Somehow [hvde] wound up with a CB radio that does AM and SSB on the 11 meter band. The problem was that the radio isn’t legal where he lives. So he decided to change the radio over to work on the 6 meter band, instead.
We were a little surprised to hear this at first. Most radio circuits are tuned to pretty close tolerances and going from 27 MHz to 50 MHz seemed like quite a leap. The answer? An Arduino and a few other choice pieces of circuitry.
In particular, [hvde] removed much of the RF portion of the radio, leaving just the parts that dealt with the intermediate frequency at 7.8 MHz. Even the transmitter generates this frequency because it is easier to create an SSB signal at a fixed frequency. The Arduino drives a frequency synthesizer and an OLED display. A mixer combines the IF signal with the frequency the Arduino commands.
The radio had a “clarifier” which acts as a fine tuning control. With the new setup, the Arduino has to read this, also, and make small adjustments to the frequency. The RF circuits in the radio took some modifications, too. It is all documented, although we will admit this probably isn’t a project for the faint of heart.
As much as we admired this project, we think we will just stick with SDR. If you want to learn more about the digital synthesis of signals, check out [Bil Herd’s] post.
The advantage of this over sdr is you get TX with a bit of power and no need to have a computer.
These larger cbs are great to work on as well – large components and plenty of space.
The mods required to do such a conversion look a lot more complicated than they really are.
Looking at a circuit of a CB the first time can be a bit overwhelming but as you start to break it down into the various “modules “ it does become easier to understand.
Thanks, Very impressive!. Can you send me instructions on the build and to operate on other frequencies? Also wondering about, have seen AM only CB converted to have SSB, How is this done?
Thanks
George
Starting in tye late seventies, when the US switched from 23 channels to fkrty, there were a lot if surplus CB sets on the market, many unused, as wekl as working boards needing cabinets. That even included 40 channel units.
Witu CB being almost adjacent to 10metres, there had always been some conversions to ham use. Early sets using 2 crystals per channel were simple, change crystals and a tiny bit of retuning.
But the late seventies brought “endless” articles aboit conversion, mostly synthesized rigs which required more work but gave 23 or 40 channels in 10metres. Some were hard to convert, the circuitry cesigned to make it harder to change frequency.
Other than modifying the frequency range, people wrote about converting to CW, making them FM (on 10m FM is interesting, snapping in and out with good band conditions) and moving to six metres.
Moving to six meant rewinding a few coils, nkt really a !ot of work. In the early seventies there was one commercial 6m SSB rig that looked like a CB set, complete with 23 channels.
I long hoped to find an SSB CB set, but onky found one about five years ago, and one with the harder to modify synthesizers, so there it sat. Only five dollars at least.
But recently I have thought about using one of those arduino synthesizers to just replace the existing synthesizer, a now cheap and easy process, I think. And move it to 10m.
Though with homebrew ladder filters, building an ssb transceiver is now fairly simple and cheap if single band, maming the CB set less important. The arduino sybthesizer takes care of the complicated work. Time will tell.
73 Magazine carried most of the CB conversion articles forty years ago, there probably is a specific list of them somewhere. And the issues can be gotten at archive.org and other places.
Michael
yes the 02A and 858 PLL chips made mods easy – there was evn the UFO digiscanners which in one incarnation replaced the internal PLL with an external one to expand the coverage – though limited by the tuning range of the standard filters. it was a wild time in CB land in the 70’s and 80’s
The PLL02A ran at around 3.5Mhz which lent itself to a simple frequency agile 80m CW transmitter.
So the headline should read: CB Radio + Arduino + A Few Other Choice Pieces of Circuitry = 6 Meter Ham Band
nice, but does it have echo and a roger beep?
I’m a ham operator of twenty years + these conversion are not to be confused with ham radio, to cb radio’s.
If it’s a conversion of a CB radio to use on any ham band, then it becomes a ham radio. Plenty of people have converted CB radios for use on 10 meters, and then used that converted CB as a driver for a transverter for 6m, 2m and 440mhz (for satellites), 1296 mhz, and microwave work. What possible confusion could there be, JOHN?
I converted myself from CB radio to a ham. So many hams knock CB when they should be embracing those with an interest in radio. I passed the test with flying colors on the first go because I read an old second hand ARRL handbook front to back like it was my job when I was a kid. It’s attitudes like John’s that keep me off the air.
Yeah JOHN?!
This is actually pretty old school. Back in the days when hams had to walk six miles through the snow to change frequencies, it was pretty common to use a transverter. Lots of old rigs have IF output on the back for this. Not sure that there’s much 6m activity on AM or SSB but it’s worth a try.
He does not go into detail about re-turning the front end or PA section. I wonder what the receive sensitivity is? What components did he swap out? (Change caps with 50% values, etc)
That’s a interesting reading. Where does he live that a CB-Radio on 11 meter band is illegal, but ham radio on 6 meter band is legal?
In Germany it would be the other way around. For Hamradio on 6 meter band you need to have a license. CB Radio is free to use even on the 11 meter band.
Anyway, kudos to him and very interesting to read!
Greetings,
Daniel from Germany