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*Subject*: Re: [amsat-bb] Dish Formulas ?*From*: Michael Kjorling <michael@xxxxxxxxxxxx>*Date*: Fri, 29 Aug 2003 00:22:51 +0200 (CDT)*In-Reply-To*: <00b801c36dac$b9ee4ab0$6401a8c0@marketlab>

-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 On Aug 28 2003 14:38 -0700, Jim Tudehope (Peoria Arizona) wrote: > Does someone out there have a program already written to calculate dish > antenna parameters with just a few input variables ? I found the following formula for dish gain and -3 dB beamwidth. I don't know how accurate it is (it might be valid only for circular and near-circular parabolic reflectors), but the result matches that in a textbook I have that deals in part with satellite link budget calculations. $gain = (20 * (log10 ($dia / $wave))) + ((10 * (log10 $illum)) + 9.938); $theta = 70 / (($dia / 30.48) * $freq); The variables are as follows: $gain is the dish gain in dBi $theta is the -3 dB beamwidth in degrees $dia is the reflector diameter in cm $freq is the frequency in GHz $wave is the wave length in cm $illum is the illumination factor (typically 0.6?) 'log10 x' is simply the base-10 logarithm of x, such that 10^{log10 x} = x. Hope this helps. I realize that not everyone is a programmer, but if you just take out the $ signs (indicating variables) in the equations above and the semicolons at the end of the lines, it's pretty standard algebra. Michael Kjörling - -- Michael Kjörling :: michael@kjorling.com :: SMØYBY JO89 ^..^ PGP: 3723 9372 c245 d6a8 18a6 36ac 758f 8749 bde9 ada6 \/ -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.2.1 (GNU/Linux) Comment: Made with pgp4pine 1.76 iD8DBQE/ToC+dY+HSb3praYRAoIgAJ4zogYx6S6jy9RNGoMu9zw0afv4+wCfWiH1 kcK2NC2MxW8gIeIYjza4awc= =9nNr -----END PGP SIGNATURE----- ---- Sent via amsat-bb@amsat.org. Opinions expressed are those of the author. Not an AMSAT member? Join now to support the amateur satellite program! To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org

**References**:**Dish Formulas ?***From:*Jim Tudehope \(Peoria Arizona\)

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