For my own take on it I would say

1) You are in the near field of the antenna

2) The fact that the coax is, by own admission "bad"
would indicate there is sumpin' is up as old ratty coax
*can* actually appear to be good by giving a false SWR
indication.

I think this is where CBers get that old "18 feet of coax" thing so many
believe firmly. The thing to do is to use the
shortest run of coax you can, set the antenna by adding or
removing length and keep the thing out of the way of nearby objects (people,
cars, towers, fuel tanks. If you
re-resonate the antenna and re-attach the shorter line, it shouldn't make
any difference.


Jerry
K4KWH
"Keven Matthews" wrote in message
...
I recently moved my shack from an upstairs room to downstairs, much
closer
to the garden and antennas. All the antennas previously had a long run of
coax to the old shack. The obvious thing was to have a nice new short
run
of coax to my HF vertical which is now only 15' away. So I cut the coax
and
since then the antenna is no longer resonant on 40 Metres. Also this week
I
was putting up a new HF wire antenna, it was getting dark and raining by
the
time I was hoisting it up but so I could just have a listen that night a
grabbed an old (15 years) large coiled up of quantity RG213 coax
complete
with rotten oxydized pl259 plugs on each end which had just sat on the
garage wall for years. I just slung the coil down and plugged in at each
end. The plugs looked so rotten it was shameful but it pitch dark by
then!
However 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. Please could some
one
explain to me if the coax length does matter, it has certainly never been
a
problem for me in the past on VHF and Six but I am new to HF frequencies.
If you do need to have a certain size run, what can you do with the cable
if
you phisically dont need it ?


Many Thanks & 73 for 2004

Keven G7UUD