[aprssig] paccom schematic

[Bob Bruninga]

> Yes the tones are clean and not distorted. 
> The high tone is about 6 db lower 
> in amplitude the low frequency tone.

Some TNC's really hate  a tone skew like that.  I cant remember which one is ihger, but one skew is worse than the other.  

Try improving it with a high pass filter in front.  With a low end roll off starting at 300 Hz.  That should balance the tones.   If input impedance of the TNC is known, say 600 ohms, then about a 0.47Uf in series on the input might do it?
If you have plenty of audio level, just use a 0.1uF or smaller for a wuick test.

Bob, WB4APR