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ZL1BPU LF Exciter User Manual

1. Fig 6 1 Select the device Press OK and then on the Manager tab of the next screen give the project a title and then from the main program menu select Project Save Project to save the project file The next step is to check for communications with the micro Select Options Change Printer Port and you should see a Port available message If all is well select CANCEL If not try changing the port in case it isn t LPT1 Next select Program Read EEPROM which should be something safe to do it won t matter what you do if the micro is already blank If all is well the data from the micro will fill the Data EEPROM Memory window EEPROM Data Memory iol x Fig 6 2 The Data EEPROM Memory window You can see this window by clicking on it or the menu Window EEPROM Data Memory User Manual Page 29 If the cable is faulty or not connected you are likely to see an error message like Dongle Check gt STK200 STK300 or Value Added Pack Dongle Required Fig 6 3 Oh dear no faulty programming cable the cable is connected but there is a fault at the Exciter perhaps the programming header is wired incorrectly is plugged in backwards or there is no power applied to the Exciter you will see a different message Hardware Check N 479052313 Part Not Detected This may be due to power off on programming module Security Bits Enabled or a pre production AVR Fig 6 4 No comm
2. command which sets the keying rate are always expressed as four characters So we send the command K00CO Argo beta 1 build 123 File Setup Mode Speed Capture About 753317 PM Peak at 1043 41 0 336 Hz ORSS Viewer p 3s dots normal Estim Magnitude __ Full Band View Hz 1130 1120 1110 1090 1080 1070 1060 1050 1040 ABC I 1102 96 2 oN Sensitivity Contrast Ticks 10 seconds Stop Fig 3 1 QRSS with 3 second dots Another example to generate accurate JASON symbols 11 8 sec per element use a timer value of 11 8 x 64 755 KO2F3 If your symbol clock is slightly off 64 Hz you can easily tweak the value since the timer has plenty of resolution For Morse code at normal speeds we first need to work out the dot speed The usual value for Morse dot speed is 1 2 x the speed in WPM For example for 12 WPM that s 12 x 1 2 14 4 Hz There are two clocks per dot element one for the dot and one for the space so we need to double the normal value used for Morse speed so for 12 WPM we need a clock rate of 14 4 x 2 28 8 Hz The nearest we can get to 28 8 Hz is 32 Hz divide by 2 or a setting of K0001 since the timer counts from zero and the resulting speed will be 32 2 4 13 3 WPM User Manual Page 15 The Power Amplifier Good news no mathematics here The power amplifier uses a Philips TV audio amplifier which has two
3. The eight square wave CMOS 5V level outputs have sub microsecond rise times It is also possible to use two 4 bit sine cosine tables to generate two signals with constant and accurate 90 phase relationship This is useful with quadrature modulators or demodulators e g using the phasing technique Output Ports Three digital outputs can be controlled for external use controlled via script or serial command Power Supply 12V DC to 15V DC at about 300mA Supply need not be regulated Key up 10mA key down up to 150mA Will operate at reduced output down to 7V No standby power required for memory retention Commands Twelve immediate mode user commands Six script commands Scripts are downloadable and used for beacon messages Serial Interface RS232 TXD and RXD only at up to 19200 bps user selected no parity eight bit data one stop bit The synthesizer stops while processing commands Data rate is stored in EEPROM there is only one version of the firmware Beacon Messages 112 bytes of user EEPROM message memory containing coded data and commands Memory is sufficient for about 15 words in Morse 8 in JASON or three words in S MT Hell or Feld Hell 16 bytes of EEPROM are used to store the current user settings for power up beacon or normal mode restoration Physical Can be built on a prototype board about 100 x 75mm and will fit in a TNC sized box The Exciter will operate from 0 to 70 and will tolerate thermal a
4. and changes of carrier frequency FSK shift and baud rate keying speed You can even set outputs for controlling external equipment These commands always start with a hexadecimal F The beacon commands are listed in the Appendix Note that they are NOT the same as the KISS protocol commands used to control the unit via the serial port although similar in effect The compiler provided by the author MAKEBCN EXE can compile only Morse messages and embedded commands MAKEBCN is very handy because as well as generating the beacon message it downloads it to the Exciter making the process really easy If you wish to add other modes to the message you will need to work out the complete message on paper first and laboriously enter it with the B command Argo beta 1 build 123 x File Setup Mode Speed Capture About 6 36 49 PM Peak at 1083 85 0 084 Hz GRSS Viewer m 105 dots normal Estim Magnitude Full Band View Hz Contrast Reuse se ca Fig 5 2 An ARGO picture of the LF Exciter sending MT Hell User Manual Page 26 Controlling the Outside World There are three controllable outputs PD2 PD3 and PD4 These can be controlled by direct serial command the P or PORT command or from the beacon script This latter feature is really valuable because it allows you to operate at different power levels on different antennas or even on different frequenci
5. the value for 9600 bps using a 12 8 MHz crystal is 12800000 9600 x 16 1 82 33310 Choose the nearest integer value 8210 or 52 check the speed error recalculate back the other way using the following formula UART Speed 16 x UART Divider 1 5 Using the value 82 this gives a speed of 9638 5 bps about 0 4 in error Any error less than 0 596 is acceptable If the error is higher use a lower communications speed or change the crystal Beacon Message The beacon messages are stored in compiled form in other words in a form easily understood by the micro controller There are several different formats used e Morse in Murphy format for ASK QRSS FSK and DFSK Morse e Bit maps eight bits high for Feld Hell and MT Hell modes e JASON format frequency offset for JASON IFK e special embedded command format The format for Morse is the widely used Murphy format where dots are represented by 0 dashes by 1 and a 1 follows the last element Inter element and inter character spaces are generated automatically A complete list of Morse characters in this format is given in the Appendix One character is sent per byte and the format applies to all Morse related modes ASK FSK and DFSK There are two graphics modes Feld Hell amplitude vs time and MT Hell Frequency vs time The same Hell graphics font can be used for both modes but they way the characters
6. while if the bit is 0 silence is transmitted for the duration of one full dot This mode is completely compatible with slow Hellschreiber DX Mode can be achieved by storing each column of data in the script two or more times MFSK IFK BEACON The Exciter transmits MFSK multi frequency or IFK incremental FSK keying using data The message sent is contained in the beacon script and must be coded using the required data format For example IFK encoded using the JASON technique Each script byte represents one transmitted symbol and the data is sent as an offset frequency from the nominal carrier frequency set by the F command Appropriate values are from 0x00 to OxEF and operate in resolution steps Symbols are transmitted at increasing frequency similar to setting an offset with the A command or decreasing frequency if the carrier frequency is negative Each of the modes interpret the script data in a different way so make sure you select the correct mode for the beacon data or rubbish may result The best way to achieve this is to include the appropriate mode command in the message 13 Therefore for JASON there should be three resolution steps per JASON IFK step If JASON is operated correctly in serial port mode with the ZL1BPU protocol enabled the IFK commands will be multiplied by three in the PC software and the Exciter will send perfect JASON If these commands are captured they can be loaded int
7. 13 12 11 16 OC 01 ZL1BPU User Manual Page 64 Fl FE 00 CO 3 sec dot ASK mode QRSS 01 11 16 OC BPU F2 FD 40 3 sec dot FSK Morse 01 11 16 0 BPU F3 FD 40 DFSK mode 01 13 12 11 16 0 ZL1BPU F6 FE 02 FO JASON mode 11 8 baud 00 1B 1E 1B 24 1B 2A 18 ZL1BPU BCN RF72KU 1E 12 1B 15 18 12 24 OC OF 03 OC 00 OC 03 18 00 03 00 0C 06 OF 03 18 06 0C 15 OC 18 12 24 21 FC 20 A6 00 Change frequency slightly FA FE 00 10 FD 18 MFSK image mode MT Hell 3 sec 01 41 45 49 51 41 00 2 01 01 L 20 7F 00 1 49 49 36 00 48 48 30 00 01 01 7E 00 U F5 FE 00 03 Feld Hell mode 1 sec columns 01 41 45 49 51 41 00 Z 01 01 L 20 7F 00 1 49 49 36 00 48 48 30 00 01 01 7E 00 U FF FF End of message User Manual Page 65 Morse Coding Using Murphy coding each dot is represented by 0 and each dash by 1 packed right to left in a single byte A 1 is placed in the next free bit to the left to signify end of character and remaining bits to the left remain 0 As each element of the character is transmitted the data byte is shifted right and the carry transmitted and followed by inter element spaces until the remaining data is 0x01 i e 00000001 Coding is arranged so that automatic inter character spaces are correct at three dot lengths and since space is coded as no data elements but followed
8. 2 x WPM 7 This formula is not the same as the normal formula used for Morse speed 2 4 x dot speed because there are two symbol events per dot element the dot and following space So for the Exciter sending Morse you can use the following formula KEY 53 3 WPM 8 For QRSS use this formula KEY 53 3 x QRSS secs 9 Of course you then have to convert the value to hexadecimal to send it to the Exciter Here are some typical settings Morse 12 WPM K0004 Morse 5 WPM K000B QRSS3 KOOCO QRSS10 K0215 QRSS120 K1900 Table 7 1 Speed settings In Sweep Generator mode K sets the frequency increment per step The units are resolution steps as for the command but range is limited to from K0000 to KFFFF over 5 kHz step It may not seem logical to use this command for the frequency step size but the most obvious command to use A has only 8 bit resolution offering only 0 255 resolution steps 21 Hz This would have seriously limited the usefulness of the sweeper In effect the functions of these two commands have been swapped in Sweep Generator mode in order to improve the step resolution Sweep dwell time does not need high resolution User Manual Page 35 MODE Syntax Mn This command tells the Exciter to change beacon MODE If the mode is zero the beacon is turned off otherwise the beacon is turned on in one of the six operating modes The modes are MO M1 M2 M3 M4 BEACO
9. If communications are lost the program reports an error at the bottom of the screen All these messages are periodically erased every 10 seconds to keep the screen tidy The Connect to Com message at the top right corner of the screen reminds you which port the software is expecting to see the Exciter on This and the serial communications data rate are read from the setup file EXC SET This program does not at present allow bit map files for MFSK MT Hell and Feld Hell modes M4 and M5 be compiled and downloaded You will have to make them manually and laboriously or use EXC EXE to create them in a manner similar to that described for JASON Source code for the MAKEBON program is available from the author The price includes email support 16 Email zl1bpu nzart org nz User Manual Page 56 This DOS program has many similarities to MAKEBCN but is intended for real time control in other words as well as the program controlling the transmitter when you type into the program it sends what you type EXC provides 1 Real time control of the transmitter turning it on off and sending text from the keyboard in any pre defined mode 2 Sends a choice of pre defined messages from file 3 Sets keying parameters speed shift modulation technique according to the selected mode These modes are also pre defined in a file WinEXC by Con ZL2AFP is essentially a Windows implementation with the same func
10. MODE and KEY Sweep mode settings are not saved T TX T turns the transmitter on Wmm WIDTH Sets number of sweep steps where mm is 00 to FF in two hexadecimal characters Typical value is W14 for 20 steps 50 baud 170 shift RTTY with 2125 Hz MARK can be simulated with W02 AF8 7 5 F0062B1 The start frequency for the sweep is set by the F command sweep dwell time by the A command and the sweep step size by the command WOO turns off the sweep X RX X turns the transmitter off User Manual Page 63 Beacon script Commands F1 Mode 1 ASK Morse F2 Mode 2 FSK Morse F3 Mode 3 DFSK Morse F4 Mode 4 MFSK Graphics Sequential MT Hell F5 Mode 5 ASK Graphics Feld Hell 6 Mode 6 Data Jason FB pp Set port pins see the P command FC hhmmll Set frequency see the F command FD nn Set FSK shift or MFSK increment see the A command FE nn nn Set keying speed baud rate see the K command FF End of script The FB FC FD and FE commands are functional replicas of the corresponding KISS commands Script Examples If you load all this data in using the B command the beacon will send everything one mode after another The complete message will not of course all fit in the 112 byte memory so just use the bits you want to try out and place at the end FC 20 A6 E9 Set operating frequency 181 4 kHz using a 12 8 MHz crystal F1 FE 00 04 10 wpm ASK mode Morse 01 09 02 01 DE 01
11. The region between 30 kHz and 300 kHz Least Significant Bit In a byte or word of data the bit with the lowest weighting the right most bit Multiple Frequency Shift Keying A method of coding data as different usually sequentially transmitted frequencies to represent more than one bit of data per event FSK is simply two frequency MFSK with one bit per event An image mode where text is sent as dots Each column is scanned bottom to top left to right Each row of dots is sent on a different slightly higher frequency and non visible dots are not transmitted The mode is extremely immune to noise and ionospheric effects since the data is received using an FFT technique such as ARGO and interpreted by eye There are two types concurrent and sequential This Exciter sends the sequential one dot at a time version which does not require a linear transmitter See Feld Hell Phase locked loop A type of frequency synthesizer Phase Shift Keying Data is encoded as shifts of carrier phase Slow ASK Morse QRS means please send slower Very slow ASK Morse Program which in this context operates in a general purpose computer where the program can be loaded or changed at will Human readable program instructions which are also readable by a program compiler or interpreter which converts the program into native micro controller or computer instructions The smallest data entity of a digital transmission A symbol ma
