Radio Shack Simplex Repeater Controller (19-345) 
Conversion for use with Military radios with U-229 Connectors

© Brooke Clarke 2000 - 2007


Radio Shack 19345 Simplex Repeater Military Radio Conversion

General Information

This product may not longer be offered by Radio Shack.  For info on Simplex Repeaters see the Simplex Repeater web page and there's also a Yahoo Group for them.

This unit is made up of a 30 second digital voice recorder and some circuitry to turn on the recorder when audio is present and to play back the message when the audio stops.  By connecting to a single Receiver-Transmitter the combination becomes a Simplex Repeater.

The interface to the radio consists of only three wires:

It is not clear to me how this keys the transmit function in a Family Radio Service  (FRS) for which this unit was designed.  Although I have heard that it will work with the Radio Shack 2 meter radios.

In order to get it to work with the PRC-68B and PRC-126 I added a 4.7 K Ohm resistor (RS 271-1330) and a 2N2222A (RS276-2009) transistor plus a cable with a U-183 AUDIO connector.  A standard U-229 type cable could be used since the center pin is not functional in this setup.  The cable was from eBay and is sold as a KG-99 to PRC-104 Crypto-Audio cable.  The 26 pin connector (MS3126E16-26P) was wired with the pin letters matching the pin letters on the UG-183 (A to A...F to F).

It is wired as follows:

By wiring the AUDIO E wire to the external power supply pin on the 19-345 the external 12 VDC power adapter (RS-273-1662 w/ + to tip) will also power the PRC-126 or PRC-68B  radio but NOT the PRC-68.  The 19-345 may control the PRC-68 and supply power if the switch on the PRC-68 is set to OFF!  In this position the radio runs from the AUDIO pin E power supply.  The 300 mA transformer shown n this page does not have enough current to drive the 19-345 and the PRC-68 so a 500 mA wall wart is needed.

Note that the volume control of the RT being used as the repeater must be adjusted for best sound quality.  If it is set all the way down the 19-345 will not hear the audio.

Photo of component side of stock printed circuit board showing the voice chip and what may be an 8 pin PIC microcontroller.  Pin 3 on the microcontroller is the high = play pin.

Before Mod after mod
Before Mod
After Mod

Here is another way to make the conversion to mil radio use by Federico Torres, KP4KSL Annotated Photo.bmp -  
P.H.S.Ltd -2-Way Radio Range Extender -

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