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Re: PVC w/ H2O

Original poster: Gomez Addams <gomezaddams@xxxxxxxxx>

On Jan 15, 2007, at 6:53 PM, Tesla list wrote:

Original poster: Jim Lux <jimlux@xxxxxxxxxxxxx>

At 09:56 PM 1/14/2007, Tesla list wrote:
Original poster: Gomez Addams <gomezaddams@xxxxxxxxx>

On Jan 13, 2007, at 7:44 PM, Tesla list wrote:

Original poster: "Jim Mora" <jmora@xxxxxxxxxxx>


Somewhere in the archives is a loss table for different types of
coil forms.
I think maybe Richard Quick compiled them. I any case, PVC does
pretty lossey in the high freq spectrum.

Oh, absolutely!  I recently had to come up with a VERY low loss
radome for 5.3 GHz.  The only thing that was acceptable was thin
polyethylene.  Teflon would have been fine, but it's a bear to form,
and I had to have a closed-end cylinder.  I wound up using the bottom
of a 1 gallon vinegar jug!  Its presence was almost undetectable on
the network analyzer.

At work, we use Rohacell foam for this kind of thing.  I also had a
radome manufactured for a precision receiver (so we needed very low
and consistent loss) that was kevlar composite over a kevlar
honeycomb (I think).. the key was that the thickness of the
sandwich was designed to have low loss at our angle of incidence
(sort of like AR coatings on optical components).

We looked at that technique, but as it was for a satellite, angle of
incidence varied widely.  And after spending $4,000 on the antenna,
we couldn't afford a custom radome.  The next version / phase of the
project will use a custom-made, weatherproof, conformal/patch antenna
and I won't have to worry about a radome.

Okay, I'll stop being off-topic now.

 - Gomez

"Democracy is not something you believe in or a place to hang
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