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Old January 19th 12, 08:59 AM posted to rec.radio.amateur.antenna
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Default Parabolic reflector

Jeff Liebermann wrote:

Note the C-Band DBS dishes may have holes in the mesh, but the mesh
itself is solid sheet metal.


Long ago and far away, I had one of those. It was not made of mesh, it was
made of a piece of sheet metal that had been perforated. The holes have to
be exact, besides the problems Jeff mentioned, they have to be small enough
and properly spaced that the dish still acts as a reflector at the frequencies
desired.

That's why Ku band (10gHz) dishes are usually solid. The mesh would have to be
very fine and precise.

The holes are not there to make it cheaper to produce the dishes, they are
to reduce weight and wind loading. I assume in colder climates they are
also there to reduce build up of rain water or snow.

Here in Jerusalem we have snow storms every 4-5 years. The last one was
enough that the snow caused our satellite dish to malfunction, which was
not welcomed by two kids stuck at home. Due to the rarity of the snowfalls,
the hilly terrain and the warm temperatures, schools just close for the
day of the storm and then reopen the next day after it has all melted.

Geoff.


--
Geoffrey S. Mendelson, N3OWJ/4X1GM
My high blood pressure medicine reduces my midichlorian count. :-(


 
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