Re: Leaky Coax

On Tue, 14 Feb 2006, in the Usenet newsgroup alt.internet.wireless, in article
<pda2v1tegrpr7rv0eoji516c6ui5qdivo0@xxxxxxx>, Jeff Liebermann wrote:

(Moe Trin) wrote:

$3 to $16 used on Amazon.

Geez that thing has gotten expensive. That's a text book that been out
for quite a number of years. My copy looks to be from 1976, bought for
US$ 16 for a class at HP taught by the author.

My copy walked away at a consulting job about 10 years ago. I miss
it. I think I paid about $50 in about 1980.

There've been at least five printings of it - probably a lot more. My
copy is a 4th printing, and has a LoCUS catalog number of 76-82902 and
what I take to be an ISBN number of 13-581488-X, though it's copyright
date is 1969.

The above explanation is a simplification, for conceptional use.

Simple to anyone with a few years of network analysis.

As you know, it's very hard to provide a decent background/explanation
on Usenet. That post was what, a hundred lines? The class that Adam
taught was two semesters two nights a week. I got conned into it by
the company requirements of "continuing education", and the class (from
Foothill-DeAnza) was held at 1500 Page Mill Road, in his lab area.
And of course, he's got all kinds of nifty toys laying about - some
of which probably retailed for something like my annual salary at the
time. But he's a good teacher and knew what he was talking about, and
had the gear to be able to demonstrate an answer to a question. Quite
formidable. I don't know about the rest of the students, but _I_
certainly got a lot out of the class.

Worse. The leaky coax is a distributed attenuator with a combination
of leakage and dielectric attenuation. The leakage (radiation) is
fairly uniform along the length but tends to leak more at the source
end due to dielectric attenuation effects. Modeling doesn't look too
horrible.

Fun case one time - I'm visiting a site that is unstable, and no one
knows why. It's a C-Band rig with multiple antennas, ferrite switches,
and automated RF monitoring up the whazoo. Finally I notice that if I
open the cabinet door while monitoring the reported VSWR, I see that
the angle the door is open has a huge effect. WTF??? Finally spot
the fact that one of the waveguides way down in the back of the cabinet
is wrapped in masking tape over what appears to be aluminum foil...
Some unknown _factory_ tech had damaged the flexible (corrugated)
guide - and "repaired" it by tightly wrapping the tear with foil, and
holding that in place with masking tape.

PREDICTION OF INDOOR WIRELESS COVERAGE BY LEAKY
COAXIAL CABLE USING RAY TRACING

A Leaky Feeder Model for Indoors Impulse Response Modelling

Ghod, I'd need a drink after that. ;-)

Old guy
.