Roy Lewallen wrote:
Mike Coslo wrote:


So is the lesson that Ladder line sucks, or is it that we
shouldn't wash our ladder line with soap and water? 8^)


Although I discovered it long ago, I keep getting surprised at how many
people require a binary answer to any question -- is it good or bad,
sucks or doesn't suck, good or evil. Sure makes it easy for our would-be
politicians and their 15 second sound bite solutions to complex issues.

Hi Roy. I must have used the incorrect wording here. I'm pretty well
convinced that PE coated ladder line doesn't suck. Just one of those
email things I guess... 8^)


Hopefully at least some readers will consider what Owen said, that the
knowledge we've gained by this can hopefully help in the intelligent use
of the line. Those needing a binary answer should look elsewhere; there
are plenty of gurus who are more than happy to categorically state
positive but simple answers to just about any question. I use a coin,
myself, but each to his own.

I ask the questions that I do to find out what might be going on. I've
learned a few things here. one is that if you coat PE with some
substances, it will alter it's properties.

Another is that there is a measurable difference in loss when a PE line
is coated with a wetting agent, which is needed to evenly (read wet)
coat PE with water. Some portion of this could be applicable to
non-wetted PE coated line.


Wes' and my measurements, and Danny's observations, can't be directly
applied to other situations. What they're meant to, and do, illustrate,
is that significant loss *can* occur under some circumstances, and
people who assume that twinlead or window line loss will always be low
can be very much mistaken.

However, some *are* applying them to other circumstances.


Has anyone run tests on what "real" (open) ladder line does when
you spray it with wetting agent and water?


I don't think any result would be very meaningful, except to show,
again, that significant loss could occur under some conditions (which
I'm confident is the case).

Agreed.

Those lines are often run with a very high
SWR. The effect of conductivity and/or loss across the insulators would
depend very heavily on the position and size of the standing waves. For
example, if the SWR is high and the insulators happen to be at or near
the voltage peaks, even a small amount of loss would have a major
impact. But on a slightly different frequency, the antenna's impedance
will change and the standing wave will move.

Good point

If most insulators are near
voltage minima, you wouldn't likely notice even quite a bit of loss.
This effect would be most pronounced at higher frequencies where the
spacing between insulators might become a sizable fraction of a
wavelength, and not so pronounced at lower frequencies or with more
insulators. But the magnitude of the SWR would still make a major
difference.

I would assume then that the big difference is the continuous coating of
the PE then?

Thanks for the feedback, Roy, I'm here more to learn than to argue.
(perhaps Quixotic?)

-73 de Mike KB3EIA -

Mike Coslo wrote:
Roy Lewallen wrote:

If most insulators are near voltage minima, you wouldn't likely
notice even quite a bit of loss. This effect would be most pronounced
at higher frequencies where the spacing between insulators might
become a sizable fraction of a wavelength, and not so pronounced at
lower frequencies or with more insulators. But the magnitude of the
SWR would still make a major difference.

I would assume then that the big difference is the continuous coating of
the PE then?
. . .

Classic ladder line and punched PE "window line" differ in several
fairly obvious ways, of course. First, the spacing of window line is
typically closer, so the leakage path is shorter. Second, the impedance
of window line is typically lower than window line, so the effect of
shunt Z on the impedance is less when the line is matched. But high SWR
could move the advantage either way, and for different load impedances
either type could have the higher SWR. Third, the fraction of the line
which is actually air-insulated is less with window line. Fourth, the
shape of the insulation is different -- flat with window line and
typically round for ladder line. This impacts the surface area involved
for potential leakage, and the way water might adhere. And finally, the
type of insulation is usually different -- PE for window line and
various materials for ladder line. (The coating of PE on the wires on
the sides of window line "windows" wouldn't make any significant
difference, except maybe to have some impact on how water would flow on
or off the insulating sections.)

Each of these will have some effect on the loss when wet, and different
effects as frequency and SWR change. As for the effect that I mentioned
where the loss could change quite dramatically with frequency or load
impedance depending on the position of the insulators relative to the
standing wave -- that won't happen at all if the insulation is solid,
and would be most pronounced when the insulators are distinct and
periodically spaced. So window line would fall somewhere in between.

Roy Lewallen, W7EL

Roy Lewallen wrote:
Mike Coslo wrote:

Classic ladder line and punched PE "window line" differ in several
fairly obvious ways, of course.


Thanks, Roy - good assessment there.

- 73 de Mike KB3EIA -