My advice would be to experiment with cheap sources of reflectors. The
original parabolic reflectors used by natural history recordists were
radar dishes which could be bought cheaply after the War in the
late 1940's and 50's but these were quite heavy. I agree that spun
aluminium dishes would be a bit resonant if they weren't backed by a
stiff layer, but then they wouldn't be lightweight.
The theory suggests that the dish profile is not critical as the
shorter wanted wavelengths are around 2.5cm (1 inch) - so small
irregularities wouldn't harm. Even the differences between a parabola
and a spherical dish are small.
Has anyone tried using discarded satellite dishes? There must be some
around, but even new ones are not expensive. They are shallower than
conventional mic dishes, but should still give a good focus and they
have a focus mount already fitted.
My Brinibox prototype gives a 12 dB gain and the stereo sound is good
for the money, and it is made out of cardboard. How about a cardboard
prototype parabolic mic?
David
David Brinicombe
North Devon, UK
Cogito cogito ergo cogito sum - Ambrose Bierce
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