please refer to his paper here
Contents
1. In researching the different ways I could create to lock my radio in this case an Icom IC 910 to a reference oscillator and maintain portability I stumbled across another ex telco rubidium reference call the FE 5680A originally used in Motorola cell sites What set this unit apart from all the others was that it would operate from 12v even though its specifications are 15 18v was tiny and it had a programmable output thereby simplifying the additional circuit requirements to attain the required operating frequency of the radio s oscillator A side benefit is that its cost is comparable with purchasing the ICOM CR293 high stability option currently 169 00 This Rubidium standard cost about the same including the box and circuits to complete the build Given the programmable nature of this unit it can easily be used to lock nearly any radio with a minimum additional circuitry and in some cases could be used directly David G4HUP has compiled a list of radios and their LO frequencies That list can be found here http g4hup com XCVR 20MO 2Dlist pdf FE 5680A s can be found on eBay from a few sellers at reasonable prices and others at not so reasonable prices so make sure you do a good search for them Some have an SMA for the 1OMHz output some have it on pin 7 of the D connector and some require modification to bring the RF out to the front panel In any case its straight forward to get the RF out of the unit Author Tim T2. are NPO ceramic C10 and C13 are Tantalum Electrolytics the schematic and parts list shows their value to be 10uF but I ended up using 47uF 16V units I scavenged from old PC cards C3 is a ceramic variable capacitor Don t use the tiny plastic things with cross head adjusters they are unstable as the temperature changes I only had SMD plastic units so I substituted a leaded unit with its leads folded back on themselves to enable it to be surface mounted Adjust C3 for maximum output L2 the 470uH inductor can be hard to source in 0805 size but can be found more readily in 1217 size Carefully removing the green coating from the traces to the pads will allow you to solder a 1217 size unit in place DS LED You don t need this for operation I just like to know when power is present in my circuits I used an 0805 sized green LED for mine You can use what ever colour you like provided you make the appropriate change to RS J1 and J2 are SMA connectors You could use SMB if you wanted too the pin pattern for SMA and SMB is the same regardless of orientation or whether its a vertical or right angle unit The 12V and GND pins were salvaged from old pc cards as was the connector Old PC sound cards have lots of these on them R2 and R4 are now 0 ohm rather than 100ohms This boosts the gain D1 thru D4 ensure you get BAT54 s not BATS4 AB or C s The ABC versions are dual diode packs and will not work in this circuit C14 is not re
3. that you can run an LED from so I added that to the front panel too These RB units run quite warm so a good metal box or aluminium panel is required to mount them You don t want to cool it to much you just want to add some thermal inertia to enhance its stability In hind site I should have mounted the BNC on the rear of the unit to make the cable run to the rig that much shorter and the shack table a little neater Author Tim Tuck VK2XTT QF56if BMARC WIA AMSAT VK AMSAT Version 1 24 Page 8 The labelling on the front panel I created with laser transfer film This product allows you to create water slide decal transfers that you can apply to nearly any surface Once the decal is attached to the aluminium panel you can bake the panel at 180deg C to fix the artwork permanently You ll notice a slight scratch on the bottom right corner This is the result of a slight tear in the film that I didn t notice until it came out of the oven Its brown tinge was cause by me using my pizza tray Make sure that if you follow this path to use a clean tray to put your panel on lest part of your dinner end up in the art work I could have used steel wool to remove the decal but I decide to leave the defect as a reminder not to do that again A7 ar us a Illustration 6 Fully assembled ready for operation You can power on the radio after you ve powered up the RB unit but it will take about 5 minutes for the lock light to