12. content of pp The format is the same as the KISS PORT command i e only the three least significant bits are useful and they control the same outputs FREQ Syntax FC hh mm Il Sets the frequency to hhmmllugx resolution steps above zero in other words the format range and resolution are the same as the FREQUENCY command This command allows you to QSY in the middle of a message for example to create a dual frequency beacon or to reverse the direction of keying shift by switching to negative frequency SHIFT Syntax FD nn Sets the carrier frequency offset to nn resolution steps This command works in the same way as the KISS ADD command i e the offsets are based on the nominal carrier frequency and do not accumulate as additional shifts are processed This command has no effect on modes 1 5 and 6 A shift of 1 Hz is achieved with FD 0 User Manual Page 42 SPEED Syntax FE nn nn Sets the beacon keying speed i e the speed at which symbols are transmitted The value of nnnn can be from 0000 to FFFF The baud rate is 64 nnnn and the definition and use is exactly the same as the KISS KEY command END Syntax FF Marks the end of the beacon script The next data processed will be at the start of the script Message Recording Recording a beacon script message is simplicity itself However as you will have discovered from the command list and the fact that the message is pre coded generating the message isn t
13. different crystal frequency or are using 12 7 12 8 MHz but don t want to load the demonstration message The EEPROM Data Memory window will probably show all values as FF so leave them as they are it won t matter what they contain If the EEPROM in the device is blank reading it will restore all values in the window to FF Next count along to the 8 byte in the first row and change it to your required data rate see Crystal frequency in Chapter 5 The example below shows setting to 9600 bps with a 12 8 MHz crystal EEPROM Data Memory Fig 6 5 Patching the Serial Comms data rate Then program the EEPROM as described above If the message on the Terminal is still garbled check your maths again and check the Terminal data rate Table 6 1 gives the value to load for a range of common crystals and communication speeds of 9600 and 19200 bps Where no value is given for 19200 bps the error would be too great for reliable communication gt 0 5 Crystal MHz 9600 bps 19200 bps 9 437184 Ox3D E 10 000 0x40 12 000 0 40 0 26 12 700 0 52 12 800 0x52 15 0994944 0 62 0x30 Table 6 1 Typical data rate values User Manual Page 31 7 So now you should have a working Exciter Check that the serial communications work both ways by typing H on the Terminal keyboard you should see a list of commands and the unit w
14. local manual control with the beacon switched off F1 ASK Sends on off keyed Morse from the in built beacon message The message is stored inside the Exciter memory as Morse characters F2 FSK Sends frequency shift keyed Morse The key up periods are sent at the set frequency set by the FREQ command and the dots and dashes are sent at a higher frequency raised by the amount set by the SHIFT command F3 DFSK Sends dual frequency keyed Morse Dots are sent at the set frequency while dashes are sent at the offset frequency defined by the SHIFT command Importantly the dashes are the same length dots and spaces between elements are omitted if the elements are different making them unnecessary This mode is easy to read visually and is much faster than ASK or FSK Morse F4 MFSK A bit mapped mode Sends each bit of each data byte in the message at a different frequency If the bit is one the carrier is on if zero it is off The SHIFT command sets the difference between the frequencies The lowest significant bit is on the nominal set frequency and is sent first Subsequent bits are raised further in frequency by the SHIFT even if not transmitted Zero not transmitted dots have shorter duration than one transmitted dots You could capture the output of this mode to create an MT Hell beacon message F5 HELL A bit mapped mode Can share the same font information as MFSK but can benefit from specially designed c
15. or down if the carrier frequency is negative In this mode intra character gaps are omitted if the following element is different and all elements are of dot length MFSK BEACON The Exciter transmits MFSK multi frequency keying using graphics This is in effect a Sequential Multi tone Hellschreiber mode The message sent is contained in the beacon script and must be coded using a graphics image or text in graphics format A suitable font is included in the Appendix Each script byte represents one column of User Manual Page 36 5 M6 graphical data and the data is sent LSB first representing the lowest frequency dot set by the command If any bit is 1 it is transmitted with full dot duration set by the command while if the bit is 0 silence is transmitted for the duration of one half dot Bits following the LSB are transmitted at increasing frequency step size set by the A command or decreasing frequency if the carrier frequency is negative HELL BEACON The Exciter transmits ASK keying using graphics The message sent is contained in the beacon script and must be coded using a graphics image or text in graphics format A suitable font is included in the Appendix Each script byte represents one column of graphical data and the data is sent LSB first All dots are sent at the same frequency set by the command If any bit is 1 it is transmitted with full dot duration set by the command
16. reading Don t tweak the value in the file again Note in all cases measure the Exciter output not the crystal frequency Measuring the crystal frequency will cause the oscillator to shift and maybe even stop oscillating User Manual Page 48 Remote Control None of the software described below suits remote operation of the ZL1BPU LF Exciter However you can operate the Exciter remote using KISS commands either via a modem or via a Packet Radio TNC in connected or unconnected mode Connected would be best as that spares the Exciter from receiving unnecessary and confusing data Turn off all TNC reporting and unconnected messages With the exception of message programming the B command all commands will operate with a 9600 bps link to the TNC In order to use remote reprogramming you should use a 300 bps link to the TNC and preferably keep the message size down to one packet s worth The Exciter can be controlled remotely quite satisfactorily with a conventional packet radio program and it will also send back the normal KISS mode responses You may need to be patient if the channel is busy probably best to use a little used channel Real time keying operation above QRSS60 would not be practical since timing accuracy is lost over a packet radio link MAKEBCN This DOS program has three main functions 1 Real time control of the transmitter turning it on off and sending a basic Morse ID message This al
17. special features full power output to at least 250kHz and a DC volume control with a very wide range This design uses both of these features See Fig 4 4 Input to the power amplifier essentially a linear amplifier is AC coupled from the digital to analog converter D A output sine wave and attenuated to the correct input level about 1V p p The transmitter is keyed on and off not by keying the amplifier but by stopping the DDS generator so the D A output simply stops changing phase while the transmitter is off This prevents thump which is caused by DC shifts Keying transients are generated when using on off keying of course but have not been a problem There are no transients when using FSK keying as the Exciter generates phase continuous signals on frequency change The amplifier chip is designed to drive a balanced loudspeaker load so for RF use a balanced broadband transformer is used Since the transformer DC resistance is very low a blocking capacitor prevents DC imbalance in the push pull output stage The output has taps to allow it to drive loads from 50 Ohm down to fractions of an Ohm All you need do is select the tap that gives the best output power The chip is reasonably indestructible and will shut down if overloaded Experience has shown however that it does not like having high power from another transmitter pumped into its output The DC volume control input connects to the front panel power level pote
18. too large Next the message will be slowly sent to the Exciter and when it has been stored the command will be terminated and the Exciter will revert to what it was doing before The Exciter stores Morse very efficiently one byte per character so quite large messages can be sent In addition all the other direct commands can be embedded in the script message and will be converted into beacon message commands You can therefore change mode change shift which is necessary when you change FSK speed or use MFSK for example change keying speed User Manual Page 54 and even frequency so you can for example set up a dual frequency beacon Text to be converted to Morse is simply typed into the file use spaces for pauses Both upper and lower case are recognised all punctuation and some symbols and prosigns are included The commands are included in the script using the exact same syntax as the Exciter commands except they are prefaced with a character SHIFT Ann 0 255 resolution steps about 0 25 Hz Value in HEX 00 FF FREQUENCY Fhhmmll 0 2 resolution steps value in HEX 000000 400000 Use the F6 key to find out what the current settings are KEYING SPEED Knnnn 0 65536 dot clocks per dot period See the F8 key above for more information The value is in HEX 0000 FFFF MODE Mn Sets beacon keying mode M1 to M5 is not a valid script option is not supported A tilde character is u
19. 0mA For recording the beacon message and setting up a dumb terminal or PC terminal capable of 9600 bps N 8 1 Programming To program the micro controller in the unit you need the following only once during the construction and commissioning process e An AVR programmer simple parallel programmer is recommended Use the ATMEL ISP programming software e EXCITER firmware available from the author e APCrunning Windows 3 1 95 or 98 to run the programming software Real Time Operation In order to use the ZL1BPU LF Exciter for real time QSOs you will need a PC or other computer with relevant software You could write your own or use one of the DOS or Windows applications provided by the author These are freely available from the website The author s software provides Morse QRSS DFSK and MT Hell keyboard operation You will need to use other software for reception The author s software is intended for use in conjunction with ARGO by See www qsl net zl1bpu micro or http sharon esrac ele tue nl mirrors zl1bpu micro for a suitable programmer Alternatively have a friend program the device for OU oo Where to get the Software at the bottom of the General Information page www weaksignals com User Manual Page 4 I2PHD and IK2CZL In order to write your own software you will need to understand the KISS commands which are listed under Serial Commands in the Appendix Building t
20. 5 1F 15 02 4 1E 02 07 02 00 96 19 1A 04 0B 13 5 10 15 15 15 02 amp 0A 15 0D 02 05 6 0E 15 15 15 02 00 10 18 00 00 7 10 10 17 18 00 00 0E 11 00 00 8 0A 15 15 15 0A 00 11 0E 00 00 9 08 15 15 15 0E E 15 0E 1F 0E 15 00 05 05 00 00 04 04 1F 04 04 00 0A 0B 00 00 00 01 06 00 00 04 0A 11 00 00 04 04 04 04 04 00 0A 0A 0A 00 00 03 03 00 00 gt 00 11 0 04 00 01 02 04 08 10 08 10 15 14 08 0 11 15 15 08 1F 14 14 14 08 A 0F 14 14 14 0F Q 1F 11 15 13 0F B 1F 15 15 15 0A R 1F 14 16 15 09 C 0E 11 11 11 00 08 15 15 15 02 D 1F 11 11 11 0E 10 10 1F 10 10 E 1F 15 15 15 11 U 1F 01 01 01 1F F 1F 14 14 14 10 V 18 06 01 06 18 G 06 11 11 13 0 W 16 01 06 01 1 H 1F 04 04 04 1F X 11 0A 04 0A 11 00 11 1F 11 00 Y 10 08 07 08 10 J 02 11 1F 10 00 Z 11 13 15 19 11 K 1F 04 0A 11 00 1F 11 11 00 00 L 1F 01 01 01 00 10 08 04 02 01 M 1F 08 04 08 1F 11 11 1F 00 00 N 1F 08 04 02 1F 00 08 10 08 00 1F 11 11 11 1F _ 01 01 01 01 01 User Manual Table 9 2 The Hell Font table EEPROM Memory Locations Most of the EEPROM memory is dedicated to the beacon message Using the table below it would be possible to program beacon messages via the programming software which might be easier if the message was complex There are also a few interesting locations before the message Addresses and contents are given in HEX Address Default Content 0000 00 0001 00 0002 20 High byte of default op
21. FIER c12 TDA7052A ry eee OUTPUT O47uF 50 50 Ohm output tap down forlowZ antenna OUT 5 4 VC OUT 8 SIG GND PWR GND 3 L1 20207 Core TN25 15 or similar POWER AMPLIFIER Copyright 2002 Murray Greenman ZL1BPU User Manual Page 73
22. N OFF In this mode the Exciter is a CW generator that can be controlled in frequency by the A and F commands on and off by the T and X commands and into Sweep Generator mode with the W command ASK BEACON The Exciter transmits ASK on off keying using Morse The message sent is contained in the beacon script which can also modify the behaviour and even the mode of the beacon In ASK mode the keying speed is controlled by the K command This mode uses the Murphy interpreter to convert script data to Morse FSK BEACON The Exciter transmits FSK frequency shift keying using Morse The message sent is contained in the beacon script which can also modify the behaviour and even the mode of the beacon In FSK mode the keying speed is controlled by the K command As with other FSK modes the F command sets the idle frequency while the A command sets the key down FSK shift The key down shift is up in frequency unless the carrier frequency is negative This mode uses the Murphy interpreter to convert script data to Morse DFSK BEACON The Exciter transmits DFSK often called dual frequency CW keying using Morse The message sent is contained in the beacon script and this mode uses the Murphy interpreter to convert script data to Morse The keying speed is controlled by the K command while the A command sets the FSK offset Dots are transmitted on the nominal frequency set by the F command while dashes are shifted up in frequency
