The Defpom Forum, for RadioMods, S&M Software and Music by The Defpom

I've got a mid 70's Cobra 135 base that I'd like to use for SSB Dx. It's a 23 channel radio, and has really good sounding audio and a great receiver section. I'd like to use it on sideband, but most LSB calling happens up on channel 38. This presents a bit of a problem on a 23 channel radio. I read somewhere that there was a crystal and switch mod for the 135 that would give it full 40 channel coverage, but I can't find detailed information on it anywhere. Would anyone happen to know of a channel mod for this rig?

Because it is a crystal radio instead of a PLL based one it complicates things a fair amount.

I suspect that it MAY be possible to instal a crystal mixer PCB, to shift one of the frequency banks to another range, to give higher channels, but it is not something I have done on a crystal radio, so I cant be sure, my suggestion is to take a look here: http://www.cbcintl.com, however, the super expo no longer appears on the site, so it may have been discontinued now...

I found two mentions of the mod elsewhere on the internet, but no information on installation was given.
http://www.worldwidedx.com/cb-band-cb-r ... #post23032
http://home.ptd.net/~n3cvj/cobra135.htm

Crystal sets are not my area, but I do know that there are two versions of the 135, I have a diagram for one of them, and that version (which may or may not be like your one) does not give any easy way to add more channels, yes there is one crystal that can be switched but it will only work on RX, not TX, so that is not much good.