[Packet] Packet and HTX-252

[Justin W. Pauler (W5JWP)]

Hello everyone.

I recently aquired an HTX-252 at a very, very cheap price. I would like to
use this radio with my Kantronics KPC-2 for APRS work. However, I have tried
and tried and tried to get the pinouts correct but nothing seems to work.
Can anyone shed some light on this issue?

The TNC seems to have the following pin layout:

	1 tx audio
	3 ptt
	5 rx audio
	6 ground

The Radio has the following layout:

	1 mic audio AND ptt
	4 5 vlt
	7 ground

While this looks very simple, it is rather complicated. If I touch Pin 3 on
the TNC to pin 1 on the Radio, it sits there, waiting for the TNC to key the
radio (which works!).

However, if I touch Pin 1 on the TNC to Pin 1 on the Radio, it keys the
radio no matter what. It stays an open key.

Now, if I put all three wires together at once, it open keys the radio and
stays open, but I can type something in the TNC and it will transmit it. I
can hear the tones going out.

Does this mean I need some type of resistor on the TX audio line to not open
unless there is audio present, and if so, what value would you suggest?

Any help would be appreciated and any other comments you have about using
this radio in a packet enviromnent. Thanks in advance.

--
Justin W. Pauler, W5JWP
ARRL OES, Louisiana Section
E-Mail: justin@w5jwp.org
WWW: http://www.w5jwp.org