Transmission At Last - G7SYW's amateur radio bits & bobs...
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Transmission At Last

| Posted in Misc stuff

My first venture into the world of transmission, SWR and antenna resonance came in 1980. It was then I purchased an AM CB radio, all very illegal in the UK at the time.

In late 1981 the UK was given a legal CB system. This used FM and slightly different frequencies to the AM CB’s to prevent conversion of existing AM radios and reduce possibility of RF interference.

The use of CB in the UK became a bit of a “craze”. With this came users with low technical skills resulting in lots of radios having blown finals. Blown reverse polarity protection diodes, these gained the nickname of wally diode, were a common fault also.

With the outlawing of the “old” AM and SSB radios CB shops wouldn’t repair them. With my interest in electronics this lead me nicely into being the local “rig doctor”.
Repairing these “blown” radios for the local users encouraged me to learn more about the various circuits, how they worked and how they were interconnected and interacted with each other.

Quite a lot of my work was with SSB radios as these were quite popular at the time, mostly the Cobra 148 GTL-DX. The biggest request was to modify them to give them extra channels to cover more of the 11M band.
Cobra 148 with BRL200 linear amp

Of course I used to use one myself along with Bremi BRL200 linear amp and an Avanti Sigma IV antenna.

For those interested, I have the service manuals for the Cobra 148 & the Sigma IV which can be found on the downloads page here