[RFI] Ultrasonic Dish

[Don Nelson]

Hi all,

A parabolic dish to be used for ultrasonic purposes uses the same 
physics as a parabolic dish used in a flash light or in microwave 
applications. I dabble in the microwave arena. The engineering is the 
same. A dish has an f/D ratio that is the where f is the focal point 
dimension and D is the diameter. The feed beam width chosen to be used 
for a dish has to be matched to the f/D to get optimal performance. I 
suspect that the ultrasonic sensor has a wide beam width and so is best 
matched to a deep dish. A deep dish has a low f/D radio such as f/D = .3 
or so.

A few years ago I was driving through town and saw the traffic light 
people changing out the light bulbs for LED traffic lights. Yup those 
were deep dish parabolic units being scrapped and I got a bunch. They 
work well to 24 GHz. The point here is you may find a suitable parabolic 
dish in unusual places. Have fun looking!

Don, N0YE







On 1/1/2013 8:49 PM, rick darwicki wrote:
> I'm considering building the W1TRC arc detector from April 2006 QST.
> Any ideas on a cheap source for the parabolic dish?
> Worth the effort?
>   
>   
> Thanks
>
>
> Rick, N6PE
> ==================================
>   Talk is cheap... except when Congress does it.
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