[Date Prev][Date Next][Thread Prev][Thread Next] - [Date Index][Thread Index][Author Index]

Re: AO-40 spreadsheet



Remember this:  Gain is basically proportional to the dish area.
If you lose 3dB by using linear instead of circular polarization,
you have to DOUBLE the area of the dish to compensate.
A bigger dish is heavier, more expensive, has more windload,
and has a narrower beamwidth, so you have to point it more carefully.

Also, using a carefully designed offset feed would get
you a couple more dB of SNR compared to a quick-and-dirty 
non-offset feed.  These are "free" dB, since they do
not increase the size of the antenna or its beamwidth.

Maybe some commercial enterprise will start selling
a carefully-designed and optimized dish/feed assembly...

Doug
NA1DB

At 04:11 PM 5/25/01 , you wrote:
>Wow, this spreadsheet is truly enlightening.  There's nothing better
>than a good model to quickly teach how things work.
>
>I notice that the ability to hear the transponder is VERY dependent on
>the antenna gain, and relatively independent on the gain of the preamp.
>For example, there appears to be no benefit to having a preamp gain of
>more than 10-15 db.  Same for the Converter.  Don't waste your money on
>super high gain components, just get a really good antenna.
>
>So, my question:  Given the high dependence on antenna gain, besides
>renting Arecibo for the weekend, what will give the most gain for the
>buck?  I'm starting with an 18"x36" grill antenna with a dipole+hat feed.

----
Via the amsat-bb mailing list at AMSAT.ORG courtesy of AMSAT-NA.
To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org



AMSAT Top AMSAT Home