In article ,
Radioactive Man wrote:

Well, I should point out that I'm not using a regular TNC. I'm using
this: http://www.ringolake.com/pic_proj/zcd/zcdmodem.html

It has worked very well with my little mighty Yaesu VX-2R, just not
with the Icom IC-2N.

Did try the volume this evening...I was only able to decode packets
with the volume at least 3/4ths. And even then it wasn't packets from
the local repeater, but from my Yaesu in the other room.

This mdemless TNC design looks to me as if it might be rather
vulnerable to the presence of high-frequency noise in the audio
signal. It's not using conventional bandpass detection, but is using
a simplified zero-crossing detector. High-frequency audio noise could
cause spurious zero crossings, which the firmware in the onboard PIC
might not be filtering out adequately. The IC-2N may have a "hotter"
receiver section which could be passing through more noise from weaker
packet stations.

First thing I might try would be adding a low-pass RC filter - one or
two stages - with a cutoff frequency of 2500 or 3000 Hz. Adding a
series capacitor to act as a high-pass filter at 800 - 1000 Hz might
also help.

--
Dave Platt AE6EO
Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior
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