23. RECEIVE command turns the transmitter off if it is on It has no effect on any other parameter The Exciter does not echo this command RX is used in conjunction with T TX to control the Exciter externally User Manual Page 40 In beacon mode the data and commands are received internally from the beacon script which is stored in the EEPROM memory Operation is exactly the same as sending external commands except that the data is processed internally The beacon in the ZL1BPU LF Exciter is very powerful The command interpreter that receives the data from the stored message and interprets it can handle coded Morse graphics and data in addition to a range of commands in fact just about anything but text The message is in a compiled form designed for easy interpretation by the micro and how the data is interpreted depends on the current mode The PC program MAKEBON is capable of compiling and recording beacon messages in the required format at least for Morse modes For more information on the beacon modes see Chapter 5 Beacon Message There are six beacon mode commands that can be used in the message script In general these work in the same way as their KISS command counterparts The differences are that they are executed automatically and the syntax is different The commands can be in any order and can be distributed throughout the message No transmission time is lost when commands are processed b
24. User Manual ZL1BPU LF Exciter User Manual M Greenman CSc ZL1BPU July 2002 Page 1 Contents Introduction Applications Theory of Operation Consiruction Options Programming and Setup Operation User Software Appendices 0 Glossary 2 Notices This Manual is Copyright M Greenman 2002 and must not be copied republished or distributed in whole or in part without permission The firmware for this project code programmed into the micro controller is also Copyright M Greenman 2002 and is available from the author via for a nominal 10 charge for which you get lifetime email support Firmware can of course be copied and can be passed on free of charge to others but you should not expect support from the author unless you purchase a copy direct from the author Source code for this project the assembly code include files etc everything to reassemble the firmware is thoroughly commented and available from the author for 30 The source code is written in assembly language for the ATMEL AVRASM Windows compiler While the information in this manual is believed to be correct and the author s prototype Exciter works to his entire satisfaction the author accepts no liability for errors or failure of any constructor s copy of the design to perform as expected Support is limited to the design as described and to firmware purchasers as outlined above This Manual was written in Mic
25. Values above this will cause the signal to have bad aliases spurious signals or have a negative frequency In sweep mode FREQUENCY sets the frequency of the first step the one that corresponds to the SYNC signal Following steps will normally be higher in frequency If the FREQUENCY value used is negative 1000000 required value the sweep steps will be negative i e down in frequency rather than up H HELP Syntax H The Exciter sends a simple HELP message listing all the available KISS mode commands Once the message has been sent the Exciter resets so the start up message also appears The syntax for each command is given in the list K KEY Syntax Knnnn The KEY command sets the beacon mode keying rate baud rate The value nnnn is hexadecimal 0000 to FFFF The beacon mode uses its own baud rate generator the symbol clock This clock is generated externally to the micro and is normally 64 Hz 15 625 ms The value given for the K command is the number of 15 625 ms periods required per symbol so the resolution is also 15 625ms The formula for calculating the required value is KEY 64 baud rate 1 6 Hence K0001 the highest speed possible gives a baud rate of 32 baud and can be used for 26 WPM Morse 3 sec dot QRSS requires KOOCO 10 bits minute User Manual Page 34 and JASON 11 8 sec symbols KO2F0 By the way to calculate the baud rate for Morse use this formula BAUD 1
26. are transmitted differs In Feld Hell just one frequency is used and the dots are either transmitted or not transmitted with very precise timing The receiving software has to scan vertically and horizontally displaying signal strength as brightness Only slow Feld Hell is possible with the Exciter and special receiving software will be required In the example in Fig 5 1 the text is transmitted at 32 dots per second K0001 and the receiving software scans at four columns per second The signal was very weak hence the noise on User Manual Page 24 the signal Feld Hell is not an especially sensitive mode but is quite tolerant of man made noise nu 5 EN E prr E wr ME E A Fig 5 1 Weak Feld Hell transmitted by the Exciter In MT Hell each dot in the column is transmitted on a different frequency and the signal is received with a spectrogram program such as ARGO see Fig 5 2 Because there is no receiver column scanning timing is very relaxed MT Hell is not as sensitive as many of the modes received with ARGO but is a lot more fun Hell format consists of eight dots per byte which creates one column The LSB bit of the byte represents the lowest dot in the column It is normal to use five or seven active dots per column for lower case use the lowest two dots for descenders as on and q There will almost always be two unused dots at the t
27. as a self contained beacon even when power is removed and reapplied I Send ID This is a program command The program asks you for a short line of text such as de ZL7ABC which is then sent as ASK Morse at about 8 10 WPM If the Exciter is in the middle of a beacon message this command will temporarily take over the Exciter and will leave the TX off at the end of the message so the following beacon text element may be missing Any short line of text can in fact be sent The keying speed will depend on the speed of your PC H Help Sends a short help message to the PC screen ESC Exit Quits the program and closes the files and communications port Using the Program The Exciter Mode Commands Now look at the lower group of commands on the MAKEBCN EXE screen Fig 8 1 These directly control the LF Exciter and are accessed via the Function Keys usually in a row at the top of the PC keyboard The first five are mode commands and will instantly switch the Exciter into a beacon keying mode The three modes ASK FSK and DFSK are all Morse modes the other two are bit mapped graphics modes used to send simple images or various MFSK or Hellschreiber modes All modes except HELL can be received on a Spectrogram display JASON mode is not included since it is not supported by MAKEBCN 15 You need to use the JASON software by I2PHD and IK2CZL User Manual Page 51 The F10 key returns the Exciter to mode MO allowing only
28. by an inter character space the inter word space is six dot times Some characters are interpreted as inter character spaces 0x01 while others are ignored completely 0x00 The table below is represented in hexadecimal Lower case characters should be coded as upper case SP 01 0 A 06 Q 1B 00 1 3E B 1 R 0A 52 2 611 15 S 08 00 3 38 D 09 T 0 cal 4 30 02 U 0 0l 5 20 14 V 18 amp o 6 21 G 08 WOE 5E 7 23 H 10 X 19 2D 8 27 04 Y 1D 60 9 OF J 1E Z 13 s 01 47 K 0D 00 AR 2A 35 L 12 SK 68 73 lt 00 M 07 00 61 BT 31 05 00 6A gt 00 OF 6C 7 29 7 4C P 16 00 Table 9 1 The Morse Coding Table User Manual Page 66 Hell Font The suggested font is a 5x7 low resolution Hell font Characters are listed in ASCII order starting at ASCII 32 space Five bytes are shown for each character represented in HEX Trailing spaces can be ignored making the font proportional Always include one byte of 0x00 zero between characters to act as a character space For double width characters repeat each byte for Feld Hell four or more repeats The example in Fig 5 1 has four identical bytes per column Note this is NOT the same font as that transmitted by EXC EXE SP 00 00 00 00 00 0 0E 13 15 19 0E 00 1D 00 00 00 1 00 10 1F 00 00 a 00 18 00 18 00 2 03 15 15 15 09 0A 1F 0A 1F 0A 3 15 15 15 0A 00 08 1
29. con use messages that are Morse based use MAKEBCN EXE which offers real time control of frequency can turn the transmitter on and off but most importantly can accept a text message file compile it into commands and Morse in Murphy format and download it to the Exciter For real time QSOs using a PC to control the Exciter there are two choices the DOS program EXC EXE by the author and the Windows program WinEXC EXE by Con ZL2AFP not documented here They are generally similar The DOS program will operate under Win 3 1 95 and 98 in a DOS box Furthermore the program can be run concurrently with ARGO or another Windows spectrogram program for reception 14 There is a wide variety of such programs available for free download at simtel man szczecin pl pub msdos commprog User Manual Page 47 For real time JASON operation you can use JASON 0 94 by Alberto I2PHD and Vittorio IK2CZL This software supports the ZL1BPU LF Exciter command protocol for transmitting so with a serial cable connected to the Exciter you can transmit from the Exciter and receive using the sound card directly from the LF receiver Calibration The actual frequency of the Exciter reference crystal does not usually matter as the software used to control the Exciter can calibrate out or compensate for any error Only with KISS mode manual control will you need to know the actual frequency accurately that is unless you simply adjust the frequency with t
30. cording the signal obigatory The resolution and extreme stability of the ZL1BPU LF Exciter Sweep Generator are perfect for sweeping such difficult applications something most conventional even expensive sweep generators struggle to achieve User Manual Page 46 8 Software Micro controller Firmware There is only one executable file required EXC_Dnn hex where is the version number As explained earlier the only hardware dependent parameter is the serial communications data rate affected by the crystal frequency which is programmed separately during setup Hence there is only one build of the firmware While an EEPROM image EXC Dnn eep is also supplied this is not necessary and only sets the default crystal frequency parameters and loads a demonstration beacon message PC Control Several control programs are available For KISS operation any dumb terminal at 9600 N 8 1 will suffice For portable and field use the author uses a small DOS palm top computer with built in terminal emulation HP 200LX with great success and there are many DOS terminal programs that work well on DOS computers and laptops remember Windows computers of all types Win 3 1 Terminal is recommended it works well on Win 3 1 95 98 and 2000 and is much easier to use than the one normally supplied with the later versions of Windows By the way most packet radio programs will also work well For general bea
31. ct the DB25 end of the cable to the PC printer parallel port and the 10 way header to the Exciter programming header Make sure the cable is the right way round on the header no damage will be done if it is wrong but nothing will work If you have two computers or can run two applications at once connect up the Exciter serial port to a PC serial port You will need a modem serial cable pin to pin with no crossover NOT a null modem cable Run a Terminal Emulation program Windows 3 1 Terminal is ideal setting it to the correct port and the speed you intend to use This will allow you to monitor progress during programming Run the ISP software ISP EXE There is also a DOS version the most recent version supports 32 bit operating systems The author recommends V2 65 which will work on a 486 PC running Windows 3 1 as well as later computers Make a project from the menu Project New Project selecting AT90S2313 as the device 10 ISP EXE V2 65 available from user cs tu berlin de sirhenri sides up_avr avrisp zip The latest version is available from www atmel com atmel products prod203 htm www gsl net zl1bpu micro for a suitable cable 12 There have been problems with port timeout errors with later versions User Manual Page 28 Devices Supported xi Devices Supported AT90512007A 1905 2313 AT905 L52323 AT90S LS2343 AT90S 4414 AT90S LS 4434 05 1 52333 AT9057LS4433
32. d 30 minutes warm up will suffice for JASON Crystal Frequency The crystal X1 can be any frequency from 10 MHz to 16 MHz provided a the micro controller will operate that fast all the ones tried so far have operated at 16 MHz and b the frequency allows an accurate 9600 bps communications rate to be generated When choosing a crystal remember that the maximum frequency that can be generated cleanly is about 1 30 of the crystal frequency for example about 430 kHz using a 12 8 MHz crystal Since the power amplifier response drops off above 250 kHz this is only an issue if you plan to use the unit without the amplifier or with a lower frequency crystal Once the crystal is chosen the communications rate to the PC which depends on this crystal has to be set The best rate to use is 19200 bps as this provides high performance with minimal difficulty with PC speed lead lengths and so on For some crystal frequencies lower speeds will be necessary as the speed error increases with speed For example with a 10 0 MHz crystal 9600 baud is the highest practical speed The default value is 9600 bps with a 12 8 MHz crystal User Manual Page 23 In order to operate the unit with I2PHD and IK2CZL s JASON you must use 9600 bps so if you contemplate using JASON at any stage stick with 9600 bps The calculation for the micro controller UART divider goes like this UART Divider fcrysta UART Speed x 16 1 4 For example
33. d a negative number the phase retards and the register counts down If we add zero the phase stays constant The Look up Table The number in the phase accumulator register represents the current phase of the output signal By using this value to look up a number in a table it is possible to generate any periodic waveform with a frequency that corresponds to the rate at which the counter overflows and repeats the same phase In the ZL1BPU LF Exciter one table is used containing a sine wave Eight bit values are used The phase accumulator is 24 bit and after each phase step the phase value using the most significant 8 bits is looked up in the sine table and the corresponding value placed on the outputs In the Signal Generator the same technique is used but any one of four different tables can be selected for different waveforms Limiting the output and the phase lookup value to 8 bits has no appreciable effect on the output The D A Converter The micro controller output is a digital number representing an instantaneous sine value which still must be converted into an analog value This is the job of the Digital to Analog Converter In the Exciter a simple resistive network does this job and generates a 256 point waveform with very good linearity The signal is User Manual Page 10 5V and is completely flat in frequency response from DC to over 400 kHz The quality of resistors used has a direct effect on the purity of th
