Cobra cam 89 - modify it to talk on channels 24-40

[kingfish66]

Ever have a Whiteface or Blackface Johnson cb with 5 or 10 channels to plug in the channels you selected? Why not the same with the Cobra Cam 89 and possible other "plug in type" 23 channel cb radios.  I did it with the Cobra Cam 89 by replacing the 23.340 crystal (ch. 5 - with a 23.590 and replaced 23.440 (ch. 13 - 16) with a 23.640.  I expected to pick up channels 25 - 28 and 29 - 32 with this but to my surprise I actually got channels 26, 27, 28, & 30 on the 23.590 and then I picked up channels 31, 32 33, & 35 with the 23.640.  WHY GO TO ALL THAT TROUBLE WHEN I CAN BUY A 40 CHANNEL RADIO???  For one thing you cannot find a quality NEW base radio in todays market unless you want to pay a war pension and then they are fully loaded or are geared toward 10 meters and "uppers and lowers" which some of us have no use for.  Second you are limited to only two or three mfgs. of these radios (galaxy & rci).  And thirdly it is not hard nor expensive to obtain these crystals to eliminate channels you never talk on or listen to.  Simply unplug the old crystals and plug in the new, works just like the old Blackface except you have 23 channel spaces to tinker with and you replace 4 channels with one crystal...  If you have a great old Cobra Cam 89 or other base radio with plugin crystals and have a channel or two you like to talk on above ch. 23 give this a try.

[Train]

Lemme do some math as it has been 35 years since I did it to a Cobra 29A, but there is a way to add a crystal to the NB switch and give you 23 more channels above channel 22, or 23 or wherever you want to go...... (It'll still have the "A channel" gaps, tho.....)

It all has to do with switching the 11.275 (if I recall) crystal to different value crystal on the NB switch. There are three different sets of crystal used on this board and the way they end up on the desired frequencies is by adding two and subtracting one. (zat rite?)  

The 455 Khz gap bewteen the TX and RX plays a part, as well. Now, I'm really lost!!!

Hopefully, someone will chime in that knows what I'm trying to convey and beat me to it. Hopefully......


Oh, Nomad!!!!!
 

[Warbird]

Oh, Nomad!!!!!
 

I could see the wheels turning and jumped to the end because I knew how it would end.

[Tubeman]

The cam 89 uses a different mixer crystal for tx and rx. So one crystal swap wouldn't do the trick.  A VFO or crystal box worked for those old radios. Ever see one of those little crystal boxes, they even made one that matched the old Johnsons.  
Like the OP said, you get four channels for each crystal swap.  I have put a  multiple position rotary switch on the back panel to mount the crystals on.  Lot of different ways to do it.

[kingfish66]

Just curious, does anyone reading know where to obtain or how to make one of those crystal boxes or vfo's for the cobra cam 89?

[Warbird]

Just curious, does anyone reading know where to obtain or how to make one of those crystal boxes or vfo's for the cobra cam 89?

Check E-bay, there are some listed on there, search for Crystal Extender.  I think this is what Tubeman is referring to.