M8 R58 270 ohms red violet brown Mga R50 10K brown black orange M9b R49 10K brown black orange M10 R51 47K yellow violet orange M11 R56 47K yellow violet orange M12 R61 2 2K red red red M13 R37 100K brown black yellow M14 C93 4 7 or 10 uf Watch polarity M15 C89 001 uf M16 C24 001 uf N RR OO BR Re RS OR i eh M17 Install U4 a 14 pin DIP IC type LM324 which contains all 4 op amp sections of this circuit Orient the notched end as shown on the board If you elect to provide a DIP socket use the same care as in soldering the IC itself FX 50 111 Stage M Microphone Amplifier and PTT Circuit If you have studied all preceding circuit explanations you have a good idea of what the Microphone and P
132. the diode matrix is predetermined to divide this frequency down to 5 KHz for phase comparison with the 5 KHz output of the crystal controlled reference divider Maximum N is 65 535 achieved by switching on all 16 parallel inputs Unlike simpler PLL IC s U6 s phase detector has TWO outputs at pins 7 and 8 These outputs go through very simple low pass filters R44 C68 R53 C91 to cut back the 5 KHz whine sound of U6 at work Op amp U5 A sums together the phase detector outputs and the output of U5 A is passed through a network of 2 2 uf electrolytic capacitors C67 70 90 92 to smooth out the phase detector pulses to clean DC for controlling the VCO R48 and C85 form yet another low pass filter to ensure that any 5 KHz FX 50 23 FREQ N BINARY PROGRAMMING VALUES Stage M Microphone Amplifier and Push to Talk Switching The lock detect output pin 28 gives a strong series of pulses when the PLL is unlocked When the PLL is locked only a tiny sawtooth wave appears at pin 28 The lock detect voltage is watched by U5 B If unlock pulses appear they are integrated through R90 and C96 as a fairly clean DC voltage charge built up in C96 If this charge causes U5B to swing low bias is removed from Transmit Buffer Q10 preventing transmitter damage and unwanted emissions 50 000 10 000 0010 0111 0001 0000 _ aa 2 33B a o Gls 54 000 10 800 0010 1010 0011 0000 Tegu f o aE whine will not get into the VCO Because the DC charg
133. tion amp Distribution Plus Packet Data I O Connector Stage B Receiver Audio Amplifier Stage CR Integrated Circuit FM Receiver Stage DR Receiver Tuned RF Input and Preamp Stage E F Transceiver VCO with Buffer Stages Each set of Assembly Instructions is introduced by an explanation of how that part of the circuit works and what it is for LEARN as you build ALSO INCLUDED IN THIS SECTION Master Kit Parts List Important Information About Kit Parts and the Printed Circuit Board TOOLS AND EQUIPMENT REQUIRED FOR CONSTRUCTION PLL SYNTHESIZER ALIGNMENT amp TRANSMITTER ADJUSTMENT Medium heat 25 to 50 watt soldering pencil with clean tinned tip Damp sponge to keep soldering tip clean Thin diameter ROSIN core solder Diagonal cutters or wire nippers Wire strippers Small pair of pliers Small screwdriver Ruler Tweezers to install SMT C75 Non metallic alignment tool Digital Voltmeter DVM 50 ohm Dummy Load 5 10 watt rating BS BE OR Re Be Re zs VHF RF power output meter ALIGNMENT A feature of the FX design is that Synthesizer Alignment can be accomplished by listening carefully to a transmitted signal of known accuracy To adjust trimmer capacitor C81 by the numbers use your Ramsey Frequency Counter or a digitally accurate VHF receiver with BFO FX50 51 FX 50 MASTER PARTS LIST Before beginning assembly take some time to check and organize these kit components in such a way that you can find them easily and
