TNC Audio Break-Out-Box

Here is a handy little break out box for insertion between a TNC and the radio for the purpose of monitoring or injecting test signals.

The device has a pair of banana/screw terminals for the transmit and receive audio paths, and a PTT switch assembled in a small die cast box with rubber feet, and a plug and socket for the common (standard?)  TNC2 audio connection.

This is an ideal way to calibrate the modulation sensitivity of the transmitter or receiver. A milli-voltmeter, oscilloscope or PC sound card with Spectrum Analysis application can be used to ensure optimal set-up, or diagnose problems with either the transmitted signal or off-air signals.

See my pages on FM and AFSK Overload for applications.