34. d keying pulses superimposed not what is wanted for narrow LF transmissions The solution is to use a slow external clock source refer to Fig 4 4 This could be crystal controlled for example using a 32 768 kHz watch crystal but it has been found that a simple stable RC oscillator is sufficient In this design the oscillator runs at about 2 kHz and is divided down to provide a stable 64 Hz clock to the micro controller The internal timer further divides this down so the internal symbol clock can be from 64 Hz down to one clock every 1024 seconds The range can be increased and decreased by selecting different divider outputs but the range provided should cover all practical requirements The rate at which symbols occur is called the baud rate To define the required baud rate you have to specify the division ratio for the micro controller timer Obviously with a 64 Hz reference one dot or data element per second will require dividing by 64 in the timer Here s the general formula Timer Value z 64 baud rate 2 The number the timer needs is actually 65536 minus this number it is a 16 bit timer but the micro controller works this out For modes where you need to express the baud rate in so many second dots dot period as for QRSS the formula becomes Timer Value z 64 x dot period 3 User Manual Page 14 As an example to generate 3 second dots use timer value of 3 x 64 192 00 The values for the
35. d so the frequency resolution is given by the relationship Resolution Ferysta 9 x 2 Hz 1 With a 12 8 MHz crystal frequency this works out at 0 0847710503472 Hz To calculate the value to send to the Exciter for any given frequency you need to divide the frequency you need by this value with all the many decimal places Why so many decimal places Well to generate accurate frequencies with all the precision necessary we need the decimal places Here s an example We want to generate 136 000 kHz Let s just divide by 0 084 and see what happens The result is a command value of 1619048 to the nearest integer The frequency generated converting back again will be 137 248 kHz well over one kHz in error Using the correct division value we end up at 135 999976 kHz only 0 024 Hz in error This small error is caused by the need to use integer numbers for the phase addition remember the 0 084 Hz resolution We only need to think about these awkward numbers when entering frequencies manually The PC software does all the hard work for you with full resolution 8 See http www myplace nu avr User Manual Page 12 Hexadecimal Calculations The Exciter KISS commands use hexadecimal numbers These are easiest for micro controllers to manage but mere humans will require some assistance Take the previous example transmitting a carrier on 136 000 kHz From the above formula 1 we know the command
36. dots are sent key down non visible spaces as key up The mode is extremely immune to noise since the data is interpreted by eye The name derives from the inventor Rudolf Hell and the first major use of this exact mode for military field transmissions in the 1930s See MT Hell Program which operates in a fixed program device such as a micro controller See software Fast Fourier Transform A mathematical technique used to convert signals from the time domain to the frequency domain in the same manner as a spectrum analyser Frequency Shift Keying Morse sent this way has key up on one frequency and key down on another Numbers expressed to base 16 which are more readily understood by a computer than decimal base 10 A method of representing hexadecimal values by a number 0 9 or letter A F Two such characters are used to express each byte 00 to FF Incremental Frequency shift Keying A type of MFSK where the information sent is not in the actual frequency transmitted but the incremental frequency difference between the event and the previous event This technique is resistant to frequency drift Page 70 KISS LF LSB MFSK MT Hell PLL PSK QRS QRSS Software Source Code Symbol TCXO UART User Manual Keep it Simple Stupid A term used to describe simple control protocols for microprocessors and micro controllers which are human readable as well as machine readable Low frequency
37. e The default modes and their names are arranged so the transmission looks correct at the corresponding ARGO speed for example QRSS3 and DFSK3 are readable on ARGO 3 SEC mode Examples MORSE 10 WPM MORSE 0 0 0 1 QRSS 3 SEC DOTS QRSS3 0 0 3 QRSS 10 SEC DOTS QRSS10 0 0 10 DFSK 3 SEC DOTS DFSK3 2 32 3 DFCW 10 SEC DOTS DFSK10 2 10 10 MT HELL 3 SEC MTHL3 4 32 0 6 MURRAY 3 SEC MURRS 4 32 1 MURRAY is a fun mode using 5 bit ITA 2 code transmitted for visual reception like reading paper tape The final four lines in the setup file contain the four pre programmed messages There is one message per line and they must be surrounded in quotes The messages can be 255 characters long but remember they may take ages to send but only the first 20 so are shown the screen When these messages are used they are not copied into the transmit buffer but send the selected message over and over again until you quit the program or change from message to keyboard Using the Program The Screen There are three areas to the screen see Fig 8 2 The top and centre show the current operating mode and message the current frequency setting and the transmit status TX RX You can see the lists of modes and messages from which you select in turn with a function key The frequency is displayed to 1 mHz resolution and is the actual carrier frequency achieved by converting your requested frequency to hexadecimal sending i
38. e beacon script when power is applied The Sweep Generator W setting is not stored so the unit cannot default to Sweep Generator mode W defaults to zero at power up The other parameters used by sweep mode are stored T TX Syntax T The TX or TRANSMIT command turns the transmitter on if it is off It has no effect on any other parameter The Exciter does not echo this command TX is used in conjunction with X RX to control the Exciter externally For example to send ASK Morse a series of T X TX T X T X commands correctly timed of course can be used to send perfect Morse up to at least 35 WPM W WIDTH Syntax Wmm Sets the WIDTH of the Sweep Generator mode by setting the number of sweep steps The value mm is two hexadecimal characters representing a value 00 to FF 0 to 255 although widths of greater than 30 or so steps aren t generally useful for conventional sweep generation The start frequency for the sweep is set by the F command sweep dwell time by the A command and the sweep step size by the K command Typical values are WOA for 10 steps and W14 for 20 steps giving one or two steps per scale division on the oscilloscope screen Small values of W can be used to simulate FSK and MFSK modes For example audio frequency 50 baud 170 shift RTTY with 2125 Hz MARK can be simulated with W02 AF8 K07E5 F0062B1 W01 has no effect 00 turns sweep mode off User Manual Page 39 X RX Syntax X The RX or
39. e is an excellent application note introducing Direct Digital Synthesis and function generation at ftp thinksrs com PDFs ApplicationNotes dds padf User Manual Page 9 The high speed adder technique gets around this limitation and relies the Nyquist Criterion for proper operation Nyquist proposed that any periodic waveform could be reconstructed from at least two samples of the waveform per cycle of the highest frequency component In practice more samples are required as it is difficult to conceive sufficiently good interpolation filters to reconstruct the waveform accurately Three samples seem to be sufficient So how does this affect the high speed adder Well if we arrange to add a fixed number into a register at every high frequency clock event and let the register overflow when it is full the value in the register will appear to ramp up at a rate that depends not only on the clock frequency and size of register but on the value added each time You can imagine the conventional resettable counter is simply an adder which only adds 1 Such a register is called a phase accumulator and the value added each time the incremental change in phase represents the requested operating frequency see Fig 3 1 This technique allows the ramp represented by the phase accumulator count to progress in effect change phase for every clock event If we add a positive number the phase advances the register ramps up if we ad
40. e per step can be from 1ms to about 200ms The versatility of the sweep generator is such that you can even generate test signals for RTTY and other FSK modes 6 See www qsl net zI1 bpu micro SIGGEN Siggen htm or http sharon esrac ele tue nl mirrors zl1 bpu micro SIGGEN Siggen htm User Manual Page 8 3 Theory of Operation The Exciter uses software simulation of the Direct Digital Synthesis DDS technique to generate sine wave radio signals with very high precision The DDS system whether in hardware or software uses several building blocks high Speed adder a look up table an analog to digital converter and a low pass filter There are three main functional sections to the Exciter unit the micro controller a symbol clock and the power amplifier Clock 12 8 MHz High Speed Adder Phase Accumulator D A Converter dr Sine Wave Output Fig 3 1 DDS Block Diagram The High Speed Adder Early digital synthesis using digital techniques was achieved using resettable counters the same technique still used today for phase locked loop synthesis The counter can be made to give an output every input clock events where n must be between 1 and the maximum possible count of the counter The trouble with this technique is that resolution is very limited in fact limited to exact fractions of the clock so that a very high frequency clock is necessary for even modest resolution 1 Ther
41. e signal Frequency Limitations The way the adder operates low frequencies are generated by adding small values to the phase accumulator The smallest increment is of course one In the ZL1BPU LF Exciter design a large phase accumulator 24 bit is used andso a step of one works out to 0 084 Hz We call this the DDS Resolution the mathematical derivation is covered in the next section A step of zero of course results in a zero phase change zero frequency or DC output a step of one gives a frequency of 0 084 Hz and so on Higher frequencies involve first fewer samples per step on the sine wave and higher still fewer and fewer samples per sine wave The maximum frequency is limited by the Nyquist Criterion and practical low pass filters to about one third of the adder clock frequency or about 400 kHz in this design All frequencies from zero to 400 kHz can be generated with the same 0 084 Hz resolution As we approach 400 kHz the output contains fewer and fewer samples per sine wave If we continue on up in frequency you can try this as there is actually no limit to the numbers you can give the Exciter an image frequency is generated in addition to the desired output This frequency faock faesied gets stronger and stronger and closer and closer to the desired output until at exactly one half the clock frequency the image and desired output coincide It is actually possible to intentionally select the image frequency as an o
42. e start frequency the number of sweep steps it has discrete steps not a linear sweep the frequency step size and the dwell time the time spent on each step The first step is always the lowest frequency unless you set the frequency to be negative Three of the Sweep generator commands are normal mode commands recycled while the third is unique to Sweep mode The Sweep Generator commands are described briefly below and in more detail earlier in the Chapter under KISS Mode A ADD Sets the dwell time time per step User Manual Page 44 FREQUENCY Sets the sweep start frequency exactly in normal mode K KEY Sets the frequency step size in resolution steps W WIDTH Sets the number of discrete steps in the sweep or turns off the Sweep mode Perhaps one of the most useful features of this Exciter Sweep Generator mode allows you to sweep antennas filters and antenna tuners for correct adjustment When used with a Return Loss Bridge like an SWR meter with no meter or an Impedance Bridge you can plot the performance of your antenna and feed system very simply Unlike a conventional sweep generator this unit generates discrete frequency steps and they are also very precise in frequency There can be from 2 to 255 sweep steps although Sweep mode is best used with 20 discrete frequency steps W14 The sweeping occurs continuously with each frequency generated for the set dwell time typically 5ms T
43. e the R 2R resistors will fit R1 9 and R10 16 The micro has a natural IN side and an OUT side in this design which makes layout easy In Fig 4 3 pin 1 of U2 is bottom left In Fig 4 3 the symbol clock generator U4 is at the bottom right with its RC timing components C15 R35 R36 above U4 pin 1 is bottom left on the chip To the left at the bottom is the simple discrete transistor RS232 interface wired to the connector on the back panel Just above it is the small 5V regulator U1 No heat sink is required for the regulator 49052313 10 ume X1 78105 RSkad UA Interface HEF4060 Fig 4 3 The circuit board layout User Manual Page 20 Power amplifier U3 requires no heatsink U3 is flanked by the capacitors C13 the left and C14 on the right A short length of RG174 coax to the output socket is used to select the correct tap on output transformer L1 simply soldered as needed Finally the power busses are run under the board using tinned copper wire The 12V DC input is at the bottom left in Fig 4 3 under the RS232 connector and runs down from the rear panel connector halfway up on the left and the 12V and 5V busses run up the left of the board The OV connection is visible at the bottom right of the board where there s a handy link for use as a test equipment ground and the ground buss runs up the right of the board with branches out to each device The secondary of the output t
