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RE: Alternatives to fiberglass boom



Thanks to G4DMF, I8TDJ and G3WDG for their thoughtful comments criticizing
my suggestion on the use of a microwave oven to test the dielectric
properties of materials:

> As a domestic electronics engineer, I am somewhat alarmed at
> this reply. If the material is good at 2Ghz, then you are
> running your 1Kw microwave transmitter ( your microwave oven
> ) into a VERY high SWR, certainly running it for 1 minute
> could irreparably damage the magnetron. It is VITAL that any
> tests of this type are conducted with at least a beaker
> containing 250ml or so of water accompanying the piece of
> dielectric to be tested.

I don't disagree, but I note that the trick I suggested (without worrying
about the glass of water) has been used for a number of years in
professional microwave labs. Perhaps the magnetrons intended for residential
use simply don't have this susceptibility, because I have never had one
fail.

As a confession, I have had items "flame" when under test, which was the
reason for my "try a few seconds first" suggestion. A good example of a
spectacular flame was generated by "Miking" a CD to render it unreadable
(the CD equivalent of a paper shredder). The first few seconds produces
spectacular fireworks as the metallized innards flash over. Then the plastic
can flame and create a horrible smelly mess. This nearly caused a divorce in
the Clark household ;<}

73 de Tom, W3IWI


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