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The Johnson Viking Model 352 CB Radio.






E F Johnson 40 Channel CB Radio

One technique employed by a Silicon Valley firm when recruiting new employees for their advanced product division was to show a photo of an item and then ask the candidate... what do you see. The answers were all over the map but usually the successful candidates had a one-word answer and that was opportunity.  Today's post is about opportunity. 

If your response after seeing today's photo was a CB radio... you failed as you should have given the one-word response.

Many SSB CB radios have been "converted" to 10M operation and usually certain ones that have a programmable PLL are sought after. A bit of reprogramming and tweaking the RF circuitry and you are there. You can ask AI, and they will tell you the ones that meet that criteria, and you are usually steered to the PLL models.

Early on, before the PLL and when there were only 23 channels the CB radios used crystal synthesizers. Banks of crystals were selected so that through a mixing of crystal frequencies you generated the 23 Channels. You can see why the PLL's types are favored. To move the crystal synthesized radios to 10M required many new custom crystals. But no more.

One particularly interesting CB radio is the Johnson Viking Model 352 that used the 23 Channel Crystal Synthesizer and here is a block diagram.



The lower part of the diagram shows the Crystal Synthesizer and after all of that mumbo-jumbo produces a 34MHz LO and with a 7.8MHz IF (pretty much an industry standard) you get the CB frequencies.

Here is a frequency chart of the synthesized LO Frequencies.


You just know it's coming... Rip Out the Crystal Synthesizer. In its place and for $20 build an Arduino Nano based, Si5351 LO and small OLED display and program it for 35 MHz and you are on 10M after Peaking and Tweaking the RF Stages.

Actually, there may be a bit more involved to make it work on LSB, USB and AM but that could be addressed by having the Digital LO also generate the BFO signals. There are several Model 352's currently listed on eBay and a "beater" can be found for under $50.


But I keep forgetting, to do this you do have to know something with the 1st on the list is the ability to see opportunity followed by knowing something about electronics. The electronics part is like reading schematics and circuit tracing and how to program an Arduino. We are now back to less than 1% and maybe even only 0.5% who could pull this off. But the prize is a 10M SSB radio for less than $100 and you modified it. 

Them that know can make it go.

PS. Yesterday's poor stats on the number of blog viewers was simply a test that either there is a dislike of Gumbo or maybe Mike Johnson. Surely it was not about the 5763 Vacuum Tube. I keep data and it is telling. 

PPS. Think 6 Meters. With the Si5351 a CB to 6M conversion is on the table albeit a bit more complex.

73's
Pete N6QW


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