The following is a suggested circuit for connecting a packet TNC
to a Kenwood TH-series HT. Included is the TH-21/31/41, the TH-
205/215/315/415, and the new TH-25/45 series HTs.
The connections are as follows:
A sub-miniature plug is used for receive audio. The tip of
this plug is audio out; the sleeve of this plug is the
common ground for PTT, transmit audio, and receive audio.
A miniature stereo plug is used for transmit audio and PTT.
Connect the middle "ring" of the plug to the TNC audio out
through a 0.2 uf cap (for DC isolation). Connect the sleeve
of the plug to the TNC PTT. The plug's tip is unused.
Set the TNC audio for 50 to 80 mv audio output into a 2K ohm
impedance.
