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Recording from a radio Accessory Connector

Most radios have an Accessory Connector at the back of the transceiver. In most cases, the following audio outputs (pins) will be available on the Accessory Connector: Tx Audio, Rx Audio and Audio Ground.

It is possible to record the ‘to’ (Rx) and ‘from’ (Tx) audio by connecting the Rx Audio and Tx Audio outputs to an analogue channel of a Total Recall VR.

  1. To record the Tx communication only, connect the Tx Audio and Analogue Ground pins directly to an analogue channel of a Total Recall VR.
  2. To record the Rx communication only, connect the Rx Audio and Analogue Ground pins directly to an analogue channel of a Total Recall VR.
  3. To record both the Tx and Rx communication use a Total Recall VR Radio Mixer to combine (mix) the Tx Audio, Rx Audio and then connect the combined output to a Total Recall VR analogue channel.

Common mistake is to connect the DC Ground pins on the Accessory Connector instead of the Audio Ground. In this case the recordings will contain a constant ‘hum’ or Total Recall VR will not start recording at all.

Other common mistake is to connect the speaker (usually pins Speaker + and Speaker -)  to an analogue channel of a Total Recall VR. This can work, but an impedance mismatch exists (4/8ohm vs 600ohm) which can damage the Total Recall VR analogue channel card as the currents that drive the speaker are much higher ( as they need to drive a 4/8 ohm load instead of 600ohm). It is possible to use a transformer to convert from 4/8ohm to 600ohm impedance, but this looks very ugly when deployed and we do not recommend it.