Hooking up antenea on Freghtliner Columbia

Last things first -- co-phasing is largely for aesthetics in most applications, as it's hard to get two CB antennas sufficiently far apart to affect their collective radiation pattern to any benefit to you. Mostly co-phased systems only benefit the antenna & phasing harness vendor.

Stock coax in most trucks, especially the ones that have a multiplexor behind the dash and distribute the TV, Be-bop radio, and CB all to a port somewhere and work off of one or both antennas.

Conventional wisdom among the Illuminati of Ions seems to tend towards abandoning whatever is in the truck for your CB, then go buy a single decent antenna (as tall as will fit on your truck), with its own, *new* coax, and a mount to hang it off either a mirror bracket or a hole mount in the middle of the roof. If your roof is Fibreglas®, then you can drop the headliner and either paint the underside of the entire cab roof with electromagnetic shielding paint (like what's inside of the control cavities on electrified guitars & basses), or several runs of sticky copper or aluminum tape, going as far to the sides and down the A- and B-pillars, then putting your mount right through the roof *AND* through the place where the tape runs all overlap.

AWS lamps can also illuminate if some Golden Screwdriver From Hell has done naughty things inside your radio, trying to strangle every last 1/100th of a watt out of it, and generating massive amounts of spurious and/or harmonic energy which will reflect from the antenna and indicate as a poor SWR.

Also, as to the age of your existing antenna, since it looks old, it could very well have a crack in the windings around the Fibreglas® fishing pole in its center, if it's a 'glas whip, or a cracked nylon insulator where the whip screws down through the mount can cause the driven element (whip) to ground out, playing havoc with the match.

If you're not really too familiar with this stuff yet, *and* if you don't have access to any known good antennas to test with or external SWR meters to check things with, I'd suggest that, just for this one install, you go hit up a competent radio shop (a commercial shop will *probably* have more and better test gear than a TS CB-only shop. Ask if you may observe what they do, as you'd like to be able to learn enough to maintain your gear on the road and understand what goes into a proper installation and a logical test routine. You'll find you can do an awful lot by approaching things logically, but not until you've got a small yet critical mass of info on how what goes where & when.

You'll find that an outboard SWR meter and a dummy load with the appropriate adapters and jumper cables will be invaluable to keep around, and should cost you ≤$100. An antenna analyzer would be the next step up, but at over $250 for decent ones, they're probably superfluous for a gentleman who's only going to be messing with one antenna system typically.

Hope that helps. If you need more info (I usually err to the side of brevity) feel free to ask. I'm a commercial tech with a commercial lab and I frequently get the opportunity to help folks out, either here or in person. But there are many more and better brains on here than I am, so you certainly don't have to rely upon my advice alone -- I just happened to be the first lad who spotted your question.

73 & good luck with your project.

 

Well there should be some receiver noise with a phased system even if there is only one antenna.

I’m not there so I can’t tell beyond a shadow of a doubt that it’s a phased antenna system but most likely it is.

That being said I still say that if you have one good antenna you should be able to hear something. Are you near a highway that has a lot of truck traffic I only ask because if you are somewhat isolated you may not hear much but even at that you should have what we refer to as “GROUND NOISE” this is just static level noise without anyone talking. Make sure your RF gain is totally clockwise if you have one and volume up and squelch off. also you may try the same thing with just touching the center pin in the back of the radio with the center pin of the connector. You could also just stick any kind of wire in the back of the antenna jack a piece of hookup wire with one end bare and touch the center of the SO239 “antenna jack” on the back of the radio all I’m trying to do is establish the fact that there is some noise being generated when a there is a wire of any kind hooked up to the radio. It won’t hurt the radio just don’t transmit while doing this. And of course if you can try an antenna you know is good that would be a good test as well.

 

You may want to look at the kick pannels by the doors just under the dash. Columbias use sections of CB wire connected together. The wire starts at the CB mounting and split and go through to the door post and then go down to the kick pannels then through the door to the mirror. The connectors sometimes come apart under the kick pannel or in the mirror head.

Hope this helps.

Duke