Help with Cobra 29 SWR/Antenna Light

You would be wise to have it checked with a proper SWR meter. It could be something as simple as a poor ground. Where did you mount the antenna?

 

Ideal place to mount antenna on bed is about 2ft behind cab. You can get away with mounting right behind cab sometimes, but in all the instances I can remember the antenna used was 4 - 5 ft long. So if you don't want to spend anymore money, first use a good SWR meter or antenna analyzer to see where you are really at and then go from there. It won't cost anything but time to move the antenna. FWIW, even if you get a good SWR reading out of your 3ft antenna, don't expect great performance from it. Like a lot of things in life, when it comes to mobile CB antennas, longer is better. Also, running a ground wire will not overcome the lack of an RF ground. If you determine no matter where you mount your antenna on your bed, your SWR is still high, it is because your bed is not grounded good to the rest of the vehicle. A simple ground wire will not solve this problem. Braided ground straps are the answer. The wider the braid the better. I would first try (because it's easier) a braid strap from the bed to the cab. Be sure and shiny up the metal where you connect. Once your connections are determined to me permanent you can spray them with paint or some undercoating stuff to keep them from rusting. The other choice that I have seen work is a braid strap on each corner of the bed to the frame. Good luck, this stuff is mostly trial and error, but if I was going to go to this much trouble, I would want a 4 - 5 antenna. However if you get the 3ft antenna all matched up good you should be able to go to a longer antenna later without any problem.

 

Do not trust the built in SWR meter. It is good for a reference only. i.e. get a good meter and check your SWR. When it is adjusted where you want it, check the built in meter to see where it is at. That will give you some idea of where your SWR is at without hooking up an SWR meter. The meter in the radio can go out of adjustment fairly easy however. It is not a good idea to trust your radio to a "built-in" SWR meter. It should be checked regularly (every six months or so) corrosion and loose connections can change it very easily. If your lite is coming on you most likely still have too high of an SWR. I haven't talked on a Cobra in a while. I forget what the lite is supposed to do when you key up. Don't worry about the lite if the SWR checks good with an independent meter.

 

ChickenChops, before you start spending a whole bunch of money on trial and error stuff, go to a good truck stop where there's a CB shop and talk to the guy. It'll be much cheaper in the long run if you let them take it from there. I say this because I have the cheapest little Midland CB money can possibly buy...I also have a dual Wilson 2000 antenna set-up done by a CB shop guy. It works better than anything I've bought yet.

 

That's good advice if you don't have access to a SWR meter. (and know how to use it.) Your point about a good antenna and cheap little radio is also correct. The biggest, fanciest radio in the world won't overcome an imperfect antenna set-up. I re-read his post and the part about the needle jumping when he starts his motor tells me he needs to find somebody with a little CB knowledge to give him a short lesson on how the thing works.