Dawn
Member
Looking through the archives, this has come up a few times and pretty much degenerates into nonsense of someone wanting to add ctcss to a cb and the absurd comments around that. I decided to move this from the Johnson thread to a general topic though.
Some of the early tube based cb's as was noted below with the response on the Johnson's had an external accessory for selective calling. While the option was available and the interface present, either there was never an accessory developed or there was little interest. Browning, Sonar, Johnson, Pace, and Lafayette in my experience were the only ones I've ever seen a factory manual mention availability of such a product. There apparently was a standard developed for the original, proposed, H.E.L.P plan that never reached fruition with the so-called 25 channel expansion that didn't happen. The Lafayette comsat 23 channel base that was identical to the earlier, short lived 25 channel HELP capable unit I worked on during the 70's still had the connector on the rear and it was noted in the schematic.
Other then Johnson's, I never seen a bonafide CB selective call system master call or mobile slave unit.
Several of the companies listed above made an AM business band single channel version of their CB's that was capable of power. Only system I worked on like this was a Kaar system in '73 that the company I worked for still supported. Pace and HyGain still sold units as late as '76 that I know of. The Kaar units looked much like a Sonar with no channel selector and were fitted with an aftermarket Speedcall IIRC LC filter based two single tone decoder that operated either group or individual call that was fitted after CB user incursion began to occur sometime after the 60's and wasn't a factory product.
This is a fascinating, but seemingly forgotten part of CB's past that I've always wanted to know more about. It would probably be expensive back then. Most encode/decode sytems even at audible frequencies were based on resonant reeds or torridal filters that required very precise tolerance parts. Phase lock loop chips like the '565 and '567 appeared during the early 70's along with phase shift oscillators or op amp based gyrator filters that could be forced into oscillation for encode at the same frequency. That still would have cost quite a bit and even then, were extremely unreliable due to drift if they used tunable components like 10 turn pots.
CB and AM would require an audible tone signalling system. The problem get much more complex with SSB and I have decades of experience with those system in marine and terrestrial hf networks used in latin america that the selcal units would have cost more then a high end SSB CB mobile or base. I doubt anyone ever used those types of systems on CB.
Any of you have any first hand experience with CB selective call with spec. details in particular or manuals? Nothing that I want to do, just want to understand what the companies were offering. While many old
CB books mention this in passing, none are ever specific about any of the systems used.
Some of the early tube based cb's as was noted below with the response on the Johnson's had an external accessory for selective calling. While the option was available and the interface present, either there was never an accessory developed or there was little interest. Browning, Sonar, Johnson, Pace, and Lafayette in my experience were the only ones I've ever seen a factory manual mention availability of such a product. There apparently was a standard developed for the original, proposed, H.E.L.P plan that never reached fruition with the so-called 25 channel expansion that didn't happen. The Lafayette comsat 23 channel base that was identical to the earlier, short lived 25 channel HELP capable unit I worked on during the 70's still had the connector on the rear and it was noted in the schematic.
Other then Johnson's, I never seen a bonafide CB selective call system master call or mobile slave unit.
Several of the companies listed above made an AM business band single channel version of their CB's that was capable of power. Only system I worked on like this was a Kaar system in '73 that the company I worked for still supported. Pace and HyGain still sold units as late as '76 that I know of. The Kaar units looked much like a Sonar with no channel selector and were fitted with an aftermarket Speedcall IIRC LC filter based two single tone decoder that operated either group or individual call that was fitted after CB user incursion began to occur sometime after the 60's and wasn't a factory product.
This is a fascinating, but seemingly forgotten part of CB's past that I've always wanted to know more about. It would probably be expensive back then. Most encode/decode sytems even at audible frequencies were based on resonant reeds or torridal filters that required very precise tolerance parts. Phase lock loop chips like the '565 and '567 appeared during the early 70's along with phase shift oscillators or op amp based gyrator filters that could be forced into oscillation for encode at the same frequency. That still would have cost quite a bit and even then, were extremely unreliable due to drift if they used tunable components like 10 turn pots.
CB and AM would require an audible tone signalling system. The problem get much more complex with SSB and I have decades of experience with those system in marine and terrestrial hf networks used in latin america that the selcal units would have cost more then a high end SSB CB mobile or base. I doubt anyone ever used those types of systems on CB.
Any of you have any first hand experience with CB selective call with spec. details in particular or manuals? Nothing that I want to do, just want to understand what the companies were offering. While many old
CB books mention this in passing, none are ever specific about any of the systems used.
