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AD-913 Simplex Radio Adapter





Most modern mobile radio systems are FM and are equipped with a squelch or mute facility so that the radio is silent in the absence of an incoming signal. The AD 913 is intended for use with such a system and use with AM, SSB or other systems without mute is not recommended.

As there is such a wide range of compatible transceivers it is not possible to give definite instructions for setting up but the diagrams at the end, however, should be able to offer a guide to most systems.

The "loop through" wiring to the rest of the outstations is via the 3-pin XLR type connectors wired as follows:-

Pin 1 - Ground

Pin 2 - 24 volts

Pin 3 - Audio Line


The "loop through" output cannot be used except with very low power transmitters (less than 100 mW output). Therefore the AD 913 normally has to be used as the end of a line or as a spur to a line. (A spur can easily be set up with an SB 901 Splitter Box).

This spur or line must be a minimum of 3m long and kept straight, without loops etc, and must point away from the remainder of the wired circuit. The transmitting antenna is then placed beyond that. In other words, with the exception of the AD 913's own cable the antenna must be at least 3m from any other part of the wired system.

Example: The existing wired circuit runs along a wall. A spur is taken off this and taken at right angles away from the wall for at least 3m and plugged into the AD 913. A walkie talkie is connected and placed further from the wall still.

For use with higher power transmitters, typically mobile units or fixed base units the above still applies. However these units do not have an integral antenna and this should be located still further from the wired circuit, up to 10m away, unless there is a metal screen in between, e.g. a vehicle roof.

Pin Outs :-

  1. Screen
  2. Tx audio
  3. Screen
  4. Rx audio
  5. GND
  6. PTT




With the system connected and switched on, the operating levels should be adjusted. Without the signal flash lamps activated, set the volume control on the radio set to mid track, and adjust the squelch for correct mute operation, if fitted. Transmit normal speech from a remote unconnected transceiver;. this should be heard on the main wired system. Adjust the "receive" preset on the AD 913 until this remote radio signal is heard at a reasonable level.


Next press the signal flash lamp on the wired outstation and speak into the system. The remote unconnected transceivers should be able to hear the speech. Adjust the "send" preset on the AD 913 until the speech is heard at a reasonable level in the remote transceivers.


Last Modified : 09 February, 2006