High baudrates on TAPR TNC2 clones
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About a year ago a bulletin was passed around about changing one of the IC's in a TAPR 2 TNC (or clone) which would allow it to utilize a Computer/TNC baud rate of 9600. I never felt that this high of a speed was necessary especially on HF packet. Not so, over the past few months I have had problems with one task locking my system up. Also others such as Mike KA3NVP have had the same problem. We were blaming it on the software as we both changed over to the (W0RLI 9.xx) and never had problems before.

After much hair pulling and sending "nasty-grams" to Hank (RLI) I found the problem. It was RF getting into the TNC! Well, many hours of shielding, bypassing, grounding and  general cleaning up did not solve the problem. I would put the software into the local "cmd:" mode, key the transmitter and tap the return. This should have given many "cmd:" prompts but things would just sit and do nothing until the transmitter was unkeyed. This told me the computer and TNC could not talk to one another when the rig was in the transmit position. Ah, the lockup was because only part of the command was getting through to the computer. How to get the commands back and forth before the rig keyed seemed to be the problem. Solution, up the baud rate!
Ooops, 4800 did not work! And, at 2400 baud I still had the "race" problem. A quick note to W3IWI was shot off and Tom came to the rescue with the number of the IC to change.

It is a TLO84 and it replaces the HA17324 found in the MFJ TNC's. (Which is nothing but a LM324)

Since I have upped the baud rate I have had NO lock-up problems with the system. I would suggest that even if you do not have lock-up problems that you think about making this simple modification to any TAPR 2 TNC that you own.

Bill, WA2PVV

PORTED AND REALIGNED FROM PC TO AMIGA FORMAT BY BOB G0LBQ - N6XDI.