[frhalevt]

I installed a CB in my 2004 TJ Sport in a Tuffy single overhead console. I installed a 6ft antenna on my rear bumper and have been unable to get good SWR. I had a local radio shop attempt to get the SWR lower and they were somewhat successful. The shop said I did not really have a good ground plane. My ground on the antenna is good but not the ground plane.

I read on the internet that I would be better off if I moved the antenna mount higher on the Jeep. They also mentioned using a no ground plane antenna.

Any of you HAM/CB radio gurus had any experience with a no ground plane antenna? Are they blowing smoke and I am just going to have to live with less than desirable SWR?

Thanks,
Frank

[shookwell]

Bumper is one of the worst places to put a CB antenna. Try a mount that goes behind the taillight, a spare tire mount, or mounting on the body itself. Also, make sure you used good quality coax.

[Scrambler82]

This is wordy, sorry.

These are my thoughts on it.

No they aren't blowing smoke...
Word has it, in the theory areas, that a 1/2 wave antenna requires less ground plane than other wave length antenna, i.e. ¼ or 5/8 WaveLength.
Let see, a CB Frequency Wave Length is approx. 36 feet long, so a half wave antenna would have to be 18 feet tall; I don't think you want to have an 18 foot antenna on your vehicle.

The ground plane is important; it will actually direct the strongest transmitting and receiving point on the vehicle but grounding to the vehicle main ground system (the frame) is more important.
I would check the grounds on all of the pieces of the system, the most important being the antenna mount.

What was your SWR reading; 1 to 1.5 is OK; even a little higher would really hurt but the closer to 1 to 1 the better.

Since the radio/antenna/coax are already installed you will have to backtrack all the ground connections. Make sure they are connected to bare metal.

Did you get the Coax with the antenna or purchased separately?

How does the coax attach to the antenna mount?

Is the radio grounded other than with the black wire, I mean an additional wire from the back of the radio to a metal ground?

Run a ground wire from the antenna mount to the frame.

Make sure your antenna mount is install correctly, there is a fiber washer that needs to separate the center connector of the antenna/coax from the ground or mount.

Then adjust the SWR of the system and work form there.

Take you time, Later,

OH YA, I don't know if there is such a thing as a good location on Jeep to mount the antenna.
If you have a Roll Bar and it is grounded really well, and you don't run a top, mounting the antenna on the top of the bar, centered on the vehicle would proably be best but not always practical.
Best thing to do is pick the point you like the best and work with it.

Luck,

[wb2jte]

yea, what nnf said. You didn't say what kind of antenna you have, a full size 1/4 wave with the big spring on the bottom? SWR souldn't affect your recieve ability much, just your transmit power. The antenna is 1/2 of the 'antenna system', the body is the other 1/2. One should be over the other. If your antenna is on the bumper and most of it is right next to the body, 1) it will be very directional 2) wont get a good match (swr). I would say to relocate the antenna, higher, or maybe a mount on the hood. If great performance isnt neccessary, just to yak with the other 4x4 in front and behind you while off roading leave it alone. Ground is an important issue, not from a dc power viewpoint, but an rf issue. A good ground at the antenna base.

[ecrab3]

I really only use my CB in trail runs, at most we are 1/2 mile apart from each other and my swr is sky high! If that is what you plan on using it for, I second the leave it alone suggestion.

Yes, there are such a thing as no ground plane antennas, look at marine antennas, they are made to be used on fiberglass boats.

Higher on the Jeep is better but I think if you can get out atleast 500', and your with a group, thats good enough....maybe best your gonna get. Keep trying! Add more ground wires to the antenna mount to a bare steel area, might help some. It did in my case. But im still in the high 2s on my swr, been that way for some time.