4. SES 2 2 EHI en etats en es case 13 Author Tim Tuck VK2XTT QF56if BMARC WIA AMSAT VK AMSAT Version 1 24 Page 1 An Easy Way to Lock your Radio to a Rubidium Reference For many of us playing around with microwave transverters the inherent stability and phase noise of our base radios leaves something to be desired Some manufacturers offer High Stability options for their radios but they still fall short of of the ultra stable and clean oscillators required for use at SHF frequencies Current Solutions GPS based 10MHz standards have become ubiquitous with many types available via eBay or other online sales mechanisms Most are ex Telco equipment and have excellent performance characteristics many of these have formed the basis of GPS locked oscillators for various radios The problem with most GPS based systems is that they re bulky and required voltages other than 12v to operate If you want to go mobile with your reference you have the additional problems of a second antenna to worry about and most GPS references require themselves to self survey once moved which means they wont have a disciplined output for 30 minutes or more Another option is to drive your oscillator with a 1OMHz rubidium standard which usually takes 5 minutes or less to produce a disciplined output but once again the more popular rubidium standards require 24v to operate making portable use harder than it should be An Easier Solution
5. Table of Contents An Easy Way to Lock your Radio to a Rubidium Reference 2 Current Solutions aa et St a sn aa nls ee 2 AM Easier SOLUTION pacts is TS PAR ed Sn te 2 Sp cification Compar son eek Abe el Gr detente tn tacle 4 Fig nng Out the FE 5680A nee unanime ae 4 Brostammmethe ER 3680A an aaa ae ee 5 Binldin ga Low Noise Topler asp nn Rte aah lou Ste tas 5 Add tionalAmplihieation sienne nent dans antennes 7 Completing the al sets Boia hee tn E AEE EA AREE EEEE E Rule 8 Mode the IE TUE RS fa EIER 10 Receiver Phase noise MOASUEMENIS LES ne Re er see 11 Conc IS TOT a aea an e a asa bes E E ated aaa A ara TE E na 11 Appendix A IC 910 Modification reproduced with permission of VK7MO 12 Appendix B Trippler sche MATE En AR A ce ns 13 Appendix C Construction Notes amp Fra une elle 14 Illustration Index Illustration 1 Typieal FE 5680A 2 002 eben 3 Hlustrallo 22 PrO O E S en ea ee see see 6 illustration 3 Assembled Tnplet u a see Re 6 Hlustration 4 MARS6 amplifier aueh ee ee Se pad 7 Illustration 5 interior with everything in place ea a Lit 8 Illustration 6 Fully assembled ready for operation 9 Illustration 7 Schematic Circuit Modification for the IC 910 10 Illustration 8 RX Phase noise at 1296 100 Mhz zen 11 Illustration 9 Modification of the IC 9T0 un 2a nk 12 Illustration 10 Trippler Schem tle SL a aD dE etat nt dns 13 lustration 1 12 Parts MI
6. excellent and more than enough for amateur radio applications Figuring out the FE 5680A While the RB is programmable for any frequency between 1Hz and 20MHz the factory builds a band pass filter for the resultant frequency prior to shipping Thus if you program a 10MHz unit to some other frequency there is significant reduction in the output of the unit so much so as to make it unusable My first idea was to reprogram the RB to 15 1MHz and simply double it to 30 2MHz to suite the IC 910 but the output was to far down to be usable My second idea was to program it to 10 06666666 MHz and tripple that to get close to 30 2MHz In this I was successful Author Tim Tuck VK2XTT QF56if BMARC WIA AMSAT VK AMSAT Version 1 24 Page 4 Programming the FE 5680A Data on programming the RB can be found here http www fetaudio com wp content uploads 2009 10 fei 5680A pinout jap pdf Alternatively a program has been written to reprogram the FE 5680 and that can be found here http www redrok com FE5680A zip Building a Low Noise Tripler Having looked at various tripler circuits on the internet I stumbled across an excellent article by Charles Wenzel of Wenzel Associates Inc titled New Topology Multiplier Generates Odd Harmonics The article can be found at this link http www wenzel com pdffiles1 pdfs RFDesign2 pdf This multiplier is also low noise and contributes little to the overall noise in the sy
