Owen Duffy wrote:
"826" wrote in
:

Hi. Have a new Hustler 6 band vertical. Installed the radials and also
buried 75 foot of RG213 coax between shack and antenna. I used a 6
foot peace of coax connected to adjust the antenna with a MFJ-259.
Every band was tuned to the middle and SWR was lower than 1.7:1 at the
edges. After the adjustments, I reconnected the buried coax to the
antenna and on all bands everything had shift up by any where from 200
to 400 khz. Now the rig is seeing greater than 2:1 SWR.
Should I retune the antenna with the MFJ 259 in the shack?

Vern,

An oft asked question, and there are usually emphatic answers readily
proffered.

You might find my article at http://www.vk1od.net/VSWR/displacement.htm
relevant to understanding what goes on 'within' the transmission line,
and the 'Traps for players' heading offers reasons why behaviour that is
inconsistent with transmission line behaviour may be observed.

In your case, one of the things you appear to have done is the change the
thing that was measured. You adjusted the antenna with the shield of the
main feedline disconnected. This is discussed under the heading
'Disturbing the thing being measured'.

Owen

But, if the choke/balun/unun suggested is implemented, shouldn't one
expect the transmission lines influence to measurements be expected to
drop to near zero effect/affect?--i.e., re-routing/lengthening/etc. that
xmission line (coax), opposed to measurements taken?

Or, in effect, your measurement(s) with a 1 ft. length of xmission line
will remain very stable if that length were lengthened to one-hundred
feet?; Given that the choke/balun is of proper construction to offer
HIGH impedance to the freq(s) in question on the outer braid/shield?

I certain have grown to expect this ... have I just been lucky?

Regards,
JS