[TowerTalk] NOT ALL PLASTICS ARE GOOD INSULATORS - TALE OFABEVERAGE PROBLEM

[Perry - K4PWO]

Easy way to gage the relative suitability of a plastic for RF is the 
microwave test.
Place a microwave safe container with one cup of water in the microwave and 
place your test item in the microwave.  Start heating in 10-15 second bursts 
checking the test piece between bursts.  It the test item warms or gets hot 
you have a material that is suspect for RF (it might still work at HF).  If 
after a total of one minute the test piece is still at ambient you can use 
it with a fair degree of confidence.

73 de Perry - K4PWO

----- Original Message ----- 
From: "Peter Voelpel" <df3kv at t-online.de>
To: <towertalk at contesting.com>
Sent: Friday, December 12, 2008 11:59 AM
Subject: Re: [TowerTalk] NOT ALL PLASTICS ARE GOOD INSULATORS - TALE 
OFABEVERAGE PROBLEM




-----Original Message-----
From: towertalk-bounces at contesting.com
[mailto:towertalk-bounces at contesting.com] On Behalf Of Larry Schimelpfenig

The moral of the story is "use red boxes instead of black to house matching
and reflection transformers for beverage antennas";-).

While the odds of a plastic box being conductive are fairly small, our
expereince shows that it can obviously happen. It's entirely possible that
the pigment used to color plastic could be a conductive material such as
carbon!

73 de Larry K7SV




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I can only agree on that!

FOR WAE SSB 2005 at DF0CG/DR1A I installed two 80m halfsquares at 90° two
each other with a matching network and direction switch.
A coil, vacuum variable and vacuum relay went into a large black plastic
box.

Look what has been left next morning:

http://www.df0cg.de/pictures/gallery/contest/waedc_ssb_2004/PICT0852.jpg

http://www.df0cg.de/pictures/gallery/contest/waedc_ssb_2004/PICT0844.jpg

http://www.df0cg.de/pictures/gallery/contest/waedc_ssb_2004/PICT0845.jpg

73
Peter

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