[aprssig] Waveform (signal) on MX614 RXIN pin?

[James Washer]

I'm working on a TNC based on an MX614. I'm not seeing anything useful on the RXD pins, so I took a look at the RXIN pin. The waveform there is most interesting. There's about 2Vdc bias. Further, signals get clipped at the 2V, I see the bottom halves of the sine waves below this 2V clipping, but never anything above it.

I'm wondering if any of you have both a scope AND a working MX614 tnc and could tell me what you see on pin 5.

This may be normal behaviour, caused by the tie between pins 5 and 6(RXAMP), but since I've never seen anything like this before, I'm just not sure.


THANKS and happy new year.