44. ecessary adjust the value of R37 so the amplifier just clips at full output No damage will result if the load is not connected 12V DC In To PC 12 MHz 5V Regulator Or microcontroller Reference 2048 Hz Microprocessor AT90S2313 Level control Fig 4 4 The Exciter Block Diagram User Manual Page 22 5 Options you choose to use the Exciter for real time QSOs or as signal generator it will not really matter what crystal frequency you use nor what is stored in the micro message memory used by the beacon generator All you need to do is ensure that the communications rate is set for the crystal you use You should use a good quality crystal not a cheap micro crystal If you do not wish to patch the micro controller setup use the default frequency 12 800 MHz however you wish to use the built in beacon you will have to decide what the main purpose of the unit is before you choose the crystal frequency and whether you need a simple crystal or a TCXO For precise 0 1 Hz steps use 15 0994944 Mhz For hexadecimal precise steps 1 16 Hz use 9 437184 MHz For really accurate JASON transmissions use 12 700 MHz For most other purposes use 12 800 Mhz TCXO references are easily obtained at 12 800 MHz and would be the most appropriate reference to use for a beacon operated at a remote site or where very high stability is necessary such as for QRSS120 A good quality crystal an
45. en in the message if you wish Recording messages that include the image modes is rather more complex and needs to be done by hand input of the data bits The author can code a mixed mode message with callsign in MT Hell or Feld Hell in under 30 minutes So it s not too difficult JASON is the most complex and really requires some method of capturing the output of the I2PHD IK2CZL JASON program While the transmitter power level is not programmable it can be set to any desired level via a front panel control the only front panel control There are three programmable digital outputs so it would not be difficult to use these to control power level switch antennas and so on Since the message is stored in memory just apply power connect and tune the antenna and the beacon will run with no further intervention If you want to operate the beacon for a fixed period each day simply operate it from an AC supply fed from a time clock The message always starts at the beginning when the micro controller is reset Real Time Transmitter One watt is not much power for LF operation and most users will prefer to drive a high power transmitter The advantages of using this device as the exciter for a high power transmitter are the versatility of operating modes extreme stability precise frequency setting and the very clean carrier generated 5 See the list of Beacon commands in the Appendix User Manual Page 6 ZL1BPU LF Exciter RF o
46. er Knnnn KEY The beacon mode keying baud rate where nnnn is 0 0000 to OxFFFF Resolution is 31 25ms but is dependent on the symbol clock generator frequency typically 32 Hz Hence K0001 gives a baud rate of 32 baud 3 sec dot QRSS requires KOOCO and JASON 11 8 sec symbols KO2F0 In Sweep Generator mode sets the frequency increment in resolution steps as for the F command but range is limited to 0000 to KFFFF over 5 kHz step Mn MODE Sets the beacon mode where n is a number 0 to 6 0 Beacon Off Continuous carrier controlled by A F T W and X commands 1 ASK On Off single frequency keying beacon message in Morse 2 FSK Continuous carrier FSK keying beacon message in Morse 3 DFSK Dual frequency on off keying beacon message in Morse 4 MFSK Eight frequency bit mapped scanned MFSK mode e g MT Hell 5 HELL On Off single frequency bit mapped keying e g Feld Hell 6 MFSK IFK MFSK data frequency shift in resolution units e g JASON User Manual Page 62 Sets D outputs PD2 PD4 according to value least significant bits of value p as follows 0 PD2 0 PD3 0PD4 0 4 PD2 0 PD3 0 PD4 1 1 PD2 1 PD3 0 PD4 0 5 PD2 1 PD3 0 PD4 1 2 PD2 0 PD3 1 PD4 0 6 PD2 0 PD3 1 PD4 1 3 PD2 1 PD3 1 PD4 0 7 PD2 1 PD3 1 PD4 1 p values above 7 work but upper bits are ignored R REPORT Requests a message giving the current settings Reports MW and F S STORE Store current settings Saves FREQUENCY OFFSET
47. er In this view the front panel is to the left and supports the POWER control top and POWER LED the RFOUT connector bottom and TX LED The back panel to the right supports the RS232 communications connector top the power connector centre and the SYNC TX output bottom There is plenty of room User Manual Page 18 remaining in this 210 x 180 x 55 mm case perhaps for an LCD display controller board or a 10W power amplifier gt x z z z gt v gt xz d lt 2 gt K Uu Fig 4 2 Inside view of the LF Exciter This view is a detail of the circuit board rotated with power supply top left RS232 circuit below it and the symbol clock IC bottom left You can clearly see the R 2R resistors laid out to the right of the micro controller the crystal on the left of the micro and the amplifier circuit to the far right The amplifier output transformer with its taps is very obvious on the right The transformer need not be this large it is this size simply for convenience The connector above the micro is the programming header It is point to point wired to the micro under the board and is only used when you wish to change the firmware NOT for recording beacon messages which are loaded via the RS232 port User Manual Page 19 Assembly The order in which the board is assembled isn t especially critical but do start with the IC sockets and plan out wher
48. erating frequency 0003 E8 Mid byte of default operating frequency 0004 33 Low byte of default operating frequency 0005 00 Default mode 0006 18 Default offset FSK offset MFSK step size 0007 52 UART data rate 9600 bps 0010 FF Start of beacon message 007F FF Highest possible location of beacon message Table 9 3 EEPROM Locations Brief Exciter Specifications Spectral Purity Second harmonic 42dBc third harmonic 50dBc no low pass filter All harmonics at least 50dBc with low pass filter Below 20 kHz all harmonics 60dBc or better Random spurii better than 60dBc close in noise below 60dBc within 1 Hz Sampling rate 1 11 MHz Nyquist frequency 550 kHz Sampling clock and alias image at 1 4 MHz 42 and 54dBc respectively Operating Range 0 08 Hz to 400 kHz in any step size with a resolution of 0 08 Hz Power amplifier response drops off below 7 kHz and above 250 kHz 500mW power bandwidth 10 kHz to 200 kHz and depends mostly on the output transformer and coupling network Power Output Amplifier Up to 1W into 8 50 Ohm load Power level adjustable over more than 60dB range using a DC control pot Direct Output without power amplifier is 5V into 1M Ohm or 1V RMS into 1k User Manual Page 68 Digital Outputs 8 bit sine data to D A converter By changing the sine table it is possible to generate push pull non overlap square wave drive at 20mA with any one of four user selected duty cycles
49. es with switched antenna tuner settings The outputs are CMOS level and can drive LEDs directly The outputs can sink or source 20mA see the circuitry for the TX LED in the schematic In order to operate relays a driver is required The circuit below is recommended 12V D1 1N4148 PD2 PD3 or PD4 Fig 5 3 Suitable relay driver Controlling the outputs is very simple but be aware that the PORT command and the beacon script command are binary and control all the outputs at once so you have to check all the bits you need to decide what number to send The simplest application controlling one relay connected to PD2 requires only sending two commands PO or 0 for off and P1 or FBO1 for on User Manual Page 27 6 Programming and Setup This procedure assumes you use the same programming tool as the author 9 Since this is free i s a reasonable assumption If you use other tools you will obviously need to be familiar with them You will need e The ATMEL ISP AVR programmer ISP EXE V2 65 or similar e programming cable e The EXCITER firmware EXC_Dnn HEX and EXC_Dnn EEP available from the author is the firmware version currently 5A e APC running Windows 3 1 95 or 98 to run the programming software The EEP file is not strictly necessary although it includes default values for 12 8 MHz crystal operation and a demonstration beacon message listed in the Appendix Conne
50. ets the offset used for FSK and DFSK modes and the incremental offset per bit in MFSK mode The range is zero to about 25Hz Values of about 30 divided by the dot period are recommended User Manual Page 53 F8 SPEED Sets the dot period in seconds The program assumes the dot clock is 64Hz The range is from about 0 05 to 1000 seconds For normal speed Morse use the following table Period Command Speed 0 03 sec K0002 35 WPM 0 05 sec K0003 25 WPM 0 07 sec K0004 15 WPM 0 10 sec K0006 12 WPM 0 15 sec K000A 9 WPM 0 20 sec KO000D 6 WPM Table 8 1 Keying Speed F11 TX Turns the transmitter on If used with the beacon running will only remain active until the next beacon element F12 RX Turns the transmitter off If used with the beacon running will only remain active until the next beacon element Using the Program Making and Sending Scripts The F9 Function Key provides a means of making and downloading beacon messages These are otherwise fairly laborious to make involving looking up each Morse character in a table and entering the values manually with the Exciter B command which is both boring and prone to error The SCRIPT command works in two phases First the requested file is opened read and converted into Morse and commands if included see later The size of the message is checked to see if it Will fit into the Exciter memory and will be rejected if
51. h programs are designed to operate in conjunction with ARGO which is used for receiving In fact you can even operate full duplex on just one computer if the radio equipment will permit Signal Generator The RF amplifier in the ZL1BPU LF Exciter has an extraordinary control range By simply adjusting the drive level it is possible to reduce the output to fractional microvolts There is little leakage from the Exciter so it is possible to reduce the output way below the receiver noise threshold A fixed 10dB or 20dB attenuator on the transmitter output is a good idea in order to protect the receiver from damage Using any of the suggested PC software you can tune the Exciter to any frequency you desire within the range to 400 kHz The output is substantially flat from 10 kHz upwards If audio frequency capability is of interest add a small line transformer across the output transformer L1 The 1W linear amplifier is actually an audio power amplifier User Manual Page 7 It is not especially difficult to write your own program to control the transmitter or generate special complex transmission modes This can be done on the oldest PCs using nothing more than GWBASIC which came with early versions of DOS The LF Exciter is also fully compatible with the Signal Generator firmware which can be used where sine square ramp or triangle waveforms are necessary The Signal Generator also includes the sweep generator mode Note that differen
52. haracters The speed setting is critical to the appearance of the text The dots are sent in the same order as MFSK but all on the same set frequency Cannot be received on a spectrogram needing a HELL style amplitude sensitive receiver You could capture the output of this mode to create a Feld Hell beacon message User Manual Page 52 F10 Beacon Disables the built in beacon keyer Allows the Exciter to be directly controlled with the F6 F7 F11 and F12 commands by the I ID command or by the EXC EXE program Using the Program The Exciter Settings These commands allow direct control and beacon mode settings to be changed These settings will be lost on power down unless the SAVE command is sent These same commands and the Mode commands of course can be embedded in the beacon message so if the Exciter does not seem to obey any of the commands you set check that it is not being countermanded by the beacon message F6 FREQ Allows the Exciter synthesizer carrier frequency to be set with great precision The resolution is less than 0 1Hz The value is entered in Hz This value is then divided by the synthesizer resolution depends on the clock frequency converted to hexadecimal and sent to the Exciter Fortunately the user does not need to worry about that Negative frequencies can be set and result in the correct carrier frequency but the SHIFT works in the opposite direction in FSK DFSK and MFSK F7 SHIFT S
53. he Exciter The ZL1BPU LF Exciter is simple to build There are four ICs and a handful of other components The parts are not difficult to obtain Construction is achieved on a simple project board about 100 x 150mm in area with room to spare No surface mount components are used There are no adjustments to make There is only one front panel control and four connectors RF OUT SYNC or TX ON signal DC power and RS232 communications Level of expertise for construction MODERATE NOTE No printed circuit board is available and none is necessary Fig 1 1 Front view of the completed Exciter User Manual Page 5 2 Applications There are four main uses for the ZL1BPU LF Exciter Stand alone beacon keyer modulator VFO exciter and transmitter all in one Real time QSO transmitter or VFO exciter e Signal generator e Sweep generator Beacon Transmitter Since the unit has over 100 bytes of user recordable message memory just about any message you want in any mode you want can be recorded in Indeed since the beacon is smart you can send several different modes by including mode changes and even frequency changes in your beacon message Recording messages for standard LF modes such as Morse QRSS and DFCW is straightforward using the MAKEBCN software provided by the author This compiles and downloads the message and allows you to set the keying parameters speed shift and operating frequency ev
