I've tried 2 different cb's in this Mack with no luck.

Here is a good place to start.

 

Sounds to me like a shorted antenna installation, if you installed a co-phasing harness incorectly you probably now have two shorted antennas, follow the assembly directions for the mounts exactly, if you put the insulator in the wrong place your now grounding out your antennas. equals no or poor rx tex

 

Please explain how you install and apply a cophased coax.....
Onmy way is to use 1 ant on a cophased coax...
Based on pic his insulator is correctly placed on top....
He "DID" say he pinched his coax....

 

Yeah, once a "pinch" is suspected, it takes the number one place in the lineup of usual suspects.

 

cant really disect it online. check everything, start by removing antennas ohm out antenna line end to end then shield to center conductor, center to shield should show open, if this is good then connect antenna(s). check swr.

 

why would you use a co-phasing harness on a single antenna. makes no sense.

 

Thats my point..I was askin how its done cause of the way it was said by poster..
Ya dont use cophase on a single ant..

 

Here you said if he incorrectly installed a cophased coax....So im askin how do you incorrectly install a cophase vs a non cophased coax??

 

If you have a shorted coax, it does not matter if it is co phased or not.

The important things are not shorted , clean secure connections, not pinched.

The isssue is not if theres one or two antennas, it is trying to help the op with the problem. IIt is also possible that something else installed in the truck maybe the problem, may not bbe a antenna problem at all.

 

Go to a radio shop and pay the 50-60 dollars. They will get you "tuned in". I went to Big Rig Radio in Phoenix. Fantastic job. I paid 120 but he mounted it repaired some broken ends. Cut the metallic paint on the mirror away from the antenna and tuned it. Works great