TS-790 & 9600 Baud Operation (Rev 2) ---------------------------- These mods are working very well with 9600 bps UO-14 . currently used at my site. TS-790 ; FM Direct from Discriminator ------------------------------------- Detected and amplified/buffered FM direct from the receiver discriminator is available from Pin-9 IC1 (Sub) or IC8 (Main) located on your IF UNIT pc board located under the bottom cover of the radio . Look at the IF UNIT schematic to find the proper points. I use IC1 (Sub) for reception of uo14 downlink and IC8 (Main) for terrestrial 9600baud operation on a simplex frequency. I run both discriminator connections to a switch located on my tnc so I can select either one. I installed 2 RCA phono jacks on the rear blank panel of the radio for my mic UP & DOWN connections along with a 5 pin din jack on that same panel wired as per standard tnc signal connections, only it is used for my 9600 baud tnc exclusively. The rear panel I'm talking about is the panel which is installed where the 1.2Ghz module would go... I used RG/174 mini coax for ALL connections internally in the radio and externaly between the radio and tnc.. TS-790 ; Direct varactor FM Modulation -------------------------------------- Inject your TX audio at the cathode side of diode D81 with a 1K ohm resistor in series. You can find D81 near Q73 on your IF UNIT pc board located under the bottom cover. Set MODEM deviation for approx 3Khz on the air. You will also want to install a switch on your tnc to OPEN the xmit audio line so you can use the radio in normal voice mode with the tnc still switched on as the modem xmit audio is NOT MUTED at all. Misc ; ------ Use a low wattage soldering pencil with a small tip to make connections. Carefully adjust the TX audio level by VR1 of the modem, it's rather low. You would probablly need some local friend to do this adjustment, asking him to tell you when his 9600 baud TNC's DCD LED stays steady (no flicker) or if you have a commercial two way radio station monitor available, check the deviation with that, oooorrrrr, lacking any other way , try to connect to uo14 and starting with the modem xmit audio level of 0, turn the modem audio output up slowly until you get SOLID CONNECTS an ACKS EVERYTIME. A TXDELAY of approximately 150 milliseconds should work ok, there is no need to make the TXDELAY ANY LONGER THAN NESSARY.. Terrestrialy I can set my TXDELAY down to 5 (50ms) and still have no problem connecting to my high speed node which uses a Kantronics DVR-2 radio.. ******************************************************************************* TS-790A AUTOMATIC DOPPLER FREQUENCY COMPENSATION CIRCUIT FOR 70cm DOWNLINK . THE CIRCUIT LISTED BELOW IS A MODIFICATION OF THE ORIGINAL JA6FTL TS-790 AFC CIRCUIT DOWNLOADED FROM UO14 AND NOW MODIFIED BY KF4WQ TO INCLUDE DOPPLER SHIFT TRACKING (UP FREQUENCY) TO RECOVER FROM OVER COMPENSATION OF DOWN BUTTON ACTIVATION.. ESSENTIALLY THE ADDITIONAL CIRCUIT LOCKS OUT "DOWN" FREQUENCY COMPENSATION WHILE "UP" FREQUENCY DOPPLER COMPENSATION TAKES PLACE & VISA-VERSA ... (THE TS-790 TRANSMITTER WAS CAUSEING THE "ORIGINAL" AFC CIRCUIT TO ACTIVATE REPEATEDLY EVERY TIME THE PTT LINE WAS KEYED WHILE UPLOADING OR REQUESTING FILES & HOLES IN PB.) THE RECEIVED DOWNLINK FREQUENCY WOULD EVENTUALLY BE PULLED TOO FAR OFF FREQUENCY TO ALLOW DECODING OF THE SIGNAL, ESPECIALLY ON LONG UPLOADS. EVEN THOUGH THE DCD LINE STILL INDICATED A VALID FSK SIGNAL BEING RECEIVED. THE DCD SIGNAL HAS A BROAD "WINDOW" FOR LOCK INDICATION. SO EVEN THOUGH THE DCD SHOWED A VALID SIGNAL COMING IN, THE "DECODING WINDOW" WAS IN FACT OF A NARROWER RANGE THAN INDICATED BY THE DCD LITE. I WAS MANUALLY BUMPING THE FREQUENY DIAL BACK UP FREQUENCY A COUPLE OF HUNDRED Hz. TO GET BACK INTO THE FREQUENCY RANGE WHERE DECODING OCCURS, BUT THIS HAS BECOME TOO MUCH OF A BOTHER..THE RESULT OF THIS PROBLEM IS THE CIRCUIT SHOWN BELOW. BOTH W3QNS AND MYSELF HAVE TS-790A's AND NOTICED THIS ANOMALY. IT DOESN'T SEEM TO MAKE MUCH DIFFERENCE WHAT POWER SETTING IS USED EITHER. IN EITHER CASE THE PROBLEM WAS SOLVED WITH THE CIRCUIT SHOWN BELOW. Auto UO-14 RX frequency tracking for TS-790A or FT-726R ------------------------------------------------------ The doppler shift range in overhead pass reaches to 20kHz. It is essential to tune-in RX frequency for good through put. I assembled auto freq. tracking for UO-14 FSK signal reception and achieved good results. ******************************************************************************* [Original JA6FTL AFC Block diagram] RX discri.out<-- voltage comparater--INV--NOR--switching TR---> Down control (Q1) (Q2) (Q2) (Q3) | G3RUH board DCD ----------------------- ******************************************************************************* [Modified