7. go out and full stability to be reached Still much faster than a GPS unit and far more stable than the high stability options offered with these radios Initial testing of the unit involved running it for 72 hours continuously My HP5316B reference locked frequency counter has the ability to compare two signals and show any ratio difference between the two Thus I had my GPS reference locked signal generator plugged in to one channel and the RB unit plugged into the other Difference between the two signals was immeasurable over the test time Author Tim Tuck VK2XTT QF56if BMARC WIA AMSAT VK AMSAT Version 1 24 Page 9 Modifying the IC 910 Modifying the IC 910 is fairly straight forward so I modified my IC 910 in a similar fashion to how Rex VK7MO modified his There is a convenient plate covering a hole on the back of the IC 910 that I removed and drilled for the BNC Its only stuck on by glue so its easily removed and re glued in place This helps keep metal shavings out of the radio Schematic mods drawn by VK7MO are reproduced below Circuit Mods to IC 910 H Cut track for on off switch 650 Ohm Shielded lead BNC Socket Illustration 7 Schematic Circuit Modification for the IC 910 Pictures of the modifications to an IC 910 can be found in the Appendix A of this article Modification of other radios is left to the reader but a search of the internet will turn up many articles on modificatio
8. ious L amp C throughout the circuit Given that higher harmonics will be of much lower amplitude greater amplification will be necessary I intend to build a version of this for higher multiplication factors using a MAR6 s or BGA2709 s or similar and HSMS 2829 quad pack Schottky diodes for greater waveform symmetry and lower jitter Additional Amplification Now not required When I assembled the unit I didn t realise some my low value SMDs were the wrong value After building another of these units I found that the output came up to 10dBm which was more than enough to drive trhe IC 910 without the amplifier I ve since removed it Author Tim Tuck VK2XTT QF56if BMARC WIA AMSAT VK AMSAT Version 1 24 Page 7 Completing the Unit I built the unit into a nice box I found at http www rfsupplier com This box gives a tight RF shield and just enough heat sinking for the RB unit R8 R7 gt N OL x nr Im 1 Output R3 L10 Ci4 C9 3566 ae FE 5688A UN 3 TU Illustration 5 interior with everything in place As you can see from the picture I mounted the tripler on top of the RB unit with double sided tape and mounted the small amplifier using stiff wire directly to the back of the BNC connector I also placed a heavy duty diode on the DC input to avoid the inevitable reverse polarity incidents that always occur on field days and a fuse in the DC lead The RB unit has a lock indicator pin
9. n of the more popular radio s we use Testing of the IC 910 s frequency on 2m 70cm and 23cm show its output to be within 0 1 hertz of any selected frequency Author Tim Tuck VK2XTT QF56if BMARC WIA AMSAT VK AMSAT Version 1 24 Page 10 Receiver Phase noise measurements Phase noise tests using Spectrum Lab produced the graph below MEN Yeah I yi ya et I m Hlustration 8 RX Phase gt al 1 296 1 00 Mhz 5 Graph scale is from 1kHz to 1 160kHz with the Carrier at 1kHz and 0dBm as the left margin we can see the phase noise at 5hz is 65dBc Hz at 10 Hz its 72dBc Hz The spikes at 50hz 100Hz and 150Hz are hum from the linear supply used to power the rubidium unit thus illustrating the need for a clean supply for local oscillators Conclusion The power supply must be clean to minimise spurs which is not a problem if using a battery Accuracy is better than 0 1Hz and is highly stable Specifications are comparable to GPS locking methods Reference locking your radio is easier than you think and can be cheaper than buying the High Stability option for the radio Author Tim Tuck VK2XTT QF56if BMARC WIA AMSAT VK AMSAT Version 1 24 Page 11 Appendix A IC 910 Modification reproduced with permission of VK7MO Leads to switch back DC to Internal Oscillator a BNC le 30 2 MHz Cut track with DC to Internal Osc eS 680 Ohm resis
