On Sat, 23 Sep 2006 18:25:55 -0400, Mike Coslo
wrote:


I don't know that it is fair to say that "Ladder line sucks", but it
is well known that it is adversely affected by moisture. Ladder line
is not so good wet or dry as to disregard its losses in all situations
(ie in general).

I wonder what the exact mechanism is? PE has some decent water
absorption characteristics, 24 hour tests show almost no absorption for
low density, and none for the high density and up versions.

I don't recall seeing suggestion that the mechanism is a change to the
PE due to absorption of water.

The water on the surface of the PE is immersed in the E and H fields,
and is likely to change the RLGC characteristics at a frequency.

I think Wes' work was valuable in demonstrating that the changes are
not lossless, even if it is not practical to estimate the magnitude of
the changes because of uncertainty in the "wet environment" at any
point in time.

So, we know that the changes in loading that we observe with an ATU
are likely to have an increased line loss due to the water. That loss
warrants consideration, a reason to consider other line constructions
in certain environments.

Wes and I discussed inclusion of his "wet" figures in my line loss
calculator at http://www.vk1od.net/tl/tllc.php . Wes' preference was
to not include them, I am happy with that in that you could read too
much into the calculated results because of the lack of standardised
"wetness" in the real world.

Owen
--