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# Re: Using C band polar mounts w/ ao-40

• Subject: Re: [amsat-bb] Using C band polar mounts w/ ao-40
• From: "Edward R. Cole" <al7eb@xxxxxxxxxxxxx>
• Date: Mon, 23 Apr 2001 14:11:37 -0800

```>From: "Vince R." <vincesr@ij.net>
>What is the theoretical gain of my "six" foot mesh TVRO dish at 2.4Ghz?
>Beamwidth? Links to equations/tables/shareware dish calculators
>will be welcomed!
>
>Vince Risalvato
>KD7AI

Vince,

The formula for dish gain is:

G = 10 Log [e*12.56*(diameter)^2/(wavelenth)^2]  in dBi

e = is the efficiency and ranges from 0 to 1 [for zero to 100%]  I set e = 0.5
Diameter and wavelength should be in the same units [feet, or inches, or
meters,...]

Your dish at 2400 MHz:
wavelength = 300/2400 = 12.5 cm
diameter = 6*12*2.54 = 183 cm
diameter/wavelength = 14.64, and squared = 214.3
solving the expression inside the bracket = 1356
in dB that is 31.3 dBi

Beamwidth = 57.3 Wavelenth/Diameter = 3.9 degrees

This is included in an Excel spreadsheet called g-t.xls found at:
http://www.seatileague.org/software/spreadsh.htm

Ed

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