134. train relief grommet supplied with the transceiver kit in its rear panel hole Pass the black ground wire through this grommet The red fused wire will have to be unsoldered from S1 and then carefully FX 50 12 TRANSCEIVER PLL ALIGNMENT Our goal in this test is to verify soeech amplifier operation U4 actual FM modulation of a low level RF signal Q10 and correct operation of the PLL Frequency Synthesizer in Transmit mode If an antenna is connected for this test it will affect receiver operation only The antenna for the 10 milliwatt output consists of of the lead lengths and circuit board traces associated with C76 and C82 TEST PROCEDURE 1 Make sure work area is cleaned up and that the PC board is checked for wire scraps lodged between connections etc Set transceiver frequency to 52 525 MHz Simplex Obtain or make a non metallic alignment blade capable of turning the slug in L7 and also turning trimmer C81 4 Connect speaker microphone antenna and 12 15 volts DC Antenna will serve receive function only 5 Connect a digital voltmeter DVM of known accuracy to TP1 red lead to the test point and black lead to ground Set the meter to the lowest DC range that will handle up to 7 or 8 volts A digital voltmeter is used for this procedure because it has the required high input impedance 6 With the transceiver power turned on press the microphone button and adjust L7 for a reading of 1 6 VDC at TP1 7 A
135. transmit at 54 MHz it must tune to 54 MHz This indicates a tuning range of over 25 MHz What we have so far is a master oscillator for the transceiver that can be tuned by varying the voltage applied to the varactor diodes All we really need now is some precision way of controlling the voltage applied to those varactor diodes so that we can put that oscillator on any VHF channel we want with 5 KHz precision And this control obviously must be extremely stable since a change of only a few picofarads can tune through many MHz of VHF spectrum We know we can get stability by using a crystal oscillator but that would not allow us to operate on a multitude of channels without changing crystals for each channel How can we get such precision performance from small tuning diodes a very ordinary shielded coil and a transistor with its supporting capacitors and resistors We guess already that the answer must lie in the functions of the Frequency Synthesizer IC However the key to grasping what this IC really does lies in understanding TWO concepts frequency synthesis and the Phase Locked Loop or PLL The more of a handle that you can get on these two interconnected ideas the less mysterious your FX transceiver as well most other modern radio gear will be from ham transceivers to car stereos to cellular phones The VCO is an integral part of the phase locked loop You can read ahead about PLL and synthesis in the next section or you can proceed
136. uilt up in C96 If this charge causes U5B to swing low bias is removed from Transmit Buffer Q10 No damage is done and no offending signals can be emitted We ve toured The Loop Now let s build it and enjoy what it can do STAGE G PLL SYNTHESIZER CIRCUIT ASSEMBLY Since our most immediate goal is a functioning programmable receiver it is useful to know that the receiver portion could work fine WITHOUT the four binary adder IC s U7 U10 or the secondary diode programming matrix In practice this proposition need NOT be pursued because it would require 16 wire jumpers to connect the A inputs of the adders to the summing outputs Also the programming formula would involve addition of the receiver IF frequency For example to receive 52 525 MHz we would have to determine N as 52525 21400 5 Consequently we can see that it will actually be EASIER to install the 4 IC s install diodes in the RECEIVE line of the second matrix and proceed to find N simply by dividing our desired frequency by 5 KHz CONSTRUCTION PROCEDURE NOTE The suggested order of assembly for the PLL Frequency Synthesizer portion of your transceiver is exactly that a suggestion This stage involves some repetitive work that may seem extra easy but it also can become easier to FX50 93 The Phase Detector or phase corrector which compares the 5 KHz Reference Frequency with the intended 5 KHz output of the divide by N counter and sends correcting
