Jimmie:

SWR is a direct measurement of impedance mismatch. If you change the
coax length, thereby changing the angle the coax is conducting, and
the SWR changes, then there is something wrong with the antenna itself
that needs to be fixed.

Physics dictates this. There's no way around it.

Coax Length DOES NOT MATTER for a single antenna setup. Period.

-SSB

Jimmie wrote:

wrote in message
...

On Wed, 03 Nov 2004 01:59:15 -0800, "Guntier C."
wrote:


I received and old wilson 1000 mag. mount and want to put it on my quad
(4 magnet) mount. I hear that I need a 18 ft. piece of coax for a
counterpoise. Is that true? Any info appreciated.

Thanks,

G.C.


I'll get slammed for posting the correct answer but what else is new.

Manufacturers of Magnetic mount antennas recommend keeping the
original length of coax.( Wilson, K40, RS, Antenna Specialist, ect.).
Why do they do that? The answer is simple. They realize that there
is no such thing as a perfect or exact scenario for an antenna
installation. They know that in a typical installation of their
antenna the coax length will most likely come into play and can
be beneficial. It can be beneficial in that typically the radio will
see a better load with the manufacturers recommended coax length.

It's not that these antennas can't work with any length of coax. It's
just that in most cases you'll get better results with the recommended
length.


Agreed with tnon. As soon as someone mentions about using a certain length
of coax with the CB antenna someone always asssumes it is to adjust SWR. It
will not do this. It will change the impedance the radio sees which is not
the same as changing the SWR. For example if the impedance of the antenna is
25 ohms 18ft of coax will make the antenna appear as 100 ohms at the radio.
SWR will be 2:1 reguardless of the length of the cable. AS most radios are
antennas are installed plug and go without benifit of tuning and most all CB
antenas represent an impedance lower than 50 ohms antenna manufactures
typically reccomend the 18ft coax for best results under these conditions.
Most radios work better if they are mismatched above 50 than below 50. This
really becomes noticable if SWR is around 3:1. Not uncommon on a typical
plug and go installation. Otherwise length does not matter much on a well
tuned and properly installed radio and antenna.