CB Blues

I'm curious about the VSWR as well... How did he attempt to tune the antennas??? If I remember correctly, on a Co-Phase system, you must tune each antenna individually with a 15ft jumper cable...

 

With my experience, when you move an antenna closer to a metal cab and the swr is better, or if you move the antenna forward and things improve, then you are dealing with an RF ground issue.

 

I would try to "bond" the door to the cab. The mirrors are mounted to the door and I'm sure it's not going to be a good electrical, or rf, connection after all these years.

A cheap and easy test would be to just find a "ground wire" from the antenna mirror bracket to the cab. Any ole wire will work as a quick cheap test. Then maybe you can hunt for some wide ground straps to replace the wire.

 

If it was an RF ground problem, your SWR readings would be very high. I don't get what is going on here. Have the cb radio output checked by a competent tech. Is it possible that the radio has been detuned to work with an amplifier? Has the radio been run previously on a truck with excessively high SWR and the finals (final amplification circuit) been damaged?

 

If your running two ant are you useing 2 50 ohm coax with some sorta 3 way connector or a cophased 75 ohm coax.1st what i would do is try 1 ant and 1 coax @ 50 ohms...
Run ant as far away from cab as possible on mirror arms...Start some bonding straps....
Keep them as wide but as short as possible..
Is there any mirror arm connections that have thread locker or plastic bushings between each mirror arm connection point..
Swr doesnt tell you what ant is sending out it just tells you whats happening between ant and radio..
What type of ant stud are you useing and is the center pin of the coax makeing a good connection to female side of ant stud..
You got those big stacks that could be affecting things to so maybe lean your ant no more than 45 deg..

Get out your multi meter and start testing 1st to see if your trk and ant brackets are connected for rf travel..

 

Jj.....Doubt he will wanna put a pair of 7 footers on a 379...He would be taken down fighter jets @ 20,000 ft..lol

 

Honestly rob....
Unless your puttin out mega watts i wouldnt bother with those coiled type ant...Stick with a top loaded fibreglass ant...
If you are goin big power im partial to the predator.....Single coil comp with a short shaft @ a 45 deg lean....Be sure you use a hd stud and dont go with that chrome studded crap..
Personally i like the wilson hd alumium stud..Make sure ctr pin of coax makes a good connect with the head of the stud bolt....I discovered mine wasnt and had to coil up a single strand of copper wire approx 1/2" long to stuff the head of said bolt then screw in my coax to get my stuff to work well..I could hear the diff and saw the diff when i hooked up my analyzer..

 

Whats the point of tuneing each seperately with a piece of 15ft coax when he will need a a lil more than half that per side..
The coax you use to tune seperately need to match whats installed..
Thats like tuneing your lambo with a ford escort engine but putting in a v 10 turbo for race day..
50 ohm coax for single ant and 75 ohm for cophase..Cant mix n match length and ohm coax..