I know, cut the top off of a 150W incandescent light bulb and use it
to make a radome.
-Chuck Harris
jimlux wrote:
Predrag Dukic wrote:
Bill,
Pyrex ( and any other glass) could reflect too much. It is true that
glass,
depending on composition, is not absorbing microwaves, and does not
heat itself in the owen,
but how much it is transparent at 2.4 ghz should be checked somehow...
P. Dukic
I wouldn't use a glass jar/mixing bowl, what-have-you.
A) glass is a bit lossy (even at 100-200kHz), but probably not enough to
be an issue.. (Now, if you were building kW scale capacitors for a tesla
coil, that's a different thing)
B) A bigger problem: Glass has a (unevenly controlled) dielectric
constant of around 2.5..
So, you'll get reflections at both interfaces as well as some refraction
as the signal passes through the "radome"
The whole radome design thing is much trickier than one might think for
a something where angle of incidence is important. There's a reason that
you see lots of hemispheres, and one tries to control the thickness of
the radome (in fact, sometimes, you make the shell from a honeycomb core
with 2 face sheets, although at L band, this would be tricky).
So, either you use something simple, and accept whatever defects it
creates in your antenna pattern, or get fancy.
Glass babyfood or canning jars will probably work, and will literally
last your life time. White painted plastic would also work.
Watch out for things like appropriately venting it (so moisture doesn't
collect inside) and making sure it doesn't make a little solar oven
(gotta paint that clear glass, I suspect)
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