54. he F command until the frequency counter or receiver indicates that the transmission is where you need it Start by editing the file EXC SET used with all the PC control programs placing the nominal crystal frequency in Hz in line 3 of the file Using one of the PC control programs see descriptions below operate the Exciter and cause it to transmit on a convenient frequency by giving the PC program the commands for that exact frequency For example if you use a nominal 12 8 MHz crystal send the command to operate the Exciter at 128000 Hz 1 100 or 160000 Hz 1 80 Read the transmitter output frequency with a good frequency counter and note the reading Multiply this by the ratio between the nominal crystal frequency and the actual operating frequency 100 or 80 in the examples Then edit the EXC SET file and replace the value on the third line with this new value Now when you run the PC control program again it will read the EXC SET file again and exactly compensate for the error in the crystal The better the actual transmitted frequency can be read the better the program s control accuracy If you have chosen a crystal to give exact 1 10 or 1 16 Hz steps you will need to trim the crystal Set the nominal crystal frequency the value that gives the correct steps as precisely as possible in the EXC SET file set the transmitter to operate on aconvenient frequency such as 200000 Hz and adjust the trimmer for exactly that
55. he TX LED and SYNC output are turned on for the duration of the first step Using an oscilloscope trigger the sweep off the SYNC output and with the sweep set to 10ms div the 20 steps will nicely line up across the screen A1F works well with a 5ms div time base You can also make the sweep generator sweep backwards by setting a negative start frequency although why one would need to do this isn t obvious It will also sweep through zero but once again that s not much use For audio sweeping try setting the start frequency to zero F000000 and use a narrow sweep increment e g K0498 for 100 Hz step So here s an example sweep from zero to 2000 Hz in 20 steps with 5ms on each step F0000 K0498 W14 You can also write a PC program to control the Sweep Generator however you wish All the sweep generator parameters can be adjusted while the sweep generator is running There might be the odd hesitation if for example you set it User Manual Page 45 to 10 steps while it is already on step 19 Remember also that the generator will always stop while you actually enter the commands Another hint there is a short transient every time the frequency is stepped so the fewer steps and the slower the step rate the cleaner the results will be For high resolution sweeping of very narrow filters such as crystal filters slow sweep rates are necessary This in turn may make use of a storage oscilloscope or other means of re
56. hen you apply power to the Exciter the micro will send a little message saying EXCITER 05 gt or something similar If the message is garbled check that the computer data rate is correct and if it is go back and check the programming value for the data rate User Manual Page 21 in the micro controller see the section on programming To check that it is listening as well as talking type H on the keyboard and the Exciter should respond with its list of commands the Help information Now you are in business Fool around with the F command a little and try out different frequencies At this point you might like to study the Serial Command List in the Appendix in order to understand how the unit is controlled If the output from the point labelled DDS OUT is not a reasonable sine wave investigate the connections to the R 2R network resistors and check that the values are correct Just one resistor wired incorrectly will destroy the nice sine wave Having good resistors here makes all the difference to the performance Finally when you are happy that all is well and you have nice clean sine waves coming out turn off the power plug in the power amplifier U3 add a load to the output and with power applied and the carrier on use the T command adjust the taps for maximum power with the power level control at full output maximum resistance The power output should exceed 0 5 Watts from about 10 kHz to well over 250 kHz If n
57. ig 8 3 it offers just about the same functionality with drop down lists and mouse clicks instead of function key operation WinEXC uses the same EXC SET file as MAKEBCN and EXC and it must reside in the same directory or folder as the executable program The program is very small is much nicer looking than EXC EXE and it makes no nasty changes to the Windows Registry 17 Contact Con at zl2afp internet co nz User Manual Page 60 DDS LF Exciter 181 400 00 Hz TEST de ZL1BPU Fig 8 3 The WinEXC screen User Manual Page 61 9 Appendices Serial Commands KISS commands Axx ADD Add offset of xx resolution steps where xx is 00 to FF In Sweep Generator mode sets the sweep dwell time time per step Resolution is about 1 12 milliseconds and range is under 1ms 1ms AOC to over 20ms 20ms AF8 B BEACON Command to enter beacon text where up to 120 bytes of data and commands can be entered The data consists of character pairs lt CR gt and lt SPACE gt are permitted and the last character must be FF Data entry mode is terminated by the tilde character The message is permanently stored and the unit is reset on exit Fhhmmll FREQUENCY Set frequency to this value times the resolution The value hhmmll is a 24 bit binary number expressed as six hexadecimal characters 00 to FF H HELP Simple help message listing these commands also resets microcontroll
58. ill respond with the current settings The T and X settings are not reported Kiss Commands While you have the Terminal program operating with the Exciter you should explore KISS mode Sure you don t need to operate the Exciter in this way unless you actually enjoy hexadecimal numbers any more than you need to use KISS mode with a packet radio TNC but it is useful to have a play so that you understand how the ZL1BPU LF Exciter communicates All the computer programs that control the Exciter use these commands There are twelve commands which are summarized in the Appendix Let s look at them in detail To start with almost all of them provide a response the only exceptions are the and X commands Response is omitted here to allow for clean sending at the highest speeds for example ASK Morse at 30 WPM The computer programs can and do generally ignore the responses although they can be useful for checking that the command has been understood Some programs simply display the response without error checking The commands are all a single letter upper or lower case followed by zero to six other letters or numbers These are always hexadecimal i e 0 9 or A F or a f No other characters are accepted or needed and no Enter is needed although Enter CR and Linefeed LF are tolerated This is important because it allows the Exciter to operate over a packet radio link Unex
59. lows you to tune and test the Exciter 2 To compile a text file message into a beacon message which it then downloads to the Exciter message memory This message can include text as well as frequency mode speed and FSK shift commands 3 t allows the current parameters frequency mode speed and shift to be changed and when required to be permanently stored for instant start up when power is applied even without the computer connected Requirements As well as your ZL1BPU LF Exciter you will need a computer capable of running a DOS program with one serial port capable of operating at 19200 bps Most fast 486 or better computers would be appropriate but bear in mind it may also require to operate a sophisticated receive program at the same time You need an RS232 modem cable to connect the PC serial port to the Exciter User Manual Page 49 Any VGA monitor will do and memory and disc requirements are minimal The program will operate from a floppy disc just fine if the EXC SET setup file is also on the disc Using the Program Setup file The setup file EXC SET is shared with the more elaborate Exciter control program EXC EXE which is capable of real time programmed multi mode operation This file sets among other things the Exciter clock frequency and the PC serial port and baud rate These things need to be set before you run the program Just edit the file with a text editor making sure that the exact sa
60. me number of lines are left intact and that the values match those of your PC and Exciter The closer you can set the Exciter clock frequency typically 12800000 Hz the more accurately the programs will control the frequency settings of the Exciter synthesizer See the section on calibration earlier in this chapter EXC SET needs to reside in the same directory as the MAKEBCN EXE program and can be shared by both programs Using the Program The Immediate Commands When the program is running look closely at the menu commands on the right side of the screen The first set is operated by keys on the main keyboard and are immediate or program commands MAKEBCN 1 Ls lob A guste fes AJ Fi Beacon Off Fii TX ON Fi2 TX OFF Fig 8 1 The MAKEBCN screen User Manual Page 50 Report Sends a request to the Exciter for the current settings These are then displayed on the bottom line of the screen in typically cryptic Exciter hexadecimal This is a useful command to check that the Exciter is responding correctly to the computer program This is exactly the same as the Exciter R command S SAVE Instructs the Exciter to store the current parameters including the frequency mode speed and shift to be used when power is next applied to the Exciter If the mode set is MO the Exciter will simply operate as a carrier generator responding to manually sent commands If the mode is any other it will operate
61. nd mismatch overload The micro controller can be programmed and reprogrammed in circuit Modes ASK FSK DFSK MFSK IFK using Morse image or data Six beacon modes User Manual Page 69 10 Glossary ASCII ASK Baud Beacon DDS DFSK EEPROM Feld Hell Firmware FFT FSK Hexadecimal HEX ASCII IFK User Manual American Standard Code for Information Interchange The standard method for coding an alphabet of letters numbers and symbols in computers There are 128 characters in the alphabet Amplitude Shift Keying On Off keying as in Morse is the most common form of ASK The measure of speed of transmission of data events The baud rate is the speed at which the smallest entity of a transmission system a symbol is transmitted An automated transmission operated as a broadcast for test identification telemetry transmission and experimental purposes Direct Digital Synthesizer A frequency synthesis technique where the RF signal is directly generated by numerical methods Differential Frequency Shift Keying sometimes mis named DFCW method of sending Morse where dots and dashes are the same duration but on different frequencies Electrically Eraseable Programmable Read Only Memory A type of memory which retains stored values when power is removed An image mode where text is sent as dots like a dot matrix printer does Each column is scanned vertically bottom to top left to right Visible
62. ntiometer so you can adjust the power smoothly from full output down to virtually nothing The power amplifier behaviour includes an effective low pass filter so the power output and gain drop off quite quickly from 250 kHz upward To use the Exciter at the upper end of its range you will need to use the output direct from the D A converter which is flat from DC to 500 kHz and beyond There is sufficient output into a 50 Ohm load 50 mV RMS to drive an NE612 type mixer directly User Manual Page 16 4 Construction Not many parts are required and they should all be easily obtainable Most components are non critical so any available brand and many different styles of device would be quite suitable The parts list below specifies the parts used by the author but in reality just about anything will do The exceptions are e micro controller U2 must be the AT90S2313 10PC through hole or AT90S2313 10SC surface mount e amplifier U3 TDA7052A must be the A part the TDA7052 has insufficient frequency response The R 2R resistors R1 9 and R10 16 must be 1 The frequency reference X1 covered in Chapter 5 LF Exciter Parts List Copyright C 2002 M Greenman ZL1BPU Cct Ref Description Supplier PartNo Comment Mechanical Circuit Board Jaycar HP9552 93 x 140mm spot board Case DSE H2520 180x210 x 55mm two identical parts end panels supplied Knob To suit pot R40 Panel Overlays front and back Laser prin
63. o the beacon script User Manual Page 37 Syntax Pp The command turns on the output ports PD2 PD3 and PD4 according to the content of p Only the lowest three bits of p are significant so although values higher than 7 will work it is best to stay within the range 0 7 Outputs are standard CMOS logic outputs and can be used to control many things for example transmitter power level antenna switching or front panel LEDs PD2 corresponds to bit 0 to bit 1 and 4 to bit 2 Use the following table to set the outputs P binary PD4 PD2 0 000 OFF OFF OFF 1 001 OFF OFF ON 2 010 OFF ON OFF 3 011 OFF ON ON 4 100 ON OFF OFF 5 101 ON OFF ON 6 110 ON ON OFF 7 111 ON ON ON Table 7 2 Output port control R REPORT Syntax R A simple one line REPORT of the status of the Exciter It lists the current values for the A K M W and F commands S STORE Syntax S This command is used to STORE operating parameters in EEPROM so they are retained over power down When power is restored to the Exciter these default values are loaded before operation begins The values stored are FREQUENCY OFFSET MODE and KEY User Manual Page 38 the MODE stored is MO the Exciter will start as a conventional CW exciter with the key down If any other MODE is stored the Exciter will enter a beacon mode and start executing th
64. oadband transformer core Jarcar LO1234 Core TN25 15 or similar L1 Broadband transformer windings Pri 20T 0 7 mm Sec 22T tapped from halfway every 27 R27 R38 Resistor carbon film 0 25W 5 1k0 DSE R1074 R35 Resistor carbon film 0 25W 5 100k DSE R1124 R36 Resistor carbon film 0 25W 5 220k DSE R1132 R37 Resistor carbon film 0 25W 596 3k3 DSE R1086 R40 Pot panel mount carbon film MO linear Jaycar RP8524 U3 Amplifier BTL Audio 1W TDA7052A Philips Note must be the A part U4 Oscillator divider CMOS HEF4060 Philips Table 4 1 The Parts List User Manual Page 17 The circuit board is a perforated fibre board or glass filled project board with copper spots variously known as spot board matrix board or vector board The glass filled type with plated through holes is best It is equally possible to construct the unit on stripe board e g Veroboard but the layout is unlikely to be as compact It is best to choose a board and case that suit each other Layout is not critical and observing the author s layout in Fig 4 1 and Fig 4 2 will show that to a large extent the layout is suggested by the pin outs of the devices Use IC sockets for all ICs except the regulator U1 as this allows for easy repair following accidents and also reduces the risk of static damage during construction The micro fits in a standard 0 3 in pitch 20 pin IC socket E Fig 4 1 Inside view of the LF Excit
