Nervous 10M question

[VE3LYX]

I am a bit nervous asking this but I dont know so I have no other way of finding out. A friend gave me two old AM CBs. Modern enuf to be transistorized and I believe PLL as they have only three crystals in them. I have heard but was never involved that they can be moved to 10M Am with ease, in some casses simly by changing the reference crystal (which ever one that is?) The two units he gave me are a Cobra 29xlr and a Citizen  MPL-2 (40)
I used to have a Radio Shack 10M ham rig but gave it to a missionary Ham in Africa who needed it much more than I. It was lost during an uprising in Ivory Coast. I wouldnt mind having a QRP 10M AM in the shack . If I am committing some unwritten unpardonable sin please forgive me. However I know in a group like this there has to be someone who knows how to do this. I had read 11mc crystal to 12 mc crystal or something. Which Crystal?
Don VE3LYX

[Pete, WA2CWA]

The schematic and/or the block diagram should provide enough information on which crystal(s) might have to be changed to move both the receiver and transmitter oscillators or mixers up to 10 meters.

[K3ZS]

I have done this in the past.   The three crystal CB's can easily be moved up if there is an 11.8066 Mhz crystal.    This crystal is changed to a higher frequency frequency crystal, the difference in frequency is how much higher you want the CD to go.   In other words, if you put in a 12.8066 Mhz crystal, the 27 Mhz frequencies would be changed to the same except  1 Mhz higher.     You will have to retune the drivers, and final amplifier, the phase lock loop oscillator coil and the receiver RF stages.  I may have a useful crystal somewhere, I moved one up to AM part of the band but eventually converted the same CB board into an FM transceiver for that part of 10M.

[W4EWH]

I am a bit nervous asking this but I dont know so I have no other way of finding out. A friend gave me two old AM CBs. Modern enuf to be transistorized and I believe PLL as they have only three crystals in them. I have heard but was never involved that they can be moved to 10M Am with ease, in some casses simly by changing the reference crystal (which ever one that is?) The two units he gave me are a Cobra 29xlr and a Citizen  MPL-2 (40)

Don,

No need to be nervous: converting commercial units to ham radio is one of the best parts of our hobby. Most two-meter repeaters were made from converted commercial units before the market was big enough to interest manufacturers in putting out a "ham" version, and my first two-meter transceiver was a converted Marine-band FM unit.

It gets better: some years, ago, the ARRL published an article about doing exactly what you want done. The author, whose name I can't recall, said that "Demand exceeded supply" when he asked for HQ volunteers to try out the converted CB sets on 10 meters in Newington.

Unfortunately, I don't remember the date it was published. I've asked the ARRL Librarian to search through their morgue and call me back, and I'll pass along any information I receive.

For now, please check out these URL's:

http://www.qsl.net/wj5o/cb2bcn.htm
http://forums.qrz.com/archive/index.php/t-60042.html
http://www.jcoffman.net/WB5RUA/10_meter_AM_conversion_w_Photos.html

Long story short: relax, it can, and has, been done, and in many ways by many different people. Cab drivers in the Boston area routinely use "Outband" CB sets that have been "swung" to a bootleg set of channels so that they can keep up-to-date on traffic, and I'm sure there is expertise available.

HTH.

73,

Bill, W1AC

[W6TOM]

 Go for it!! I did the same thing to a Side Band CB 20 years ago, also used a varactor diode to allow me to move a bit off the channel. I had a 1/4 wave vertical on the bumper of my 67 mustang, one day at lunch time  I worked a few stations in MA from the Bay Area.

[VE3LYX]

So I checked out the websites. It was recommended strongly one check the radios FiRST to see if they actually work. Both are pooched and hve been worked on as well. One even had the pin 8 freq mod and two extra wires added. I dont know were Mike got them and I doubt he remembers now. Thought maybe an old cast front Johnson Messenger would be nice to play with. I could make a vfo and have a decent radio. Found some but ships "US only" . $%^&*(
???for now I will just look around to see what is available. .
Don

[VE3LYX]

Keeping in the 10M vein I have been working on a AM transmitter receiver deal built in a small file box. Each section uses a 12ax7. I have it running and am doing further testing this morning. It runs on a 12 volt vibrator supply. If it works well I may add another 12ax7 as a HF PA as they actually pack a reasonable punch in parallel form. I am fighting the urge to add two 12ax7 for what would be essentially a Quad 4 with 2 tubes.
Don VE3LYX

