> I know others have done it before...but I would like
 > to know if anyone there has modified an 11 meter rig
 > (specifically a Johnson Messenger 123A) to 10
 > meter use.
I'm sure it's been done before, and I'm sure someone who's had that 
experience in here would be glad to help you.
 > I have just inherited this rig, brand new, in the box,
 > never used...I have little use for 11 meters, much less a 23 channel
 > radio...but I *could* put a 10 meter radio to use.
I'm not familiar with the 123A - have you opened it up to see if it's 
completely crystal controlled, or crystals in a PLL circuit?
 > Does anyone know, definatively, the practicality /
 > legality of doing such a mod, as well as how to do it?
Ham Radio (at least in the United States) is the only facet
of the communications medium that does NOT require that your equipment be FCC 
type accepted.  This means you can "roll your own", or modify a peice of gear 
to work within the HAM Bands, and within specs.
It's completely legal to modify a 27MHz radio to transmit in the 28MHz band, 
and you may even operate it, if you are so licensed.
73 = Best Regards            -Jeff KA5THB
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