10. quired and is an error in the circuit Ether replace it with a 0 ohm resistor or jumper it with solder R7 8 amp 9 form a 50ohm 3db pad that you can modify for extra attenuation if the output is too high for your application Author Tim Tuck VK2XTT QF56if BMARC WIA AMSAT VK AMSAT Version 1 24 Page 14
11. stem Using this circuit I added an additional 7 pole chebyshev low pass filter and amplifier stage to reduce any residual harmonics and amplify the signal to a suitable level I also added an LED to show when power is applied I ve used PCB mounted SMA connectors for the RF and the board is designed so that the SMA s can be mounted from either side of the PCB The complete circuit is reproduced in Appendix B Author Tim Tuck VK2XTT QF56if BMARC WIA AMSAT VK AMSAT Version 1 24 Page 5 I first built the circuit using standard components to test the design Illustration 2 Prototypes The images show the tripler on the left and the filter amp on the right While these worked ok I wanted to do this in SMD and on a single double sided PCB Using the PCB CAD software DipTrace I created a PCB pattern for SMD components This PCB I then had manufactured by one of the many Chinese FAB plants for a reasonable price Assembly of the SMD board took about an hour and worked first go Testing the output of the RB tripler circuit produced an output within a few millihertz of 30 2MHz Success oe TO af kei ay Output R3 LC C14 C9 ea ao Illustration 3 Assembled Tripler Author Tim Tuck VK2XTT QF56if BMARC WIA AMSAT VK AMSAT Version 1 24 Page 6 While I ve called this a tripler the circuit is quite capable of being used for other odd harmonics with appropriate changes to var
12. tor Internal supplies 30 2 MHz External to junction of R515 and C515 Osc Switch Shielded Lead for 30 2 MHz Illustration 9 Modification of the IC 910 Author Tim Tuck VK2XTT QF56if BMARC WIA AMSAT VK AMSAT Version 1 24 Page 12 Appendix B Trippler schematic 10 0666667 Mhz in 2 2uH La B 47OuH c3 5 0 77 BZN 0 30pF 5 t AC 220pF D2 Mt D 1 pF L3 NL252 18T R22J 30 2 Mhz out Illustration 10 Trippler Schematic RefDes Value Type C1 220pF CAP_0805 L1 1uH IND_0805 C10 10uF CAP_1210 L10 100uUH IND_0805 C11 0 1uF CAP 0805 L11 2 2uH IND_0805 C12 15pF CAP_0805 L2 470uH IND 0805 C13 10uF CAP_1210 L3 0 22UH IND_0805 C14 15pF CAP_0805 L4 2 2UH IND_ 0805 C2 100pF CAP_0805 L5 100uH IND_0805 C3 0 30pF VARCAP L6 2 2UH IND_ 0805 C4 n r CAP_0805 L7 330nH IND_0805 C5 15pF CAP 0805 L8 330nH IND_0805 C6 150pF CAP_0805 L9 330nH IND_0805 C7 220pF CAP_0805 Q1 J310 PMBFJ310 C8 220pF CAP_0805 Q2 J310 PMBFJ310 C9 150pF CAP_0805 R1 100 RES_0805 D1 BAT54 R2 0 RES_0805 D2 BAT54 R3 100 RES_0805 D3 BAT54 R4 0 RES_0805 D4 BAT54 R5 680 RES_0805 D5 LED RG 39 RES_0805 J1 COAX R7 150 RES_0805 J2 COAX R8 150 RES_0805 Illustration 11 Parts List Author Tim Tuck VK2XTT QF56if BMARC WIA AMSAT VK AMSAT Version 1 24 Page 13 Appendix C Construction Notes amp Errata All capacitors except C10 and C13
13. uck VK2XTT QF56if BMARC WIA AMSAT VK AMSAT Version 1 24 Page 2 More detail on the FE 5680A can be found here http www fregelec com rb_osc_fe5680a html Illustration 1 Typical FE 5680A Author Tim Tuck VK2XTT QF56if BMARC WIA AMSAT VK AMSAT Version 1 24 Page 3 Specification Comparison The specifications of the FE 5680 are comparable to the popular GPS reference the Trimble Thunderbolt as this table of the main parameters show Parameter FE 5680A Trimble Thunderbolt Frequency 10MHz 10MHz Type Sinusoidal Sinusoidal Amplitude 7dBm 12 5dBm Harmonic Level 30 dBc 40 dBc Spurious 60 dBc 70 dBc Phase Noise 10Hz 100 dBc Hz 120 dBc Hz 100Hz 125 dBc Hz 135 dBc Hz 1000Hz 145 dBc Hz 135 dBc Hz 10MHz Accuracy 2x 10 day 1 16 x 10 day DC Requirements 12V to 18V 12V 12V 5V Input power 11 watts steady 27 watts peak 10 watts steady 15 watts peak Size 25 x 88 x 125 mm 51 x 102 x 127 mm It is expected that the accuracy of the Trimble to be higher than the RB unit since its constantly comparing and updating against the standards orbiting above Also the phase noise of the FE5680 is slightly worse due to its output being that of a DDS rather than directly from a VCXO The FE5680 does contain a VCXO but that is part of the loop in front of the DDS That being said the specifications of both units are
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