Ok, here's a question for all of you CB and HAM guys out there. I have antenna cables for a dual antenna setup which I had on my last truck. However, I want to just use one antenna this time with a mag mount on the roof. Can I still use my dual antenna cable for the single antenna application? Basically just using one "side" of the dual cable and keep the rest of the cable zip-tied inside the cab somewhere.

If so, what affect - if any - will I have with transmit/receive clarity, swr, ect.

Thanks

 

I'm no CB expert, but I'm pretty confident you can't use a dual antenna cable for a single antenna. Without that second antenna set-up and tuned, SWR could go crazy. At my previous job as a commercial driver I had my CB coax replaced once and the tech forgot to hook up one antenna. My SWR was crazy and the thing didn't work well until they pulled it apart and connected both antennas.

CB cables are cheap, your radio is less so. I'd suggest going out and geting the right cable.

 

Same same. You'll get the red "ANT" light on your CB if one of the cables isn't installed. I just installed dipoles on my truck last weekend.

 

DO NOT run single antenna on a dual antenna cable. Impedance will be all wrong and you risk blowing your radio finals. Coax isn't expensive, just go to a truck stop and get a single cable. Don't go to rat shack .

 

^ What he said.

The dual antenna set up isn't just a cable strung between two antennas. The cable dimensions are such that it acts as a power divider - and phaser - for the signals transmitted/received.

Do you know what a sine wave is? It looks like this ~ . That is what your radio signal is. When you run dual antennas (CORRECTLY) you are laying two sine waves directly on top of each other, or what is called "in phase". When you do that it gives you gain, or directivity (somewhat), towards and away from the perpendicular of the antennas. Draw a line between the antennas and one perpendicular and you have your directivity - twards and away from the vehicle. Notice that this directivity also aligns with up and back the highway you are running (interesting how that works, eh?).

If you phase the antennas 90 degrees out of phase the directivity becomes in line with the antennas in the direction of the latest antenna. If your left antenna is 0deg and your right antenna is 90deg you have directivity to the right.

Note that in any phasing instances the antennas HAVE to be 1/4 wave length apart if you are in-phase or in any other increments of 90deg (1/4 of 360, or a full wave/cycle). Note that 1/4 wave length happens to be about 8.5' on CB. Note where the dual whip antennas are on a semi truck - way out on the mirror supports. Take a guess as to why they are out there....

I know thats more than you ever wanted to know about radio theory.

 

Man, I learned this the hard way. I have "dipoles" but only one of the antennas is actually being used. I didn't know you needed 8' of space between them, until I had read someone else mentioned it as well.

 

You are not necessarily using one of the two.. they just arent working as they are intended, ie - not as good as they should.

For you to be running a dipole the antennas would have to be fed right in the center with the antennas butted up against each other mount to mount with no coax between. The center goes to one and the shield goes to the other (or ground side of the coax).

I have always preferred the single antennas. They are easier. The bigger the more efficient (4' over a 3' fire stick, center loaded whip over a base loaded whip, 102" whip over a loaded whip, etc).