[RFI] Ultrasonic Dish - CORRECTION

[N1BUG]

On 01/02/2013 07:59 AM, N1BUG wrote:
> The type with one 50 to 60 degree lobe approaches ideal use of the
> dish **if** you use a flat enough dish. You want a dish with f/D in
> 0.7 to 0.75 range for these.

But I was wrong! I should have reviewed my notes before posting 
that. The commonly available transducers have a 10 dB beamwidth of 
~65 degrees. 10 dB down at the edges of a dish is considered optimum 
for gain in RF work. I'm assuming that applies equally well to 
ultrasound. This results in f/D of 0.82 for maximum gain.

73,
Paul N1BUG