highway man,
i used bad terminology. i should have said impedance transformer.
here is some more in depth stuff if anyone is interested:
https://en.wikipedia.org/wiki/Quarter-wave_impedance_transformer
the people who are saying that coax length doesn't matter are correct.
that's the whole point of the invention of coaxial cable in the first place.
it's entire reason for existing is to provide a path from your radio to your antenna without becoming part of the antenna.
however, because of the distributed constants on the line, there is always the chance that your particular length of coax used at a particular frequency ends up becoming an impedance transformer and would show you a different SWR at the antenna end of the coax than it would at the radio end of the coax.
so, for CB radio at 27 mhz, with a length of coax that has a .83 vf, staying away from the lengths i posted by a foot or two in either direction is sort of an extra piece of insurance against accidentally hitting one of those 'magic' lengths.
so just run whatever lengths of coax you have, unless you happened to buy one with just the wrong length as shown in my last post.
also remember that when your amp is on, and you put an SWR meter in between your radio and the input of your amplifier, that you are reading the match between your radio and the input tuning circuit inside the amp, not the SWR of your antenna system.
with the amp on, you need to have an SWR meter AFTER the amp in order to read the SWR from the output tuning circuits of the amp to the antenna.
some amps are better tuned than others.
this is one reason that people have so much trouble when they install amps in their vehicles and they blame it on the antenna.
here is more info on this stuff than anyone wants:
http://www.rfcec.com/RFCEC/Section-...al Cable VSWR 3 (By Larry E. Gugle K4RFE).pdf
LC