dish size/freq vs isolation formula

[updatelee]

I read the formula once to determine how many degree's of isolation a dish has but cant find it anymore, anyone know it ?

 

[jayelem]

Try this chart



How to calculate what size dish

 

[updatelee]

I saw a formula once, I think, lol. that would tell you the degree's of isolation on a dish based on freq and diameter.

for example if I wanted to make sure the when aimed at 89.0w I would not get any bleedover from 87.0w what would the minimum size dish I could use.

 

[Hermitman]

Is this what you're looking for?

BEW = L/DR X 57

BEW = Antenna Beamwidth In Degrees
F = Frequency In Hertz
L = 300000000/F
DR = Diameter Of Dish In Meters

Example: 3 meter dish, receiving 4 ghz (c-band)

Antenna Beamwidth = ((300000000/4000000000) / 3) X 57

Antenna Beamwidth = 1.425 degrees

Of course, this is with a perfectly shaped prime focus dish. Any imperfections can bring in unwanted signals. Have fun.

 

[updatelee]

exactly what I was looking for thanks !