CONVERSION OF THE BC611 RADIO TO MODERN CB CAPABILITY

.

by

Charles C. Roberts, Jr.

Have you ever wished you could convert your BC611 radio to CB capability without cutting holes or tearing the unit apart? Many collectors have developed a respect for antique military equipment and are committed to its preservation. The following is a procedure on how to convert your 611 to CB while maintaining its integrity and authenticity. Lets get started.

radioFigure 1 Remove original chassis and antenna

radio2Figure 2 Remove original speaker, microphone and battery plunger

Figure 1 shows the BC611 with the antenna and chassis removed. Sufficient room must be made available for the new electronics and battery. Figure 2 shows the removal of the original speaker ear piece and microphone. It may be possible to interface these items to the new electronics but you will have to come up with connectors and a compatible impedance circuitry. Also don't forget to remove the old battery plunger at the top of the unit to make room for new batteries. The next step is to get a CB radio (Figure 3) to fit in the unit.

cb radioFigure 3 Get a CB radio

The one used in this example is the Realistic TRC-218, 2 watt, 3 channel capability, citizens band transceiver normally found at electronics stores. Figure 3 shows the basic radio which is similar in design to several other brand radios. The next step requires open heart surgery on your CB. Open the CB radio and record where the wires go, locate microphone, and speaker as shown in Figure 4. You have now violated the manufacturer's

inside cbFigure 4 Open CB, record where wires go, locate microphone, and speaker

warranty so there is no turning back. If you accidentally zap an electronic component you are out of luck with regard to warranty work. If you are still interested in proceeding, Figure 5 shows the next step. Remove electronic chassis and cut as few wires as possible.

radio coverFigure 5 Remove electronic chassis and cut as few wires as possible

The basic premise here is to get the chassis, control dials (on/off, volume, squelch), ear piece and microphone out of the unit to be installed in the BC611.

wood baseFigure 6 Make a wood chassis mounting board

Figure 6 is a sample chassis mounting board made out of 1/4 inch plywood to hold the electronic chassis. (dimensions are left edge 2 inches, bottom edge 11 inches, right edge 3 inches, top short edge 3 inches) This acts as an insulator for the circuit board and a mount to keep the board from shifting while in use. It also acts as a mount for the aerial and control dials.

electronicsFigure 7 Mount electronics on wood chassis mount

Figure 7 shows the electronic circuit board and antenna mounted on the wood chassis mount with wood screws. Place the wood screws through the holes used when mounting to the plastic case. Mount the aerial in a convenient place near the antenna lug but properly aligned with the top cap of the BC611. Tape the aerial to the circuit board. Pry off speaker and microphone and solder in extension wires (Figure 8). Try to use similar gauge extension wires. Computer tape cable works well. Soldering the connections and insulating with electrical tape

chassisFigure 8 Pry off speaker and mike, solder to extension wires.

is usually adequate. Cut the battery case to fit in one slot of the BC611 and solder in extension wires. Make sure the channel selector switch is set to the appropriate channel. Figure 8 shows the final product ready to be tested and inserted into the BC611. Figure 9 shows the taped electronic circuit board used to reduce the chance of short circuits.

tape chassisFigure 9 Tape electronics to reduce chance of short circuits

switchFigure 10 Install key switch actuation wire inside a piece of Teflon tubing

Figure 10 shows the installation of the key switch actuation wire inside a piece of Teflon tubing. One must come up with a way to actuate the transmit (key) switch when the unit is installed in the BC611. A simple way is to attach a thin wire to the switch and run the wire inside a Teflon tube. The Teflon tube insulates the wire and also directs it in a manner similar to a throttle cable on a lawn mower. Remove the key switch assembly from the BC611 to reduce interference when the chassis mounting board is inserted. Un-solder microphone and speaker wires and mount the microphone and speaker in the ear and mouthpiece re-soldering and insulating the connections. Placement of flexible foam over the microphone will help reduce feedback and ringing on the microphone circuit. Insert electronic chassis on side of BC611 nearest the key switch (press to talk switch) as shown in Figure 11.

insertFigure 11 Insert electronics

install keyFigure 12 Reinstall key switch

Reinstall key switch with actuation wire protruding through opening nearest the ear piece as shown in Figure 12. Install a metal spring clip to aid the key switch in returning to its original position and adjust the key switch actuation wire for proper operation (Figure 13).

switchFigure 13 Install a metal spring clip to aid key switch return

radioFigure 14 BC611 is now converted to CB

Presto, your BC611 is ready for the next battle (Figure 14). Remember you will have to open the bottom cover to turn on the CB and adjust squelch, the price one pays for not cutting holes in the radio. The batteries (8 AA, or 10 AA rechargeable) should last for several hours after initial turn on and adjustment may only be required once during a battle.

Copyright 1995 Charles C. Roberts, Jr



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