65. ode message by simply putting sections of message together one after another along with the necessary mode change commands With the correct commands any mode can follow any other mode with no interaction One way or another if your message contains more than just Morse and commands you will have to convert it to HEX and write it down Then with the message written out in HEX in front of you and the Exciter connected to a Terminal program and operating press B and start entering your message Once the message has been successfully entered enter FF as the last byte and send tilde to tell the recording process to quit You will very likely make a mess of it perhaps missing out one character or entering one twice so be patient and try again To quit the message enter and try again When you abort a partially written message the micro will reset so you need to press B again to start over You can type spaces or ENTER in the message and they will be ignored There is no way to see what you have recorded without sending the message via the beacon or using the ATMEL programming tools to peep inside the micro Sweep Generator Mode The Sweep Generator started life as a simple fixed rate 20 step sweeper as in the Signal Generator but it became apparent that at the cost of some minor complexity considerable versatility could be attained The Sweep Generator has four programmable properties th
66. ol e symbol rate timer sends the next beacon data bit and operates the script interpreter e sweep step timer steps the sweep frequency normally turned off Hexadecimal HEX counts 0 15 instead of 0 9 for each digit The numbers are represented by 0 9 and A and the hexadecimal digit is called a nibble A byte represents two nibbles and can express numbers from 0 2551 0 FFuex User Manual Page 13 This apparent program independence allows the operation to be very flexible for example you can change the frequency shift mode keying speed etc even while transmitting and also makes design of the micro controller firmware much more straightforward The Symbol Clock When the beacon is operating a slow timer at data symbol rate is required to trigger the next pass through the beacon control section of the firmware Each unique transmitted data event is called a symbol Between these events the micro controller is busy generating RF The timer could be generated inside the micro controller but unfortunately because of the very high crystal frequency it is not possible to directly generate long enough periods for the slower LF modes maximum would be about five seconds It is possible to extend the time by simply adding several of these periods together but it leaves unfortunate carrier interruptions whenever one of these events occurs As a result the signal has unwante
67. op of the column these can be used for graphics Each character will take several bytes to express from three for an I or T to five for W and more for graphics If each column is repeated several times the text slows but readability improves In Fig 5 1 four identical bytes were transmitted per column and the font used five active dots per column A simple font upper case only suitable for Feld Hell and MT Hell is included in the Appendix MT Hell can also be transmitted live from the EXC EXE program which uses advanced dot timing for higher speed and seven dots per column for better character shape see Fig 5 2 There is no compiler for JASON and there is not even a code table since the data transmitted is incremental and depends on what was transmitted before The best way to work out what needs to be loaded into the beacon for JASON mode is to use the I2PHD IK2CZL JASON V0 94 software set it in ZL1BPU format and have it transmit to another PC running a terminal program The software will transmit T followed by a series of Axx commands Type in the User Manual Page 25 message you need set the software in transmit mode and write down the values that appear on the other PC These are the values to program into the beacon just leave off the A Control functions can be added to the beacon message For example you can indicate the end of the message a change of keying mode
68. or other equipment required Morse and other ASK modes including QRS and QRSS FSK Morse DFSK Morse also known as DFCW MFSK single tone image modes such as Sequential MT Hell ASK image modes such as Feld Hell MFSK or IFK data modes such as JASON In fact multi mode and multi frequency messages can be used and the user can change the message any time even remotely using a PC or dumb terminal Using special PC software from the author or write your own the unit will also transmit many modes from the PC keyboard in real time It is also possible to define your own modes using a combination of frequency offset on off keying and keying speed The Exciter will generate User Manual Page 3 All the same modes as the beacon FSK and MFSK data including RTTY ASK data IFK data including JASON using I2PHD IK2CZL JASON V0 94 software Sweep Generation To use the Exciter for PSK modes will require an external modulator which could be conveniently interposed between the sine wave generator and the power amplifier Commands sent to the Exciter during PSK transmission will cause unwanted changes in transmitted phase The Exciter KISS protocol is packet ready so the Exciter can be operated remotely via a packet radio or other serial data link Beacon Operation To operate the ZL7BPU LF Exciter as a beacon you will need e AnLF antenna and tuner well of course e 12 DC power source capable of 20
69. pected or misunderstood information results in the Exciter sending a response This occurs with Enter as well but has no effect on operation except that a partially entered command will be abandoned Enter is therefore useful for terminating commands entered in error Before the commands are studied in detail it is important to understand the concept of resolution steps As discussed earlier the basic resolution of the ZL1BPU LF Exciter is dependent on the crystal used It s typically about 1 12 Hz and when any of the following commands that relate to frequency are used it is steps of this size the resolution steps that are implied Every value entered represents a number of resolution steps so the frequency or frequency increment that results will be the number entered multiplied by the resolution User Manual Page 32 Syntax Axx ADD an offset of xx resolution steps where xx is 00 to FF in two hexadecimal characters The offset is not cumulative so adding another offset adds to the base frequency not the current offset frequency This command can be used in conjunction with T and X to generate ASK FSK and MFSK transmissions in a wide variety of modes The command has no useful effect on ASK modes such as MODE 1 ASK Morse and MODE 5 ASK HELL or on MODE 6 MFSK IFK mode where offsets are set directly from data In Sweep Generator mode ADD sets the sweep dwell time time per step The re
70. quite so straightforward To generate messages manually which is the only way at present for graphics messages it is best to work out and write down the message first Simply write the bytes as pairs of characters separated by spaces Don t put too many on each line say eight pairs as it is easy to lose your place when typing them in Messages that contain only commands and Morse can be made and downloaded directly by MAKEBCN but other modes require more ingenuity You can store the message in a file then download the file you create using a Terminal program but there must be some way to send the message slowly such as a pacing option as the micro is not capable of receiving and storing messages any faster than about 100 bytes second the EEPROM write process is slow Enter the commands as described in the section above and the Morse data from the table in the Appendix Graphics for MT Hell Mode 4 and Feld Hell Mode 5 come from the font table in the Appendix Each character consists of several bytes and note that some characters require more bytes than others because the font is proportional different widths for different characters The best way to work out a JASON message Mode 6 is to use the JASON software by I2PHD and IK2CZL to create it for you The process was discussed under Beacon Message in Chapter 5 You can also do the same for Hell modes using EXC EXE User Manual Page 43 You can make a multi m
71. ransformer is not grounded except at the front panel used single sided PC board for the front and back panels Checkout Before applying power check the board for shorts between the power rails using an Ohm meter Apply power before fitting the socketed devices and check for 5V 12V and ground at the correct pins Next fit the 4060 device U4 and check that it oscillates about 256 Hz on the test point on pin 7 Now fit the micro controller U2 and check that it does not get warm It won t run of course until you have programmed it Then program the device see below and using an oscilloscope or spectrum analyser if you are lucky enough to have one of these marvel at the signal at the point marked DDS OUT This is the synthesized LF signal a 256 discrete point sine wave sampled at 1 3 MHz When you are marvelling at the waveform remember that all the 256 points do not appear in every sine wave cycle If you have used a 12 800 MHz crystal the unit should run correctly as soon as it s programmed The output should be around 180 kHz but the exact frequency won t matter as calibration takes place in the PC software Other crystal frequencies will necessitate one small change to the micro controller stored values This is covered below under programming To check out the RS232 port connect it up to a PC communications port set to 9600 bps the Exciter s default value Run some terminal software such as Windows Terminal W
72. rosoft Word and ported to PDF format for distribution 2H bpu nzart org nz User Manual Page 2 1 Introduction The ZL1BPU LF Exciter is an advanced unit out performing many conventional LF Exciters of the crystal controlled VFO or PLL synthesis varieties Despite the performance advantages and its versatility the unit is inexpensive simple to build has no adjustments and is mostly easy to use The frequency reference for the unit is derived from a single stable high frequency crystal or TCXO temperature controlled crystal oscillator and therefore the transmissions are extremely stable Because the unit uses a direct digital synthesis technique the LF signals are also very clean It is especially important in equipment for narrow band transmissions that associated carrier phase noise is very low The unit is self contained 12V DC operated and generates about 1W sine wave output from 10kHz to at least 250 kHz and is useful from 7 kHz to 400 kHz in steps of 0 085 Hz Power level is DC adjustable over at least 60dB range This feature plus the built in sweep generator makes the unit a highly useful signal generator Without the power amplifier the output is 50 RMS into 50 Ohm from zero to 400 kHz The ZL1BPU LF Exciter can be externally set up and controlled by a computer or terminal and has a built in beacon system The unit will transmit any or all of the following modes using the built in beacon with no PC
73. sed by the program to identify the end of the message This allows you to add other text and comments later on in the file that are not converted into the message Here is an example of a simple message text file for use with MAKEBCN Note that the end of line Enter characters are converted to spaces SM1SF22CE6ESK0006 QRP BEACON DE ZLIBPU 711 RF72KU AR SM3SA7ESKOOCO ZLIBPU In this example once the script is downloaded and the beacon started it first sets the mode to ASK M1 the frequency F22CE6E the keying speed to about 12 WPM K0006 sends an ID message then changes to DFSK mode M3 10 Hz shift A7E three second dots K00CO and sends my callsign Finally the command is terminated and will repeat from the start The program automatically stores a final terminator in the Exciter memory which forces the beacon to start again at the beginning of the message User Manual Page 55 Unless the message text file is in the same directory as the MAKEBCN EXE executable when the F9 SCRIPT command asks for a file name you will need to specify the exact and complete path to the text file in addition to its name Other Features The program reports all commands at the bottom of the screen It also continually monitors responses from the Exciter and will display them in a long line at the bottom of the screen The responses are not error checked or interpreted in any way by the program
74. ses function keys for commands leaving most of the keyboard free for real time typing The commands are F1 Increase power F2 Decrease power F3 Increase frequency fine mHz resolution F4 Decrease frequency fine mHz resolution F5 Decrease frequency 10 kHz F6 Decrease frequency 100 Hz F7 Increase frequency 100 Hz F8 Increase frequency 10 kHz F9 Step to next mode default is first in list F10 Step to next message source default is keyboard F11 TX on F12 TX off ESC Closes the program Note F1 and F2 only work if the output ports PD2 and PD4 are wired to an R 2R network to control the amplifier gain See the PORT command under KISS commands in Chapter 7 This program is not intended to provide real time control of the output ports If you change mode in the middle of a message or with text in the keyboard buffer nothing nasty will happen but there may be partial characters transmitted in the new or old mode Similarly if you change messages slowly there may be partial messages sent the first character of each message The messages always start at the beginning In this sense the keyboard buffer is no different to the fixed messages It is a good idea to include a space in the fixed messages to force a silent period at the message start WinEXC This program created by and available from Con Wassilief ZL2AFP seeks to replicate the operation of EXC but in a true Windows environment As you can see in F