137. uld be packed securely Insurance is recommended Please do not cause needless delays read all information carefully RAMSEY ELECTRONICS INC 793 Canning Parkway Victor New York 14564 Telephone 716 924 4560 Fax 716 924 4555 FX 50 50 Stage E BASIC VCO ASSEMBLY In this Stage we will assemble the basic VCO Voltage Controlled Oscillator circuit Understanding the function of this stage is especially important for knowing how the FX transceiver works 1 Install R26 100K ohms brown black yellow E2 Install Q5 2N3904 transistor observe correct placement of the flat side E3 Install R27 10K brown black orange E4 Install R15 1K brown black red E5 Install C36 01 marked 01 or 103 or 10 nf E6 Install PIN diode D1 BA482 small glass body marked BA482 Observe orientation of cathode band R A A OR E7 Install C99 01 uf a E8 Install C39 100 pf marked 100 or 101 E9 Install varactor diode D3 type FS4059 It has a small glass black body with a yellow band Be certain of correct diode identification and orientation of the banded cathode end E10 Install C40 47 uf electrolytic Watch correct polarity E11 Install R25 47K yellow violet orange E12 Install C104 01 uf disc capacitor marked 01 or 103 E13 Install C71 001 uf marked 001or 102 E14 Install R31 47K ohms yellow violet orange E15 Install R33 47K yellow violet orange RB BR R RR RR E16 I
138. unending and rapid circle of activity in which the VCO output is repeatedly affecting its own oscillating frequency self adjusting many times per second Hence an un ending circle or loop FX 50 89 Stage G The PLL Synthesizer Understanding and Assembly RAMSEY ELECTRONICS FX 50 1 96 REV 20 Tao we cont Z2 Weaker e A R7u C7 rate De v amp 121 Pi i FX 50 45 FX 50 88 PROGRAMMING BASICS SS Sees Sls Se asess Sh St SR Sree SS Ses SPS SE ees RAMSEY FX 50 VHF FM TRANSCEIVER KIT ASSEMBLY PHASE 2 Stage G Understanding and Building the PLL Frequency Synthesizer Stage H Building and Programming the Diode Matrixes Stage M Microphone Amplifier and PTT Circuit Stage TC Preparing Transmitter Coils RF Chokes Stage TO Other Transmitter Stage Preparation Stage TX Transmitter Buffer Driver and Final Each set of Assembly Instructions is introduced by an explanation of how that part of the circuit works and what it is for LEARN as you build ALSO INCLUDED IN THIS SECTION Detailed Explanation of PLL Frequency Synthesis How to Program the Synthesizer EASY PLL Alignment Directions Study the REFERENCE SECTION for additional help and tips on Frequency Programming Downloaded by RadioAmateur EU FX 50 87 4 Connect 12V DC speaker and antenna 2 of wire will do 5 With power on and volume at a low level s l o w l y tur
139. utput pin 7 requires filtering to provide good adjacent channel rejection A high performance 6 pole ceramic filter is used Filters such as this are used in virtually all FM radio transceivers Let s summarize the basic double conversion principle for receivers using the national 6 Meter band simplex channel 52 525 MHz as our working example 1 An antenna could be connected directly to pin 22 of U1 and our receiver on a chip would indeed work The antenna would bring in our theoretical test signal of 52 525 MHz as well as every other signal in the radio spectrum Since that s a bit much to expect the receiver to handle we will build up that network of filters tuned circuits and RF preamplifiers that constitutes Stage DR of this project The purpose of the DR circuitry is to filter out or at least diminish other signals while boosting signals in the 6 Meter region FX 50 70 up Secure VR1 to the board with the screw and nut After VR1 is mounted flat solder and nip the 3 leads A10 Study the PC board and locate the triangular set of 3 holes for VR2 type 7805 and insert VR2 so that the flat metal tab side is toward the center of the board Press VR2 in as far as it will go solder and trim A11 Near VR2 install C100 a 4 7 or 10 uf electrolytic oriented for correct polarity Stage A PROGRESS TEST The power input circuitry is completed and can be tested before proceeding Perform the test as follows g amp S
