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Re: DISH BEAM WIDTH



Bill:

G(dB) = 10Log [4*pi*e*diam^2/WL^2]
pi = 3.1459
diam = 12/3.28 meters
WL = 300/2400 meters
e = 0.55  {55% dish effficiency}

f = diam^2/16*d
d = dish depth

HPBW = 57.3*WL/Diam

For your 12-foot dish:
d = 22 in
G = 37.4 dBi
HPBW = 2.04 degrees
f = 40.9 in
f/d = 0.34

Ed - AL7EB

At 12:24 AM 3/1/2003 -0500, walnuthil@juno.com wrote:
>Hello All,
>I recently acquired a TVRO 12 foot dish, with the mesh
>reflector. I have been trying to calculate the 3db beam width
>in degrees, the books I have are not clear on the formula.
>Does anyone have the correct math formula ?
>Putting a 2 by across the dish and measuring down the
>center is 22 inches. Yields a f/D = 4.0 if the formula is right.
>I plan on using it for receive on AO-40, I have some tall pine
>trees to the south that reduce the down link signal. 
>Hopefully this dish will help.
>Thanks in advance
>Bill

>WA1DMV@amsat.org
>#20942
> 
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