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Wednesday, November 4, 2015

CB to 10 Conversion? The Radio Gods Seem Ambivilent


A lot of trouble can begin with a 5 dollar purchase, as I found out after I bought a nickel bag of CB at a hamfest. 

The embarrassing little Good Buddy appliance has been hidden away in my junkbox for a while.  I pulled it out after watching Pete's videos about the conversion of his Ten-Tec Model 150A commercial rig.  I thought perhaps I could use a little DDS or PLL board to bring that CB rig onto 10 or maybe even 12 meters.  

The first thing I noticed when I opened it up was the smell -- there was a very strong chemical electronic smell.  It was as if components and wires and adhesives and PC boards had been venting inside that case for several decades.  This wasn't that pleasant electronics smell that you get from a Drake 2B or a DX-100.  No, this was different.  It gave me a bit of headache.  That's a bad sign.   I began to wonder if the Radio Gods might be sending me a message. 

But then I found this very cool conversion site:
http://www.jcoffman.net/WB5RUA/10_meter_AM_conversion_w_Photos.html

Wow, a few snips, a few jumper wires on the PLL board, and a few coil tweaks and that thing would be on 10 meter AM.  I also learned that the "Cybernet" board that was stinking up my shack was VERY common in CB rigs, so there is a lot of info about it on the internet.  This thing seemed to be crying out for a quick and easy conversion to ham-dom.  

So I don't know which way to go with this one.  I'm getting contradictory signals from the Radio Gods.  What do you guys think?  Garbage can or workbench? 




6 comments:

  1. If you warm it up for a while with the covers off, most of the smell should go away. Do this outdoors (summer sun, hihi) or in a vented area. An old toaster oven set to 100 F is good but costly. Sadly there are no more cleaning agents that I know of that could strip out that residue smell.

    Also check the number of CB to 10/6 articles in 73. Index here - http://www.w1sdm.net/cgi-bin/73search.pl Just put CB in the title box. There are links to Archive.org if you haven't downloaded the torrent or a big box of back issues. I love having both.

    Thanks for the podcast.

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  2. Try it! Nothing ventured, nothing gained! If the experimet is a failure, you still have a good QRP final amp, and an AM modulator.

    GL! Jason W6IEE

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  3. If you leave it on 11m it will be forever damned to be just a CB radio. However, converted to the ham bands it will live a exalted new life. If it had a soul, it would thank you.

    72/3
    Tony G4WIF

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  4. At least one of those 73 articles showed how to put them on 6meters. Mostly a matter of changing the front end and final tuned circuits, but also if I remember properly, they mixed the VCO down to another frequency using the 10.240MHz crystal oscillator, and that had to be shifted (by adding another oscillator of suitable frequency). But it was relatively simple, since with a 10.7MHz IF, the image was almost in the right place.

    I kept hoping to find an SSB CB set, and while I found some CB sets int he garbage and at garage sales, no SSB until a couple of years ago, at some sort of 2nd hand place. Only five dollars.

    That had more possibility for conversion, and I figured if not, the SSB filter would be useful in some project.

    But when I checked, this one uses a relatively wide filter, albeit in the HF range (I can't remember the frequency). For transmit, a wider filter doesn't matter, just restrict the audio bandwidth. For receive, I guess they counted on the channelized operation, since the filter wasn't anything but a good AM filter, and indeed was used for AM reception. So it wasn't a great SSB filter for cheap, though I would think earlier SSB sets had better filters.

    There's even a mod to this set, not sure what the switch hanging off the back does. Maybe I should use it with a transverter, get it on 6meters, where low power SSB, even with a "wide" receiver would likely do well when conditions were good. Or modify it so it's a 6m ssb transceiver, find a small battery to run it, and then go portable in the summer.

    Someone had a pair of conversions in 73 for putting the CB sets on CW. That may have more use than a low power AM transceiver. And you can always improve selectivity by finding a better filter, or adding a q-multiplier, or finding a ceramic resonator for the 2nd IF frequency, usually 455KHz in CB sets) to make a single crystal filter like in many of the old good receivers.

    Michael

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  5. People have modified cybernet to various hambands between 40m and 6m. I'm unsure if the 4m (70MHz band in europe) conversions ware successful.
    I have few scrap cybernet cb's waiting for inspiration in the shack.

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  6. I recently did a conversion of a cybernet based CB by purchasing a crystal (actually 10 crystals) off ebay for $3 that is in the 12 mhz range and cut and changed a few wires going into the PLL, putting channels 31 to 40 on 29.000 to 29.090. Last month when the band was in better shape, I worked a number of folks in Europe as well as west coast US with it and a little 25 watt amp.

    A few years ago, I did a conversion using a VFO/DDS in place of the mixer crystal, which worked pretty well but then I found out that for AM or FM, just about everyone on 10 meters is using channels 10Khz spacing starting at 29.000, so the ability to vary frequency between the channels is actually undesirable.

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