Coiling coax does make for an RF choke. But that's not bad, it doesn't affect the signal -inside- the coax, it only 'chokes' RF on the outside of the coax which you don't want anyway.
- 'Doc

WHY would someone coil up "excess" coax? Cut the cable to the correct length to reach, TUNE the Gosh-darned antenna to resonance and for-GET about all this coax nonsense!!! If we are using coax to "tune" the antenna, then we don't NEED the antenna at ALL!!! Coiling up coax is another of these myths that become radio "gospel". We DO need the antenna, however, because it DOES more efficiently RADIATE the signal out into the air.

It is difficult to explain WHY we are having this problem on a forum. It involves several things that are difficult to explain. For a number of reasons, the antenna is not matching and it usually involves something called impedance. It can be caused by 1) insufficient ground , 2) improper mounting, 3) the antenna itself too short or long (NOT the coax). Is the antenna too CLOSE to the body of the vehicle? Is the body PLASTIC? Has the antenna itself been broken in some way (whacked by an overhead)?

If the antenna itself is OK, the mount is correct, the location is good and the system STILL will not "tune", then there are several solutions. I would highly recommend finding someone with an MFJ Antenna Analyzer that will read SWR and IMPEDANCE. By attempting to set the SWR while observing the IMPEDANCE, you will get an picture of what issues are present. If the antenna won't come into resonance and/or the meter won't read 50 OHMS, then you'll have a clue as to what's going on. Sometimes you can wind a small coil or use a small resistor(just a few experimental turns will do) and put it in series-series parallel at the feedpoint of the antenna. This MAY provide the correct impedance and present an acceptable SWR.
I know this is a complicated solution to what SHOULD be a simple problem. Normally, at 27 MHZ, such measures are not necessary. But, again, not knowing exactly HOW the system is installed.................................

Good luck with it.

CWM

Is'nt that what wind the coax in a coil does.lol leave to theory to complicate the most basic of CB lore.

No. We are confusing a RADIATING coil with a device at the FEEDPOINT of the antenna that is used to transform a random impedance to 50 ohms. This device can be a little coil, a capacitor---even a resistor---- OR a toroid that is installed from the base of the radiating element (bottom) and taken to nearby ground. I don't want to get into a complex explanation of antenna theory, but what we are getting into is the mechanics of impedance. First of all, remember: RF ground is NOT necessarily DC ground. It CAN be, but often is not. That's where we must "fashion" a potential to ground that results in a 50 ohm path from the antenna to ground. I know, it doesn't make a whole lot of sense to those who may be new. This is where an antenna analyzer comes in VERY handy. Usually, at 27 MHZ, this is not necessary, the general rule being that the higher in frequency we go, the less we have to monkey with feedpoint impedance. This gets into the various values of resistance (feedpoint, radiation, and coil [if any] ) that are present in an antenna system. I don't have time to do that right now. After all, we have gotten off topic a bit and it won't help the fellow with his issue.

A coil that is IN the antenna itself is there for ONE purpose. It does NOT make your signal BIGGER or BETTER. It is there because the antenna is too LONG, & it has to be shorter due to physical limitations or height restrictions. In the case of lower HF frequencies (below 27 MHZ), some mobile antennas would have to be 60 feet long!!!! We can't have that!

CWM

where is the ant. mounted? is this on a big truck or a pick up? if it's on a pickup the ant. needs to be mounted so that 2/3 of the ant. is above the cab. otherwise you can get a lot of reflection and i believe you will have high swr's.

__________________
just a countryboy from wisconsin

mobil rig: cobra 29 peaked and tuned and a 2sc1969 final, astatic 636 mic, 102" whip.