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

Re: Prime Star Dishes etc.



Joe Leikhim wrote:
> 
> How does one determine the focal point of the Ptrimestar dish. I already
> know how to find phase center for the tri-band feed.

Hello,

Primestar dishes are offset fed.  The dish is a section of the parabolia.
The focal point is where the LNB is.  It also means that signals arrive
at an angle so the face of the dish will be 'pointing' lower than the
signal source.

The reason for the offset feed is it eliminates the shadow caused by the
LNB assembly.  Very common on small dishes (1 meter or less) where the
shadow is a higher percentage of the dish area.

73 Eric eac@shore.net  WB1HBU
----
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