| Subject: | Re: Parabolas and low frequencies |
|---|---|
| From: | "John Crockett" naturalcontemplative |
| Date: | Mon Feb 13, 2012 8:18 am ((PST)) |
Hi David, I'm not sure what you mean by "extinction point." My dish has a 4" (102mm) = focal length. Does that mean the lowest frequency it can resolve is 406.4mm= , or about 838 Hz, no matter how big the dish diameter? My confusion is obvious, I'm sure! Thank you for your help! John --- In "Avocet" <> wrote: > The "extinction point" is theoretically where twice the focal length > is half the wavelength. At 334 Hz the wavelength is 1 metre, and the > "extinction" focal length 250 mm or about 10". Note the word > "theoretically". > > > David > > David Brinicombe > North Devon, UK > Cogito cogito ergo cogito sum - Ambrose Bierce > |
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