On Thu, 3 Nov 2011, Padraigh ProAmerica wrote:

Just acquired from an old lady her old CB transceiver. It's rather old;
crystal controlled. Is it feasable to swap out the 27 MHz crystals and
replace them with 10M crystals? Is there a source for these crystals?
And would any major modifications to the rig be required?

So long as it uses a pair of crystals per channel (or one for transmit and
a tuneable receiver), those are the easiest to convert. Just change
crystals, and maybe a slight realignment is needed.

Of course, there was a period when the CB sets were synthesized but via
multiple crystals, mixed together. Those would require more effort to
move to 10M, one would have to figure out what was going on and then
recalculate, and likely realignment would be more important/difficult. I
don't recall anyone writing about converting those.

But if there is a pair of crystals per channel, all you need is to either
scrounge up suitable crystals or go to a crystal manufacturer with
information about the CB set, and they'll grind a set for you. Maybe
costly at this point.

The transmit were usually overtone, the actual frequency being around
9MHz, the receive crystals would be the signal frequency minus the IF
frequency (often 455KHz, but some had a higher IF), and they too were
usually overtone crystals. The good thing is that since you're moving it
to a ham band, you can pick any frequency within the band, the bad part is
that some parts of the band are better than others in terms of activity,
especially for AM, and you need to find a pair of crystals for the
frequency.

There was a period when CB sets often had a tuneable receiver, either with
a few crystal controlled channels for receiver or none at all, and those
would be best, since you can then find any crystal that works and provides
a useful frequency, without having to worry about the receive crystal taht
also has to be the same frequency, but with the offset for the IF.

Michael VE2BVW



Any info would be appreciated (and yes, I hold a Technician
class license).

--
"History is not a spectator sport."-- Dr. Bruce Freeberg --