Hi John,
When I figured the focal point in my parabolic dish, I used
the following formula, that I got off the internet by doing a google
search. I'm going to use inches, since I don't have anything handy to
measure mm .....
18" diameter squared =3D( 324" ) / 16 x 5" depth =3D( 80")
making the focal point 4.05 inches out from center. I used 16 as the
multiplier for the dish depth, instead of 4.
So if I've figured this wrong, than I need rod couplings to add another
10" on to my 6" rods that support the rubber band suspended stereo mics
to get closer to the correct focal point. These mics don't seem to
produce any stereo sound , as the separation between them is only 2.5"
with no divider in the dish. A decent mono sound, but I'm thinking that
they also need more wind protection than the tiny foam windscreens.
Regards,
Bill
In "John Tudor" <> wrote:
>
> Measure the diametre of the dish.
> Lay a ruler across the dish and measure the depth in the centre
>
> The formula for finding the focus of a Parabloa is as follows
>
> (Dia Squared)/(4 x Depth)
>
> Example. Dish is 1200mm in dia (1200 Squared is 1,440,000)
>
> Depth is 600 mm deep at the centre (4 X 600 =3D 2,400)
>
> 1,440,000 / 2400 =3D 600
>
> So the focus is 600 mm out from the centre
>
> Fine tune it from there
>
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