I'm one of those who believes coax length is a bunch of ^&%#. I NEVER even consider "coax length" in an installation, and I've been doing installs since 1965! Never even HEARD of such a thing.......until I heard it from a CBer. And I
rolled in the floor when I DID hear it. Sure, there are some installs, like where there are ground issues, or where the antenna itself requires a
certain length of coax as part of its design. But for the usual CB installation, FORGET about the coax length bull****, FORGET about velocity factor bull****, DONT WORRY about VF when setting up your station! IT IS ALL C R A P when it comes to the
USUAL CB mobile install that STARTED on CB, it LIVES in its ignorance on CB, it continues to THRIVE on CB, and will continue (apparently) to live ON CB ad infinitum. Not to make any comparisons, but I almost NEVER hear about "coax length" in any other radio media, or outlet---not even the hams spend so much time obcessing about the length of their coax!
And at the risk of length and making folks mad, I'm gonna to burst the coax length guru's bubble right now!:tongue:
As a ham, CBer and as user of certain other commercial and military frequencies (USAF and FEMA, etc) I run on my mobile what is known as a "screwdriver" antenna. It uses a 12V motor to move a 3" diameter coil UP and DOWN within a hollow mast (making it longer and shorter as needed) to operate HF frequencies between 3.5 and 30 MHZ. The antenna is resonant on EACH frequency of interest as it actually uses ONLY the number of turns that are OUT-side the top of the mast. By pressing a button on the dash, I can move this coil UP or DOWN to "tune to any of these frequencies.
NOW! Radio antenna theory is the VERY SAME for ANY band or frequency. CB radio is NOT "special" or requires some unique arrangement of coax length as if all other radio is exempt from the SAME rules. SO! IF what the CB coax length gurus say is true, and it MUST have 18 feet, or 9 feet, or some other ridiculous nonsense to work (to get them 'SWR'zzzzzzz' right), then to work 3.923 MHZ, I must have........OH
, about 60 FEET to work that 3 MHZ on that multi-band screwdriver! Then when I go to 7 MHZ, then I gots to have about 33 feet. Then at 14 MHZ, another at 16 feet, then another at about 14 feet. Then there's 21 MHZ at 11 feet, and then there's the 9 feet for 27-28 MHZ. IOW, according to the CB theory of coax length, I would have to have
AT LEAST 10 DIFFERENT COAXES IN MY LITTLE PICKUP so as to work all those various bands, and the screwdriver antenna could NOT work!!!! WHERE would I PUT all those coaxes in a small pickup truck?
Yet, I work ALL those bands from 3 to 30 MHZ (including CB, but actually I have a separate CB antenna for that to remain legal and use a legal CB set) with
ONE antenna, and
ONE coax of about 7 feet. The amp (when used--it's out of the truck right now: don't need it) has a jumper of about 10" long! The SWR is about 1.2 to 1 on ALL bands on that ONE coax and ONE "length" which is equal to that needed to REACH from the bumper to the radio!
Coax length and Velocity Factor used to tune antennas is bull**** and a lot of hocus pocus designed to make people think they know more than the other folks about radio. Coax length is that length that is directly proportional to the distance between the radio and the antenna. And THAT's the bottom line!!!!!!
If I upset somebody, I'm sorry; it's just the way I feel about it! NObody has ever been able to answer this with a true and accurate rebuttal because they CAN'T!:laugh:
CWM
