IC-275/IC-475 MODIFICATION FOR SATELLITE PACKET OPERATION Here is the way I cabled out the IC-475 & IC-275 rigs for 1200 bps and 9600 bps. All I have to do is turn off the unwanted TNC. You can't leave both of them on or you will transmit both audios at the same time. The color codes are for my own use to remind me of the color codes in my own cables. The AQS and ACC are the sockets on the rear of the sets. BE CAREFUL OF AQS PIN 13 AND ACC(1) PIN 7. They carry 13.8 volts and can damage things if accidentally shorted to other pins! I cut them off on the solder side of my cable plugs. By the way it will be necessary to disable the beep tone that occurs when you depress a key on the IC-475. The beep tone is sent through the speaker system and will interfere with the 1200 bps data signal otherwise. The beep tone is disabled by rotating R348 (Beep Sound Level Adjustment) counter clockwise. See Section 9, p42 of the users instruction manual for a photo. In my IC-475, I have also changed out the FL4 (Muratta CFW455-E) for a wider filter. The CFW455-E is a +/- 7.5kHz (15kHZ) filter. I first tried using a CFW455-D, a +/- 10.0kHZ (20kHz) filter with a definitely noticable, but not terrific improvement. I then changed out this filter for a SFH455-D Gaussian shape filter designed for data reception. There seems to be a further small improvement with this filter but not such that I can place numbers on it. In addition the S-Meter must be recalibrated if you want it to read correctly with this last filter. It reads low. I think the CFW455-D is the way to go and still have the S-Meter still behave. 73, Roy -- W0SL CABLE PINOUTS AND COLOR CODE TNC-200 TO IC-475 & IC-275 FOR 9600 BPS OPERATION FUNCTION TNC RADIO PORT IC-475 AQS IC-275 AQS COLOR TX AUDIO 1 - 2 ## RED GROUND 2 9 - BROWN 2 - 1 GREY PTT 3 - 7 YELLOW RX AUDIO 4 5 # - GREEN RF DCD 5 - - - # Existing shielded lead to AQS socket pin 5 is re-terminated inside IC-475 to IC6 pin 9 through 5 to 10 mfd non-polarized capacitor. This lead is labeled AQAO on plug P13 on IC-475 schematic and can be removed easily from plug housing by CAREFULLY, slightly lifting plastic retaining tab on the side of P13. IC6 pin 9 is available on a bare wire between P13 and IC6 (they are about 1 1/2 inch apart). It comes out on the component side of the board, goes about 1/2 inch and goes back in the board. It is easier to solder the capacitor to this bare wire than the IC itself and much more desirable I think. The other capacitor lead is slipped into the female P13 sleeve just removed from P13. Nothing is cut! The bottom of the rig is removed to get access to P13 and IC6. ## Transmit audio can be input on AQS socket pin 2 without mods. It goes to P12 on lead AQTN and drives Q33 through trim pot R152. Q33 provides plenty of gain to modulate the rig and doesn't seem to distort the transmit audio. You can adjust the transmit gain either in the modem or by using R152. I use R152 because I use the modem to drive both the IC-275 on UO14 and the IC-475 on local 9600bps packet. That way I can independently set the transmit audio level for both rigs and switch it between them. DIN PLUG PIN LOCATIONS AS SEEN FROM BACK OF PLUG TNC RADIO PORT IC-475/275 AQS PORT 3 1 X X 2 1 5 4 X 7 X 5 2 X X X 9 X CABLE PINOUTS AND COLOR CODE TAPR PSK MODEM TO IC-475 & IC-275 FOR 1200BPS OPERATION WITH AO16 AND LO19 FUNCTION PSK MODEM PORT IC-475 ACC(1) IC-275 ACC(1) COLOR UP/DOWN UHF 5 1 * - WHITE GROUND UHF 2 & 1 2 - BLACK VHF 2 - 2 BROWN PTT VHF 3 - 3 YELLOW TX AUDIO VHF 1 - 4 RED RCV AUDIO UHF 4 5 - GREEN VHF 4 - 5 GREEN PSK MODEM PORT IC-475/275 ACC(1) PORT 3 1 X X 5 4 3 X 1 2 5 4 2 * Wired added from mic connector pin 3 to ACC(1) pin 1 in IC-475. The mic connector pin 3 is available on a small circuit board immediately behind the mic socket. The socket is wired to this board via a small ribbon cable. ACC(1) pin 1 is not connected to anything, so the new wire must be soldered directly to pin 1 on the back of ACC(1). Fortunately it is on the side of the socket nearest the side of the rig and accessible with a bit of care. This wire is necessary only if you don't want to access it through the mic socket. I like all my cables on the rear of the set. Also, this wire is needed only if you are using the PSK modem UP/DOWN pulsing capability to keep your rig tuned into the downlink signals.