Mcrib

I'm installing a cb in my 91' and am having trouble with tuning the set up. ?I can set the swr on the radio and the antenna with the truck off but when the trucks started the swr is way above where it was with the truck off. Does anyone know what could be wrong or if anyone has encountered these problems when installing a CB radio in these years of trucks

Aktech

It has been awhile sense I ran a Cb,remind me what is the swr is. But i would say the plugs and plug wires. They also made a noise filter for them also.

Mcrib

The swr is the standing wave ratio. Its supposed to be under2.1 on both channel 40 and channel 1 but right now its above 3. I have also checked the wires and plugs and they tested good

Aktech

Are they resistance plugs? And 9mm wires. Tune the antenna one way or the other to see if it helps.

Aktech

Are you running single or dual whips? I always ran single. Doubles most of the time you can't get them far enough apart. Radio shack should still have noise filters.

Atomic Monkey

What kind of antenna setup are you using? I always had problems with mirror mounted whips. Even when I had 2 whips, only one was hooked up. The swr fluctuations you're seeing could be caused by having more power when the truck is running, and/or the EMI from the ignition. I've even had it where I was tuning an antenna, closed the door when I thought I was done, and had everything change. I found out that making sure the whips put the loads above the roof of the truck by a decent distance helped.
I dug up this link for coax http://firestik.com/Tech_Docs/coaxtalk.htm , I remembered sometimes the antenna cables cause problems too.

Mcrib

My setup is a 3 foot firestik tuneable tip antenna with a road Pro 12 foot coax cable. For the mount I just used a piece of angle iron and a cheap stud from RadioShack

Atomic Monkey

Wish I could offer some more insight. Sometimes it could be a ground issue, and other times its where the antenna is mounted. I never really cared for firestik, my favorite antennas where the 102" whip, and the Wilson 1000.

fordtrucknut

i'm running a 102" whip, along with a galaxy 959 radio. and a 450w heater box.

for some reason our trucks are bad with cb signals,.
I fixed about the same problem you have.
FIRST run another ground wire off your battery to the frame, then another one from the cab to the frame, and a third on the bed to the frame.

next get rid of the 12ft cable, you want at least an 18ft strand. some call it a myth, but It worked for me. you can hide the extra cable, make sure you loop the extra cable in about a 12" circle, DONT just bunch it together.

next get you an actual swr meter, the one from the shack is fine.

LAST AND ONE OF THE MOST IMPORTANT
go somewhere along the highway where it is pretty rural with no tall buildings, no radio towers/cell towers, and no power lines.
when you find and area tune it from there.

Mcrib

Alright I'll give that a try