JA6FTL AFC Circuit by KF4WQ.] GND Q1:LM324 or TL084 Q2:74HC02 Q3 & Q4:2SC945 etc. | or 74LS02 or 2N2222 etc. (C:0.01) | ---- ----- ---- ---- *a<-(R:1M)--------3 Q1 1-----6 Q2 4 ----3 Q2 1---(R:470)---B Q3 C---> DWN *c +12V--(R:8k)--- 2 | | -5 | --2 | | --E | | ---- | | ----- | ---- | | ---- | | | | | | (VR:10K POT.) | | | | | | | | | | GND GND | GND | | | | | D1 (1n914) | | |------->|----------> DWN *e | | + | | | | D2 (1n914) | | |------>|-----------------> UP *f | | | + | ---- | | ---- ----8 Q2 10--------(R:470)-------B Q4 C----> UP *d ----9 | --E | | ---- | ---- | | *b<-- G3RUH board DCD line-- GND GND +12V +5V Q1 11 4 Q2 7 14 NOTES: *a: to RX discri out (=G3RUH board RX IN) *b: to G3RUH board DCD line (U10 pin 13) *c: to down control pin of mic terminal (TS-790 mic pin 3) *d: to up control pin of mic terminal (TS-790 mic pin 4) *e: to down control pin of mic jack (FT-726) Q3 not used *f: to up control pin of mic jack (FT-726) Q4 not used setting of VR:10k The discriminator IC output level is 5.8V +-2V. With NO RX signal, set the VR so that Q1 pin 1 level is at the threshold point where the signal level turns from HIGH->LOW. This level is an analoge voltage and can be read with a standard volt/ohm meter. You will notice that the discriminator noise constantly tries to affect this level but it won't, because the logic circuits only key when there is a DCD signal to ENABLE the circuit. In my case, I assembled the circuit on a small (1.5"x1.75") universal PCB and put it into the PAC-COMM TNC-200 along with the NB96 modem board. All power and signal connections are made to the nb96 modem board with the exception of both mic. UP & DOWN control lines which goto the rear panel RCA phono jacks on the radio. When the circuit is working properly you will find that the UP & DOWN control lines are constantly toggleing while the satellite is sending at 9600 baud. You will also notice that the overall effect is to keep the downlink frequency locked to within +/- 100Hz of the incomming signal which is easily well within the range nessary to decode the downlink.. I have found that even if you are initialy off frequency by as much as 10Khz, the circuit will detect the presence of the 9600 baud signal and begin to pull the radio to center frequency.. This pulling effect increases as your dial frequencey gets closer to center frequency until you will see that the dial frequency then just jitters +/- 100Hz of center frequency. If the constant beeping troubles you just turn the beep OFF in the radio. Remember this is a completely solid state radio with no moving parts to ware out so don't worry about the continual jittering obout the center frequency.. ******************************************************************************* LOGIC TABLE DCD Q1 Q2 Q2 Q2 Q3 Q4 LINE PIN 1 PIN 4 PIN 10 PIN 1 COL. COL. NO REC. SIGNAL HI LO HI LO LO HI HI ^ ^ | | NO DOPPLER CORRECTION SIG-TOO HIGH LO HI LO LO HI LO HI ^ | ACTIVATE DOWN BUTTON SIG-TOO LOW LO LO HI HI LO HI LO ^ | ACTIVATE UP BUTTON Don't worry about traking the "UPLINK", the bird has afc on the uplink. ******************************************************************************* The following information is included to allow operation of the TS-790 for terrestrial use also. You will probably find the need to switch the above circuit off line while operating 9600 baud terrestrialy or just plain voice operation because the afc is ment for full duplex operation so when it hears a signal it pulls frequency , this would be catastropic when operating simplex or when using voice as it might just decide to change frequency just when you dont want it to... Also you will want to disable the modems transmit audio line because it is ALWAYS ACTIVE and would therfore cause great distress when the radio is being used for voice communication. If you are going to ALSO use the radio for simplex 9600 baud work then you will want the ability to select either (SUB) or (MAIN) reciever discriminator audio lines.. What this all boils down to is additional subminiature switches used to control all these functions. I have 3 additional switchs on the front panel of my pac-comm tnc 200, one of which is a double poll/double throw switch that opens the +5volt line going to the afc circuit board and selects 9600 baud terminal baud rate for terrestrial use in one position while in the other position it applys +5 volts to the afc pc-board and selects 19.2kb for the terminal baud rate used in satellite work.. I also have a separate spst miniature switch to open the modem xmit audio line, and yet another spdt switch to select between sub and main reciever audio lines.. YES my tnc front panel is quite crowded but I have full control of things from that point. 73s RICK ( KF4WQ ) /EX