18 feet of coax is NOT needed

That would be WAY overkill! Surely a waste for a single frequency using a multi-band and a "wander lead" ! I have several 10-11 Meter antennas a whole lot cheaper.

But talking about coax length, I was trying to illustrate that coax "theory" is the same for any band/frequency. SO if the CB "gospel" of 18 foot coax was true, then it would be true for 75 Meters, too. So that would mean I would have to have 60 feet of coax in my car to operate that frequency. But, yet, I work EVERY frequency from 3,5 MHZ to 28 MHZ with ONE coax and ONE antenna with an SWR of 1.2 : 1. And that coax is (get ready)....................
less than 7 feet! Not even a "multiple" of anything! Doesn't relate to anything.

Coax has little to do with it, It is the ANTENNA that transmits the signal, not the coax! Tune the antenna, NOT the coax, and MATCH the antenna at the feedpoint, not by trimming coax!

 

The dipole formula is good enough for a mobile antenna. The proof of what works is in the pudding! I've worked the world several times over using the 468/frequency in MHZ to get a ball park figure and tune a mobile antenna to frequency. The advent of the screwdriver antenna has made that less necessary. For the dipole, it will NEVER exact because of surroundings, ground integrity, soil content, mineral content, moisture. So when you put up a dipole, I always cut it a smidge too long. That way I can cut it to length, let it "stretch" (cure) for awhile, then trim if necessary. Likewise, the mobile antenna gets us a "ballpark figure", and I was also disputing the "coax length" theory using the 468 because the coax trimming crowd believes in "length" which actually has little effect in the real world. It was the simplest way to explain it to those who, perhaps, aren't involved in the mechanics of radio, and rely on the back lot CB shop with their "snip and clip" stuff.

 

18 feet works fine.

Peak and tune
18 feet of coax
Good antanae and mount
Noise canceling mic
Good cb.
Dipole and pages of algebra is for the insane.

 

Its easiest for me to use 18'ft. In a crapcadia....In certain other trucks 9 ft. Would work just fine.

 

I will always use 18 feet because that's what they say, plus I can afford it

 

I think the reason that myth gets perpetuated is because you will almost never See x=0 when r=50 unless the cable is used to transform the impedance. If you ask the average truck driver if they know what a shunt matching coil is they will have no clue what you are talking about. Telling people the antenna needs to be matched at the feed point doesn't explain to them how to accomplish that objective-it simply confuses them. Telling them HOW to match the impedance at the feed point would probably be more helpful.

 

Still will always say it's the quality of the Coax. LMR240-LMR400 OR RG213 COSTS MORE $$$ BUT IT GETS THE JOB DONE. ######## CONNECTERS WILL GET YOU NOWHERE WITH ANY OF THOSE COAX.

 

I get my 18 feet from a cb shop.
Always works good

 

Some cb shops and techs look at feed point and where that exactly is differently

 

If in it ain't broke then don't fix it.