Re: [amsat-bb] Sun noise

["Lee" <lee-fl@xxxxxxxxxx>]

----- Original Message -----
From: "Tom Clark, W3IWI" <w3iwi@toad.net>
To: "'Eric Van Offelen'" <eric@vanoffelen.com>; "'Amsat-bb'"
<amsat-bb@AMSAT.Org>
Sent: Saturday, December 21, 2002 14:15 PM
Subject: RE: [amsat-bb] Sun noise


[snip]
>
> The radio sun at 13 cm, depending on sunspot count, is about 40,000 Kelvin
> and is about 1 degree in diameter. Therefore the sun fills about (1/10)^2
or
> ~1% of the beam. Therefore, the sun should contribute about (1/100)*40000
=
> 400 degrees Kelvin if you dish has perfect (100%) aperture efficiency.

Tom,

I was under the impression that the antenna beam width correction was to
compensate for very narrow beam widths in which some of the sun's energy
falls outside the view of the dish. The formula I've been using is from the
SETILegue and seems to match my measurements on both the 60cm and 90cm dish.
Their web site  which is what I've been using for my g/t measurements is
http://www.setileague.org/articles/g-t.htm

Are they wrong or did I misinterpret something?

Take Care,
Lee-KU4OS


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