75. solution is about 1 12 milliseconds and range is under 1ms 1 AOC to over 20ms 20ms AF8 See the comments about Sweep Generator mode under the K command B BEACON Syntax B xx xx xx FF Enter a new BEACON message The command is used to enter beacon data representing text and graphics This becomes the beacon script and the content of the data depends on the mode to be transmitted Up to 120 bytes of data and commands can be entered The data consists of HEX ASCII character pairs CR and SPACE are permitted but not stored and the last character pair must be FF Data entry mode is terminated by the tilde character The message is permanently stored and the unit is reset on exit Four types of information are used to create a message These are a Morse text coded in Murphy format b bit map information for graphics modes c differential frequency offset data for JASON mode or offset data for MFSK and FSK modes and d embedded script commands which allow the beacon to change mode and various other parameters during the message These four types of information are covered later in the chapter User Manual Page 33 F FREQUENCY Syntax Fhhmmll Set the Exciter transmit FREQUENCY to this value times the resolution The value hhmmll is a 24 bit binary number expressed as six hexadecimal characters 000000 to FFFFFF The useful range is 000001 about 1 12 Hz to 480000 about 400 kHz
76. t control software is used since the serial commands are different Sweep Generator The ZL1BPU LF Exciter uses a direct digital synthesis technique realised in software and so the frequency generated can be changed virtually instantly The sweep step duration frequency step and number of steps are all programmable In the sweep generator mode an internal timer changes the frequency for example every 5ms with typically 20 steps per sweep and generates precise frequency steps appropriately timed for use with an oscilloscope The sweep generator includes a SYNC output that is high only during the first frequency step This is used as a synchronizing signal for the oscilloscope With the time base of the oscilloscope set to for example 10ms div the display conveniently shows two frequency steps per division The sweep generator can sweep a range greater than 100 kHz and operates over the full range of the generator The minimum step size is 85 mHz and the maximum about 5 5 kHz These features make the unit very handy for checking out antennas tuners and even sweep IF filters you can sweep in precise steps and just about reach 455 kHz Because the sweep can go from zero it is also useful as an audio sweep generator so you can sweep audio amplifiers filters and SSB transmitters The sweep step resolution is the same as the frequency setting resolution There can be from one sweep off to 255 steps and the sweep dwell time tim
77. t to the Exciter and converting this value back to decimal In this way the frequency accurately reflects the digitization limitations of the Exciter Below in the row starting with the Copyright message is the range statement This gives the operating frequency range of the software and Exciter the upper limit depends on the crystal frequency set in EXC SET Below this line is the current data sent to the Exciter To the right side of this line is a small buffer which shows the last 22 or so characters sent to the Exciter User Manual Page 58 At the bottom in the box is the keyboard buffer This is where you type text to be sent The program features KOX Keyboard Operated Xmit so the transmitter goes on and starts sending as soon as you start typing The transmitter goes off back to receive when the keyboard buffer becomes empty Below that again is a list of the function keys The program contains no graphics so will operate in a Windows DOS box This is handy as it allows you to run ARGO at the same time to monitor your transmissions or to receive during a QSO Just remember to return focus to the EXC program by clicking on its window with the mouse in order to start typing and transmitting again Keyboard 181 400 06 12 BPU CQ de ZLIBPU ZL1BPU ZLIBPU RF72ku TEST ZL1BPU MURR10 Fig 8 2 The EXC screen User Manual Page 59 Using the Program Commands The program u
78. ted and laminated Sheet 1 C1 C5 100nF mono ceramic 50V DSE R2001 C2 C3 21 or 33pF NPO ceramic 50V Jaycar RC5317 C2 can be adjusted for exact frequency trim C4 100pF polystyrene 250V DSE R2819 C6 C8 10uF 25V Al electro radial DSE R4315 C9 10uF 16V electro Jaycar RE6066 D1 D2 Diode Si signal 1N4148 Jaycar ZR1100 J1 Header 2 54mm pitch 2 x 5 pins snapoff DSE P2728 J Tag programming connector J2 RS232 connector DB9F panel mount Jaycar PS50804 R1 R9 Resistor metal film O 5W 1 2k00 Jaycar RR0579 9reqd R10 R16 Resistor metal film O 5W 1 1k00 Jaycar RR0572 7reqd R20 R24 Resistor carbon film 0 25W 5 1k0 DSE R1074 R21 R23 Resistor carbon film 0 25W 5 4 7 DSE R1090 R22 Resistor carbon film 0 25W 5 100R DSE R1050 R25 R26 Resistor carbon film 0 25wW 5 10k DSE R1098 R29 R31 Resistor carbon film 0 25W 5 10k DSE R1098 U1 5V regulator low power 78L05 DSE 26108 U2 Microcontroller 9052313 10 Atmel Try Apex Electronics Memec or www polykom com au a Crystal 10 to 16 MHz 12 MHz preferred Good quality high stability crystal or use TCXO C12 C14 0 47uF 50V mylar or polyester DSE R2130 C13 220uF 25V Al electro radial DSE R4390 C15 1nF 50V mylar or polyester DSE R2010 D3 Diode power 1N4002 1N4004 Jaycar ZR1004 D4 LED 5mm red DSE 24085 05 LED 5mm green DSE 24087 J3 Coaxial DC power connector 2 1mm panel Farnell 299 972 J4 J5 BNC connector female panel screw thread Jarcar PS0658 L1 Br
79. tionality so the following comments also apply to it Requirements The requirements are the same as for The same setup file EXC SET is used WinEXC also uses the EXC SET file Modes are defined in the file along with the pre defined messages Using the Program Setup file Most of the setup file the first five lines is exactly the same as for MAKEBCN What s different is the pre definition section that follows There are 10 pre defined modes which you can alter if you wish There must be always 10 mode lines Each line contains the name of the mode the modulator to use the frequency offset to use and the keying speed as follows MODE NAME MODULATOR OFFSET SPEED The mode name must be in quotes and be 8 characters or less The modulators are referred to by a number MOD in the table below MOD KEYING CODE COMMENT 0 ASK MORSE Conventional on off keyed Morse 1 FSK MORSE FSK Morse keydown is shifted up 2 DFSK MORSE Dual shift Morse dash is shifted up 3 MT HELL GRAPHIC Multi tone Hellschreiber 4 MFSK ITA2 MURRAY visually decoded MFSK Table 8 2 EXC s Modulators User Manual Page 57 OFFSET is the number of DDS resolution steps FSK shift or per MFSK step SPEED is the number of seconds per symbol per data bit or dot although MFSK modes use much smaller dots for the same FFT receiver speed say one third to one quarter and are therefore less sensitiv
80. unications with device to be programmed This message also appears if you have selected the wrong device in the Project Manager everything worked fine you are in a position to try programming The software implicitly loads files into the current window so in order to load the executable firmware select the Program Memory window by clicking on it or from the menu Window Program Memory Next select File Load and locate and select the executable file EXC_Dnn HEX The file is in Intel HEX format You are now ready to program the device From the menu select Program Erase to erase the device then Program Program Device to program it It should take 10 20 seconds depending on the speed of your computer If the device is faulty or not blank it may take longer and will report errors User Manual Page 30 At this point the micro starts talking to the serial port and you should see a line of garble on the Terminal screen If you wish to try the demonstration message select the EEPROM Data Memory window menu Window EEPROM Data Memory Select File Load and locate and select the EEPROM file supplied EXC_Dnn EEP From the menu select Program Program EEPROM to load the message It should take just a couple of seconds If you are using a 12 7 or 12 8 Mhz crystal you will immediately see the Exciter start up message appear on the Terminal screen a couple of times The final step applies if you are using a
81. ut of course they do use up message space Here is an example that sets the equivalent to KISS commands A08 K00CO M2 FD 08 FE 00 CO F2 The commands consist of a command byte which will contain the command followed by zero to three data bytes The commands always start with F and so values of message data starting with F are not permitted where they might be interpreted as a command this has not proved to be a disadvantage Commands that are misunderstood are ignored but be aware that following data belonging to a misunderstood command may well be processed as other commands or message data There is great potential for getting strange results but a quick check of the data from the point where the message goes crazy will usually pin point the problem There is a list of sample script data in the Appendix The script commands are described below in hexadecimal format where two hex characters represent each byte User Manual Page 41 MODE Syntax Fn This is a family of six commands F1 to F6 These commands set the beacon mode to n where has the same meaning as the KISS MODE command is not used as this would turn off the beacon and defeat further script processing Using these commands you can switch modes in the middle of a beacon message It will generally be necessary to follow mode commands with changes to SHIFT and SPEED PORT Syntax FB pp Sets the three output ports PD2 PD3 and PD4 according to the
82. utput but very good band pass filters are necessary to exclude other frequencies and this technique does not suit broadband operation for which this Exciter was designed Another interesting thing to try is to give the Exciter negative frequency values The frequency value Value to Add in Fig 3 1 is a 24 bit number 0 to 16777215 and all the numbers above 8388607 represent negative frequencies For example a value of 16777215 will generate the same frequency as a value of 1 but the look up table will be stepped backwards This has no effect with a sine wave which is of course symmetrical but has a dramatic effect on ramp waveforms Another odd thing about negative frequencies is that FSK shifts are reversed and in sweep generator mode it is possible to sweep backwards or even through zero User Manual Page 11 Frequency Resolution Mathematics The DDS technique used in the ZL7BPU LF Exciter is borrowed from a signal generator by Jesper Hansen This highly efficient but tiny piece of software only six instructions performs the high speed adder and look up table functions in only nine micro controller clock cycles In the Exciter the micro controller clock frequency is very high typically 12 8 MHz and so the DDS executes one step every nine clock cycles or at a rate of 12 8 MHz 9 1 42 MHz The frequency resolution is also related to the size of the phase accumulator register The Exciter uses a 24 bit register an
83. utput is a clean sine wave with very low harmonic content To operate a linear amplifier simply connect the output to the transmitter input set the output tap for 50 Ohm operation and adjust the front panel output level control for sufficient drive It is a good idea to include a high Q matching circuit between the Exciter and the transmitter to further attenuate spurious products such as the second and third harmonic and the sampling clock frequency However given the operating bandwidth of most transmitting antennas this will usually be quite unnecessary To operate a transmitter that requires square wave or twice frequency drive add the necessary squarer and diver circuitry to the output of the sine wave generator and omit the 1W power amplifier CMOS level 5V square wave drive is also available from the micro controller at PB7 pin 19 or from programming header J1 You will definitely require a low pass filter on the transmitter output if you use square wave drive Real time operation requires keyboard control The Exciter is connected via a serial control link to a PC or other computer which runs a keyboard control program such as the authors EXC EXE or Con ZL2AFP s simple Windows program These programs send the necessary KISS commands to set the transmitted frequency turn the transmitter on and off and generate the on air signals They also allow you to change mode and send from the keyboard or from pre programmed messages Suc
84. value should be 160432110 Now that s 187 1 How do we know The simplest way is to use a Windows calculator or other calculator with a hexadecimal mode Perform the calculation in decimal and simply press the HEX button to convert the result so that s the value to send the Exciter using the KISS F command F187AE1 F commands always have six following characters We only need worry about hexadecimal numbers when entering frequencies manually The PC software does all the hard work for you calculating the numbers and converting to hexadecimal The Micro Controller This is the heart of the Exciter As well as providing the DDS functions described above the micro controller has software to record messages interpret commands and control the DDS output However it cannot do all these things at once and specifically it cannot communicate with the user receive commands send data while generating LF signals So you will notice that while you talk to it the carrier generation stops This is most obvious when controlling the unit manually as the commands sent from a PC program are very brief and those generated by the internal beacon and sweep generator are even briefer In effect there are four main sections of program all apparently working independently which make up the Exciter controller e DDS synthesizer generates the signal e The serial port command interpreter operates the KISS protoc
85. y contain one or more or even fractional parts of bits of digital information See baud Temperature Compensated Crystal Oscillator An inexpensive but high performance type of crystal frequency reference Temperature variations in the crystal are compensated electrically rather than eliminated by close temperature control Universal Asynchronous Receiver Transmitter A device in a computer designed to transmit and receive asynchronous stop start serial data Page 71 DDS LF EXCITER SCHEMATIC 45V Sheet 1 of 2 F200 Tx ED 0 PDO 2 C6 40uF PD 3 25 11 02 R25 10k R26 100nF 1N4148 ok AT90S 2313 10PC RESET 1 PE 19 B PD2 18 7 PDS 17 DOT 8 PD4 PBA 16 8 PD5 PB3 15 PB2 14 13 12 GND X1 X2 For Ext Reference omit C2 am 6 J2 DB9 F and 1 EXT REF can be 10 16 MHz 12 800 MHz preferred 1 12 000 nae EXT 0 c2 27 pF C3 27 pF X1 can be 10 12 or 16 MHz PROGRAM HEADER Copyright 2002 Murray Greenman ZL1BPU Page 72 User Manual J3 DDS LF EXCITER SCHEMATIC gt H2 Sheet 2 of 2 T TXLED 03 144002 Uu pst D4 RED LED C13 220uF 25V i ur Mak RUN AF DC SUPPLY 05 GREEN LED INPUT 35V C15 1nF SOV mylar 9 IB Va TP 255Hz 10 Re 03 0 SYNC OUTPUT 05 4 SYNC MBpa QUT J4 adi d R37 1 AMPLI

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