Dan's Radio

CB Radio

How We Got Into Broadcast Quality AM

  Back around 1998 while listening to some alternative free speech broadcasters on the shortwave bands, I heard about how people were using low powered AM and FM broadcasting to reach the people with alternative information, and most of their concerns then were for some conservative kinds of information being provided to people of which was being censored by the main stream media.

  In considering this, along with my experience in CB Radio repair since the mid 1980's, knowing that CB Radio can transmit further than low power AM and FM transmitters of the FCC Part 15 kind.  I decided to see what can be done to enable people to use their CB for emergency broadcasting and clandestine radio purposes.  I envisioned that someone could rebroadcast alternative media from the shortwave radio bands across the nation, given the right conditions for DX propagation, as well as locally with regularity.

  Well I spent some hours in them days looking over the circuit diagrams, devising minimalist kinds of circuit modifications to provide my CB's with Broadcast Quality AM and tested them with various resources via line level inputs.  I went on to test those radios with a Sterba Curtain antenna to see what a legal limit bare foot radio could do with a good antenna, although the antenna is not commonly  used for CB Radio.  I think I might have been the first to have used this antenna on 11 meters, and I have built and used two of them down over the years since about the late 1980's.

  In testing the radios on the airwaves, along with the curtain antenna, I realized that one could effectively reach the nation with information, especially during the peak of the sun spot cycle.  Since then I have come across some recent interest in Broadcast Quality AM, misinterpreted as being HiFI CB modulation which is incorrect, although the idea is in the right direction.  And so, I realized that this is not a trend rising up through the CB ranks and is the way of the times.  And so I decided to get with the times and resurrect my work from them past days.

  Now these modifications help the CB radio operator in a most needed way by helping to keep their signal clean on the airwaves, via confining their audio within the specified channel bandwidth and hence preventing adjacent channel interference in terms of bleed over.  Narrowing the bandwidth down for Broadcast AM along with a focus on the ALC circuit performing as it is meant to and adjusting it properly with an oscilloscope amounts to a nice clean signal.

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