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CB radio problems...

949 views 8 replies 4 participants last post by  Maverickxeo 
#1 ·
On my 94 ZJ, the PO installed a Cobra 25WXST CB radio, and he used a mag mount antenna. I never used it (SWR was too high) and I finally go around to buying a 4ft firestik, and a firering 18' cable.

I mounted my antenna using a 3/16" piece of steel, attached to the rear body, under the bumper pretty much right under the most forward part of the tail light on the right hand side of the vehicle.

No matter what I do, I cant get the SWR down past 3. Ive ran an additional ground to the antenna, Ive ran the CB radio straight to the battery (ground and power) but nothing I do makes a difference.

I DID however, notice that when I 'touch' the radio, it causes its built in SWR to move around; and my mic makes a sort of 'whine' noise when plugged in (and engine running; engine noise I believe) and if I move it around, the SWR moves.

Any ideas?

I should also mention this is my third vehicle Ive installed/set a CB on... (I did my dads and my TJ).
 
#2 ·
SWR up around 3.0:1 should make one suspect that the antenna mount is either improperly installed, or there is a problem with the mounting location or mounting method. The antenna mounting stud must be properly assembled and the mounting bracket must have a clean and solid connection to the body. The changes you notice when touching the radio also should make you suspect antenna mounting problems or perhaps coax cable assembly issues. I have never really liked the FireRing.
 
#3 ·
SWR up around 3.0:1 should make one suspect that the antenna mount is either improperly installed, or there is a problem with the mounting location or mounting method. The mounting bracket must be properly assembled and the mounting bracket must have a clean and solid connection to the body. The changes you notice when touching the radio also should make you suspect antenna mounting problems or perhaps Coax cable assembly issues. I have never really liked the FireRing. Damaged or faulty wires in the microphone wiring or mic plug can cause issues.
Thanks for the advice.

I did some troubleshooting with my father, and I hooked up the mag mount to the radio, using the 3/16" steel bracket I made, and I was able to get about 2.5 SWR. I assume this is because the bracket is better grounded as the antenna has a much larger base.

I swapped the radio into my TJ (with a good antenna setup) and it was fine; I swapped the antenna from my TJ to my ZJ and it does the same; so its either the mount (most likely) or the antenna.

The steel does have a mill scale on it, so Ill try to remove as much of it as possible and see if that works tomorrow.

I am pretty confident it was the mount... for the record, it is 3/16" x 2" steel that I bent at a 90* with 4 self tapping screws to hold it to the body of the ZJ, right under the passenger side taillight; under the bumper cover. Basically, something like this:

https://www.google.ca/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&ved=0ahUKEwil3Pi7oIHNAhUN8GMKHSrfCXQQjhwIBQ&url=https%3A%2F%2Fwww.youtube.com%2Fwatch%3Fv%3DpGQ1bKmVHOs&psig=AFQjCNEaOZ_wE_BY2H7ewyqIY9LYtclQyA&ust=1464678955458134
 
#4 ·
Excellent troubleshooting, that really narrows it down. The antenna stud needs clean bare steel to mate up to. The bracket and the Jeep both need to be clean bare steel to mate up to. I like to use star washers from the hardware store on the brackets fasteners. The rest of the bracket can be painted.

.
 
#7 ·
Check the physical connection from the PL259 at the antenna. If the sleeve where the center pin is out of spec, the center pin won't make good contact and cause a high SWR. Just went thru this where I had a bad right angle connector.

If using the fire ring, make sure it has bare metal for the ground to ground connection and the center conductor makes a good connection to the stud.
 
#8 ·
Let's try this:
Disconnect the coax cable from the back of the radio (leave the other end connected to the antenna)
Set your volt/ohm meter to ohms
Connect the black lead from the volt/ohm meter to a good vehicle ground
Touch the red lead from the volt/ohm meter to some other good ground - s/b 0.00 ohms (s/b = should be)
Now touch the red lead from the volt/ohm meter to the outer ring on the coax cable - s/b 0.00 ohms
Now touch the red lead from the volt/ohm meter to the center conductor on the coax cable - s/b a lot of ohms or showing no continuity. If it's showing 0.00 ohms or close to that, you have a short somewhere and you're using the vehicle as the antenna which is undesirable.

Doing this checks the coax cable and the antenna/mount.
 
#9 ·
Forgot to update (was sick a few days...)

I managed to get it down to about 1.5SWR on channel 1 and 40 finally... the ground on the firering was not making contact. I had to redo the mount as the plastic spacer on the firering wasnt 1/2" like it shouldve been; it was slightly larger. I was able to get it to ground properly by just rounding out the hole slightly.

Thanks for the help though! :D
 
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