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Re: AO40 downlink signal strength



The 1999 ARRL Handbook indicates that AO-40 users should shoot for a
gain/temperature (G/T) ratio of 0.53 for the S-band downlink. This most
likely assumes an off-pointing angle of 0 and more gain would be required
for greater off-pointing angles. For various system noise figures this works
out to the following antenna gains:

NF (dB)   T (K)   Gain   Gain (dBic)   Antenna Type
-------   -----   ----   -----------   -------------
   3       290    154       22         30" dish
   2       168     89       20         24" dish
   1        75     40       16         16 turn helix
   0.5      35     19       13          8 turn helix

73,

John
KD6OZH

----- Original Message -----
From: "Ed Krome" <71611.76@compuserve.com>
To: <nx7u@arrl.net>
Cc: "Ed Krome" <71611.76@compuserve.com>; <amsat-bb@AMSAT.Org>
Sent: Tuesday, 08 May 2001 02:48 UTC
Subject: Re: [amsat-bb] AO40 downlink signal strength


> Message text written by INTERNET:nx7u@arrl.net
> >
> Is this an accurate synopsis of the situation?  Is it possible that
> "easy to get on mode-S downlink" is that suboptimum?
>
> I'm not trying to ruffle feathers here, but these thoughts are what so
> far have paralyzed my efforts to get mode S going.  <
> -------
>
> Don't be paralyzed! My little survey of first day AO40 users yielded a
> surprising number of unmodified Drakes (~3+ db NF) parked behind barbeque
> grill dishes that did just fine. Yes, the UEK3000SAT is a tiger and there
> were a few behind tiny 16 turn helix's. But there were a LOT of Drakes,
> Transystems, DEMI's, homebrews, oddballs, what have you.
> As the commercial says "just do it".
>
> Ed K9EK
>
> ----
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