The Development of The First CB repeater (or Owed to an Elastic Band!) – A simple but effective repeater by an anonymous contributor!
Back in the mid eighties, known by CB’ers as “the good old days”. There was a lot of CB’ers in my local town. There was also a guy who lived on a farm on a hill high above the town. His outlook was brilliant and his CB contacts made us all wonder if he was talking to himself and just winding us up. Until you visited his house and realised what an advantage several hundred feet extra height gave you.
This extra coverage caused Bob (not his real name but since he is now a respected radio amateur I’ll keep his identity secret) a problem. Everyone was always asking him to relay messages to other CB’ers out of their range. So one night he says “I’m going to build you guys a repeater so I can get some peace”. Then came a thoughtful pause as a dozen separate CB’ers thought the same thought.
All us CB’ers at the time had two CBs. We all had UKFM rigs and multimode multi-channel rigs as well. My station at the time was a Tristar 747 and a Rotel 220. So one night we are talking on 39 UKFM and Bob says, “listen down on channel 3, 26.985mhz FM”. He had a Ham International multimode 2 and a UKFM 40 channel set both with silver rod antennas, one at either gable end of his house. He tied an elastic band round the multimodes microphone and laid it beside the speaker of the UK rig. Thus a crude repeater was created. We talked on UK 39 and heard the reply, through Bobs rigs, being retransmited on CEPT channel 3 (CEPT was not to be legalised for another few years, but for the sake of accuracy, I’ll describe it as such). Channels 3/39 were chosen because they were empty at the time, but when we thought about it was *almost* a 1Mhz split, so they were adopted as the official repeater input and output.
Being resourceful little pirates we made rigs with a repeater shift. This entailed hard wiring our two rigs together. Since most multimodes will receive with the Mic unplugged we had to switch the input and output channels round, so CEPT channel 3 was now the input to the repeater and UK 39 became the output. At that time my station was my Tristar with a 5/8th rod and my Rotel with a DV27 in the attic. I had one mic with two plugs. Its transmit switch and transmitted audio plugged into the Tristar, but since the receive link in the mic was not needed for the tristar it was taken out on a lead and plugged into the Rotel mic socket. So when I transmitted on the Tristar, the receive was disabled on the Rotel, thus I didn’t hear myself on the output channel and experience feedback. The volume control on the Tristar was turned down, but could be turned up as a “listen on input” feature. Later my station developed to a Ham International multimode 2 and a Rotel 240, but the wiring remained the same.
Some guys built a similar twin rig set up for mobile use (I was too young to drive at the time) and I saw one mobile station which had the receive link from the mic switching a relay. Which not only disabled the receive on the UK rig but operated a coaxial switching relay, thus the two rigs could work off the same antenna.
But the repeater still required manual operation of the elastic band. So thought was put into this. The receiving rig was replaced with one which had additional crystal filters added to combat adjacent channel bleed over. Thus the input wasn’t desensed by the output. Cavity filters would have been nice, but beyond the repeater groups funds, which consisted of the elastic band which was donated by an anonymous benefactor after the original failed. The external speaker socket of the multimode was wired through a resistor network which was never revealed to me in detail, and then into the mic input of the UK rig, which was switched to permanent transmit. The elastic band was now redundant. I assume it was returned to its original owner. Bob could still contribute to our repeated debates by transmitting on CEPT channel 3 on another rig into a dummy load. He was close enough to be received by the main repeater antennas and be relayed out on UK channel 39 and he could listen to the reply on a speaker connected to the resistor network.
The repeater was still manually operated in so far as it had to be switched on and off by Bob, which meant we couldn’t use it unless he was at home. Since Bob’s electronics skill ran out at guitar amplifiers we enlisted the help of the local rig doctor who was a magician of very high repute. He fitted a relay to the squelch control of the channel 3 receiving rig so that it would switch the UK rig onto transmit when the squelch opened. Hey presto, fully automatic. It stayed switched off during the day when the skip was running, as it would be switching off and on all day, but about 8pm it got switched on and we all used it. The committee / assorted bumpkins were working on a tone-burst system to access it when Bobs parents sold the farm and moved into town. The repeater shut down never to appear again.
The repeater was very well accepted by the local CBers, who marvelled at such technological breakthroughs. It was even heard being discussed on the local 145Mhz repeater by two hams who were not unimpressed by the resourcefulness of us cheapskate CB’ers. After that the repeater earned the nickname GB3CB. I wonder where it is now?
Anonymous but can be contacted via TM1