On Sat, 25 Feb 2006 18:18:35 GMT, Big Endian
wrote:
"Ian White wrote
But the original questioner wants to measure what's *really*
happening.
========================================
But the original questioner can tell what's *really* happening just by
inspecting the antenna and feedline. He doesn't need any electrical
measuring instruments.

Actually I want to monitor the antenna because I have a splice in the
feedline and the feedpoint is subject to wx, snow ice and rain. Some
times the feedline itself is covered with snow and ice. I would find it
interesting to see what is happening when I see my SWR shoot up and
retuning my matchbox. I also have a strange thing happen when I apply
high power, I get a slight bump up in SWR suddenly. I often wonder if
one of my end insulators are breaking down under 1KW of RF or if there
is some imbalance on one leg due to ground or trees swaying in the wind.

Hi OM,

Reggie is particularly obtuse to this matter. Simple observation of a
dipole that is symmetrical to earth does not guarantee balance. When
that twin lead arrives at your gear, you can easily wipe that out (the
presumed balance) through an inappropriate connection to ground
(through any number of paths that are commonly overlooked in the
shack).

Snow and ice on the line are not likely to impart a common mode
current, but as revealed by bench test by contributors here, the
characteristic Z of the line can change drastically, which then upsets
the tune, where it follows SWR begins to change - noticeably. If your
feedline is coaxial, then the ice is of no consequence, but that does
not remove the jeopardy of common mode current. There you need to
look at how you isolate the line from the drivepoint.

73's
Richard Clark, KB7QHC