[KB2WIG]

D,

If yer interested, i'll be home fer most of the day. My 10m clothes line ant is pointed north-n-south. Shoot me a PM if you are interesting.


klc

[VE3LYX]

I am interested but not quite ready. No 10m clothesline (about 3/4 done)and still working on the modulation vrs the proper impedance mic. I went through this with my Mixer tube rig (which will be on 10M soon too.) Today I sensed my 12ax7 tx tube was not behaving properly. I probably spanked it a little hard. I had a 12bh7 but had never played with them before nor did I even know anything about them. I popped it in. "0"! I think I like it!
But I really appreciate the offer and help. Nothing helps with a project more then a willing ham on the same freq. What would you suggest for freq? 29100 or?Band is noisy here but I can listen. Here is the little transceiver.
Don Ve3LYX

[KB2WIG]

Trying around 29.000 is not  a bad idea. Being close to the calling frequency might dredge up a few more comments. If its too noisey, one may always move on down the band.

When du u think u might be on the air?


klc

[VE3LYX]

I dont know what to tell you. This little rig 's modualtor is not going to do the job. It works but that is all. It appeared to work fairly good on the bench for a first try and I figured I could improve it when in the box and all bolted up but never got beyond first success. Tried a bunch of things with it today. I will have to add another tube  and forget the dual modulated triode idea so it will be worked on as I get the urge. The other rig which I am waiting for a new mixer tube for could I suppose be moved to 10 quite easily. The antenna is almost finished. I will see what I can do. It is a pretty decent rig I think and has a bit of Punch for a low power rig. I have to cut back on plate voltage on the mixer tube because I can blow them easily by cranking up the speech amp. that though is about a two minute job. I will see what I can do to get it up and going on 10M. I will post it here.  Listened around on 10m today. Heard mostly beacons , a concept I dont understand BTW, using good space to do nothing. I would like to hear a lot more AM activity .
Don Ve3LYX
The problem is that the oscilator side of the tube runs real strong while the audio side is much weaker. it seems pointles to add a tube to amplify the audio side for a questionable design when I can simply use both sections for Rf and add a simple modulator. To cut back the RF side to give the audio more dominance also seems in this rig anyway counterproductive. HOWEVER I am going down to studio B now to try and make one side a cathode modulator and leave the other Rfso the tube will modulate its otherside. That just requires moving one connection. Might not work but I have zip to lose by trying. (and everything to gain if it works. So dont give up hope just yet.  

[VE3LYX]

Tried cathode moduating using 1/2 the tube to modulate the other side. Drove it with a hastily whipped up carbon mic circuit. It worked to be sure but made the freq wobble. FM ro perhaps FAM. Would work perfect if this rig was a mopa and I was cathode mod the PA. HOWEVER. I tried a lot of things today. I just finished successfully modulating it with a transformerless plate modulation system. Rf power remained as it was and audio could clearly be heard in a nearby monitor rx. It is an initial test but it appears to work. My Dad a EE had told me many years ago about this method and I just took a wild guess at how it could be done. It works. How well, remains to be seen.
Don VE3LYX

[Ed-VA3ES]

Converting disused CB's to 10M is interesting but ultimately  useless.    The problem is the 10 kHz increment.  To be useful, you need  a 5 kHz increment to  properly tune in stations, which in the 10M AM portion are typically about 5 kHz apart.    Go for it anyway, as it is typically an interesting mod.   

Find CB's that are working.  The last thing you need is to work on some radio that has been "Golden-Screwdrivered".   Modified CB's can be quite interesting; they use actual collector modulation for rather excellent modulation.  If the AMC circuit is still intact, you can achieve  over 100% positive  modulation with these radios.   While 4W is rather puny,  you can always drive an amp for extra power. OTOH, when the band is open, 4W will do the job.

A neat radio to mod for 10M is the Johnson Messenger 1 or 2.  This is  a tube-type rig, with discrete crystals.  Easy to move to 10M.   The problem is  that crystals today are quite expensive.   I would add a DDS VFO instead.

[VE3LYX]

I am already looking for a johnson messenger tube rig . Building VFOs is almost a hobby here so I had thought of that too. And then putting in a better final could be fun too. One will show up sooner or later I am sure.
Don VE3LYX