Kevin, the resonance of the antenna is determined by the length of the
antenna! It is not related to the VSWR!!!

If you are using VSWR as an indicator of resonance it is meaningless!

Since your VSWR is changing with length of Coax, I suspect you have RF
on the braid of the coax. Install a series of Chokes or ferrites.

W1MCE

Keven Matthews wrote:
SNIP
The SWR was pretty good across the band. Regardless I started my
evening doing a tidy job with some of that nice 5DFB japanese coax all ready
for the following day. Guess what ? I put on the nice new cable and plugs
and the antenna is no longer anywhere near resonant on 80M. So why am I
getting a better result with a long length of still coiled cable sitting on
my patio rather that a much shorter brand new piece.

SNIP