A thread that will never die

next you will have to have the right length of coax. i have shown the math involved already in my youtube videos, so please look there for explanations as to why coax length matters.
I will sell you the coax you need. (quote from another (closed) thread).

The "coax length" myth will never die until the last transmission is made by the last CBer on earth! I have often asked this question in an effort to dispel this myth. No one has ever been able to answer it because, truth is, coax length does not matter. THAT'S why its "coaxial" to start with, and why it is the antenna that is to be "tuned", not the coax. The coax is merely the means for getting the signal from the radio to the antenna, and it is 50 ohm (if the right kind) impedance anyway. Here's why coax length does not matter and I can prove it here with this simple bit of anecdotal evidence. IOW, the "proof" is in the pudding.

Many amateur radio HF operators operate from 1.8 MHZ to 29 MHZ-about 9 bands of frequencies that comprise our normal HF allocations. Some of us operate additional bands that also include certain military authorizations as well. In order to do that, we often utilize multi-band HF antennas that would also operate 27 MHZ if tuned to do so. One such antenna, very popular with amateurs is called a "screwdriver" antenna of which there a number of versions on the "web. This is a motorized antenna whose loading coil resides within copper or aluminum tubing. The motor moves the coil up/down as needed to tune to any frequency within that span of frequencies. Now, that being true, and because there are 8-9 bands of frequencies, the theory of the necessity of a "certain" length of coax encounters a problem! IF this theorem is true, and I *must* have 9 feet, 18 feet, 36 feet, etc. for the "SWR'zzzzzzzzzzzzzzzzzzz to be right, Houston, we have a problem! Being that antenna theory is the very SAME for 27 MHZ as it is for 3.8 MHZ, IF, according the the CB "technicians" I must have 9/18/36 feet of coax, or some such, then I must have 246/2 feet for 1.9 MHZ, 120/2 for 3.9, then 65/2 for 7.2 MHZ, 33.5/2 for 14 MHZ, 19.5/2 for 24 MHZ, and about 17/2 for 28 MHZ.

What I have done is used the generally accepted multiplier of 468/freq in mhz divided by 2. This references to a half-wave dipole and the "2" is the other half of the dipole. I have also skipped a few of these calculations for brevity. So if I *must* have a certain length of coax for 27 MHZ, then I must have the other lengths for each band to work. That, my friends, is based on the CB myth of 9/18/36 feet of coax for 11 Meters. So for 160 Meters, 80 Meters, 40 Meters, 20 Meters, 15 Meters, 12 Meters, and 10 Meters, I'm supposed to have 7-8-9-10 lengths of coax in my small pickup truck or else my "SWR'zzzzzzzz" are going to be bad! WHERE am I going to put all those lengths of coax in an S-10 pickup? Hmmmmm?

Yet. I, along with thousands of other radio operators, amateur, commercial, military, operate 80 thru 10 Meters with ONE coax with an average SWR (NOT "swr'zzzzzz") of 1.2 : 1 thru out ALL those bands, and talk regularly around the world. IOW, coax length is a myth that was born on CB, lives of CB, and will remain until CB is no more.

Can you "tune" coax? Yes and no. And the effect of such trimming is so small, it can hardly be measured.
And if you want to cut coax, do it! It won't hurt anything; won't help, either!

If you REALLY want to mess with the coax length guys, build an antenna and feed it with something called
LADDER LINE! !! It will blow their minds, LOL!