Nakedginger

Hey, I have a question specifically with shortening a cb antenna. I installed a cobra LTD 29 classic and once it was installed I tested the swr and found, according to the corbra website on how they interpret the swr readings, that I need to shorten my antenna. I have a fiberglass antenna and instead of chopping off the top little by little, I was wondering if I could cut the coax back a little to "shorten" the antenna.

ericfx1984

Ok so on the lower channels your SWR is lower, and on the higher channels your SWR is high right?

take note of your SWR reading at channels 1, 20, and 40

only shorten the antenna if the SWR is low on the lower channels, and high on the higher channels

As for shortening the coax, no that is not going to take care of it. Take the plastic cap off the top of the antenna, then trim it back 1/8" to 1/4" at a time, after each cut replace the cap and recheck your SWR on 1, 20, 40

if the swr goes down on the upper channels then you can continue cutting your antenna UNTIL channel 20 is 1.5:1 or less

keep in mind some antenna just will not tune very well

what antenna did you get?

Nakedginger

Yes, the lower channels have lower SWR and the upper channels have a high SWR reading. I've heard of the small cuts to the end, I was just wondering if that could also be attained through cutting the coax. I have a older fiberglass antenna. It is constructed with a central core with the wire and a fiberglass wrapping surrounding the outer portions. It does not have any visible wire rapping around the outside like some fiberglass antennas. Sorry I don't know the technical name for it.

ericfx1984

just trimmer it with some garden shears or a knife or whatever

RememberTheMallamo

With fiberglass antennas, the price difference between cheap and quality brands is too little to not just go for quality. Get a Wilson or a Francis and chances are they won't even need tuned and if they do it will be minutely. I'm a manager at a truck stop and we've got ****ty Diesel and Barjan brand antennas for like 7-11 dollars while Wilsons are 12-15 and Francis only 13 or so. I of course don't know your situation as far as spending more money but a quality antenna makes a world of difference.

ericfx1984

You know Barjan owns and makes Wilson now...

I am the guy all the locals send their radios to for work and tuning, heck some guys even ship radios to me for work

But honestly from a guy that builds antennas, I would have to agree that there are many reason to drop a little extra cash, but in most situations fiber glass antennas are coiled, and coiled antennas just suck, no other way to explain it, ain't nothing like a 1/4 wave 102 whip, nothing in the mobile world can compete, nothing even comes close

RememberTheMallamo

Where did you hear Barjan owns Wilson? I spoke to one of our vendors just last week and according to him, Barjan went completely under. I also have to disagree that coiled antennas "just suck". You are right about a full length whip, nothing will perform like it, but coiled antennas do work and some work quite well or else they wouldn't bother making them and making so many. Clearance is of course the main reason for coiling in the first place but I sure as hell have never seen a water-cooled 102 whip or a magnet mounted one. Coiled antennas are just as good when you factor in options and sizes as the whole package to consider.