PAC-COMM TNC-220 9600 baud Fullduplex by G4WFQ
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For those of you owning a 220 and would like to be able to operate at
9600 fullduplex the following information will save you an awful lot of
hassle and bother.

If you thought it did work at 9600 fullduplex think again it doesnt. The
manual does say it can, but dont believe a word in the manual its all a load
of rubbish. Same goes for what it says about the Watch dog Timer.

Carry out this simple mod, should take you all of 5 minutes.
It took me 3 days to figure out why I could not Digi-peat via UOSAT3 at
9600 bauds. Its because when you turn Fullduplex on the TX Radio baud rate
returns to 1200 buads whilst the rx baud rate remains at 9600. Most strange
isnt it. Pac-comm told me it does work. Cant see how myself.

Locate 74HC4020 (Baud rate generator chip) and remove from SKT
Bend pin 12 up and replace.
Solder flying lead onto pin 12.     (DONT FORGET THE HEAT SINKS)
Solder flying lead onto pin 1.      (  "    "     "    "    "  )

Terminate these two leads onto a SPDT switch.
Solder lead from output of switch to pin 12 (rtxca) of 8530 sio chip.

Throw the switch for 9600 fullduplex. Restore for 1200 operation.

Thats it job done.

Pac-Comm were there usual selves in support of this problem. NILLLLL.

73 de Dave G4WFQ @ GB7HXA 5 NOV 90 2330UTC
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