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TNC Audio Break-Out-BoxHere is a handy little break out box for insertion between a TNC and the radio for the purpose of monitoring or injecting test signals. Figure 1: TNC Audio Break-Out-Box
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. |
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