1 antenna

Depends on the truck, but most are using both antennas. Leaving one off would cause the system to be mis-tuned and could harm your radio. Not to mention your receive and transmit range would be severely limited.

If you ran a coax from the single antenna to the radio you would be fine.

 

No, dual antenna is co phase 75ohm coax. To run one antenna you'll need to run single 50 ohm coax to the antenna. At least that's the way I understand it.

 

Actually nearly all modern trucks use splitters not 75 ohm coax. But the comment by n9mqx applies to splitters also, as well as a dual coax. You must run two if it is designed for two. Either that or take the advice of Luwi67 which also would work. Bottom line is you must have a low SWR.

 

and the antenna on the passenger mirror on some trucks is used for the stereo.

 

and if you take that antenna off then it messes with the CB also.

To the OP, if the truck is setup for two antennas then you MUST run two antennas. The only way to go to a single antenna setup and keep your Cb from burning its final transistor is to install a coax meant for a single antenna setup. Well you could use the dual coax setup but you would have to find a dummy load for one of the coax leads. It is cheaper to use two antennas.

 

Which would also rob half the power from getting out, i.e., the power dissipated in the dummy load as heat. This is not the same thing as that incorrect statement drivers are always saying the CB guy told them about duals. That is, one antenna robs half the power of the other in a dual setup. Simple study of interference patterns would show unless the interference is 100 percent destructive between the two then no power other than dissipation is lost. Of course at almost 9 feet apart the interference is more constructive on a typical truck. This is unrelated to Rat's comment; just a good place to bring up my pet peeve of hearing that comment about dual antenna systems. Seems I hear it a lot.

 

I have never had a dual setup work as well as a single antenna that is tuned just right.
Only one antenna and one length of coax to worry about too...

My truck came with duals and cheapo fiberglass antennas......gone the first couple weeks..

 

I had a dual set-up on a 88 Pete that worked really good. But, that was a long time ago.