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

Re: Question regarding gain of Dish Antennas with different feeds



The gain will increase if there is better illumination of the dish. However
the feed will then pick up ground noise that reduces SNR. For receiving
don't go for more than -10 dB illumination at the edge of the dish. -15 dB
might be better if you have a low noise figure preamp.

73,

John
KD6OZH

----- Original Message -----
From: <W1BFN@aol.com>
To: <amsat-bb@AMSAT.Org>
Sent: Wednesday, 25 July 2001 16:44 UTC
Subject: [amsat-bb] Question regarding gain of Dish Antennas with different
feeds


> I looked at the G3RUH Patch Feed last night and must have one!
>
> Question: Will the Gain of the patch antenna increase the overall gain of
the
> dish I put it in, either directly by virtue of its stated gain, or
indirectly
> based upon better coverage of the dish surface? I understand that going
> circular will certainly help, and why.
>
> It's probably too soon to make an intelligent decision about this, but
given
> the S meter calibration of my receiver, I can copy SSB with difficulty
down
> to about 3 dB above the noise level, and reasonably well at 10 dB above
the
> noise. Given that I should hear no signal louder than 10 dB below the
beacon
> in an ideal, Leila controlled world,  then I think I must be able to hear
the
> MB at 13 to 20 dB above the noise. That level is approximately S7 to S9 on
my
> receiver. Even with fairly favorable  squint angles (below 15 degrees), I
can
> only maintain S7 out to 39,000 km, and that is where I can no longer use
the
> transponder. Going circular with a good same-size dish won't help very
much.
>
> This begs the question: How much addition gain Might we expect from the S1
> dish when it is brought on-line? as much as 10 dB? that would be good, I
> think, but would it be good enough? Inquiring minds want to know.
>
> Mike, W1BFN
>
> ----
> Via the amsat-bb mailing list at AMSAT.ORG courtesy of AMSAT-NA.
> To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org

----
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