140. witch When 8 volts is applied through R107 and D22 to the base of Q6 the transistor collector grounds pin 1 of U2 thus silencing the receiver during transmit The COR output of U1 pin 16 also mutes the amplifier a feature which we ll discuss in the context of Stage CR Vee N C GND M C OUTPUT FX50 65 Stage B Receiver Audio Amplifier and Speaker Connection Stage B AUDIO AMPLIFIER CIRCUIT ASSEMBLY Some of the Stage A steps required more detailed explanation than simply inserting and soldering parts As we move along there will be more and more short one liners The following steps will complete a working audio amplifier ready to power up and test oS 9 B1 Install U2 the LM380 IC Be sure to orient the dotted or banded end as illustrated The use of a DIP socket for U2 is NOT recommended even if you use sockets for the other IC s Notice that most of U2 s pins are soldered to the PC board ground plane This provides heat sinking to the IC chip for proper heat dissipation AN paeen a e o e 6 o el NOOO a B2 Install C48 4 7 or 10 uf electrolytic observe correct polarity B3 Install C33 01 uf disc capacitor marked 01 or 103 B4 Install C41 1 uf disc capacitor marked 1 or 104 B5 Install R108 2 ohm red black gold B6 Install C34 470 uf electrolytic Watch out for correct polarity B7 Similarly install C29 330 uf electrolytic B8 Install C37 01 uf disc cap
141. with building and testing the VCO alone VCO CIRCUIT SUMMARY FX 50 81 Stages E F Transceiver VCO Voltage Controlled Oscillator and Buffer Stages OAG XAY ldy lA SAN ON1977F AIS WYN 280690000 wena eA gS Eo Jg O7 AAY 96 1 es x ara CCED VU n GS Opes FX 50 80 wAVIdS CRYSTALS 1 10 240 MHz has 2 leads Y2 PLL reference frequency 1 21 855 MHz has 2 leads Y1 receiver IF oscillator 1 21 4 MHz crystal filter has 3 leads FL1 1st IF filter INDUCTORS 1 455 KHz shielded inductor marked LB53303HK L1 2 7 5 turn 5 16 diameter to be wound in assembly L2 3 3 5 5 turn blue plastic adjustable coil L4 5 7 1 11 turn 228 diameter pre wound coil L6 4 2 2 uh molded RF choke green with red and gold color bands L8 11 17 22 2 8 turn 228 diameter pre wound coil L9 10 2 2 5 turn 5 16 dia to be wound in assembly L12 14 1 1 5 turn 5 16 dia to be wound in assembly L13 1 500 uH noise suppression choke large with black shrink tubing over the body L20 RRR RAAR SPECIALIZED COMPONENTS 1 Ramsey FX series main and low pass filter printed circuit boards 1 455 KHz ceramic filter molded cube 3 pins FL2 INTERNAL ALIGNMENT COMPONENTS 1 10K trimmer potentiometers marked 103 R46 2 60 pf trimmer capacitors C74 C75 1 35 pf trimmer capacitor black body orange top C81 FIXED VALUE CAPACITORS RF critical picofarad values
142. y illustrations to see whether the points in question are indeed to be tied together 3 Carefully check entire board for Loose bits of wire lodged among connections or components on either side of board 5 Excess wire lengths which may not have been nipped and are now bent flat probably against another connection BUILDING THE LOW PASS FILTER PC BOARD The assembly of the low pass filter PC board is quite different from the way in which you have assembled the main FX transceiver board Component parts are mounted on the circuit trace solder side of the board The reason for this is that the board mounts against the output connector and it would be very difficult to solder the connector center pin after the board is mounted to it You ll see why as you finish building your rig When installing parts insert the component on to the PC board from the solder side the leads will extend out through the bare side of the board with no traces The part is then soldered on the solder side and the leads trimmed away flush on the other side When soldering the disc caps be sure that their leads are properly soldered Sometimes the body insulating material will coat the lead preventing a good solder connection and you may wish to slightly scrape away this coating on some parts FX 50 122 Quantity RS Part No Description 1992 Price 1 270 272 74 Deluxe Project Enclosure 8 79 or 10 79 1 set 274 section Pkg of 3 or 4 knobs 2 00 3 00 1

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