PRR-9 PRT-4 Battery Information

                   Page updated March 2018 to include suggestions for using a diode for reverse voltage protection on home brew battery packs.


             We lost a lot of lives in Vietnam, and thousands came home wounded and disabled - -what a waste. And for what. . . And the best part was when you returned you got treated like krap.


  The PRR-9/PRT-4 combination is a great hamfest/military Rally set. Most of the sets had crystals installed for the 51.0 Mcs Push. Fabricate a simple "Snatch Plate"mount on a flat sheet of aluminum, mount your transmitter and receiver and you have a hand held. When the receiver is close to the transmitter feed back can occur, you have to reduce the receiver volume or use a ear piece.


                              Back view of the "Snatch Plate".   

                        My transpiration at the Gilbert Rally with the Snatch Plate unit installed.

                   The BA-505/U battery is fairly rare and if you find one it will probably be depleted.
       Connector end of the 505 battery. Note the large and small female socket pins.

                 You can attempt a rebuild with N Nichel-Metal Hydride cells but I put that project in the "Too Hard to Do Box". Perhaps just salvage the connector and use a 9 volt battery or fabricate your own connector as shown below. Just in case you decide on the N cells be sure and order the cells with "tabs".

          A receiver battery connector can be fabricated using 5/32 and 1/8 brass tubing available from any hobby store. The shell is from a Jones connector. Cut the tubing to length, insert into the shell and fill with epoxy.

            The receiver connector. Not the larger PLUS pin is marked. NOTE: I do not see any reverse protection on the receiver schematic so hook up power carefully especially when using those clip leads from the ham fest. Or install a protection diode in series.


         The center shell is filled with epoxy to hold the brass tubing. The larger plus side is marked.

     NOTE: I do not see any Reverse Voltage Protection in the receiver- - be sure and apply voltage properly.


                          The fabricated receiver battery connector in place.

                      The receiver requires 6 volts, I used a 100 ohm resistor to drop the voltage. It has been reported that if you use 9 volts to power the receiver that the receiver will survive but that the squelch will be inoperative due to the high voltages and the bias changes. Another suggestion is to a reverse protection diode which should provide about a .7 volt drop.


      I cleverly concealed the 9 volt battery with "One Hundred Mile An Hour Tape".
      Next in our battery saga is the PRT-4 battery, the BA-399/U, 15 volts. It is fairly easy to rebuild the pack and to insert two (2) 9 volt batteries. I have not heard of any problems with the PRT-4 being powered at 18 volts, running it at a slightly higher voltage.  

            The PRT-4 Transmitter battery the BA-399/U can be found at hamfests etc. Start by carefully removing the cardboard cover.

              The main connector is mounted to styrofoam on the left.

                Take the connector and it styrofoam mount and use that for one end of your new battery box.


                  Some battery connectors may have to be modified in order to accommodate two 9 volt batteries inside the new box.

                      Be sure and install a trap door on your box for future battery replacement.

          A glue gun comes in handy.

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