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Re: L band Uplink



Let me add my observations from a recent test of my L-band uplink (L1) when
AO-40 had 38 degrees of elevation at my QTH (San Jose, CA), was at a range
of just over 36K miles and the computed squint was 12 degrees.  35W (CW
mode) into an 18.4dBd antenna (M2 23CM35EZ) with a 1.6:1 SWR  gave me a
downlink signal that was just over 8dB below the middle beacon as measured
on my spectrum analyzer.  The same setup on L2 produced a downlink signal
that was 14dB below the beacon.  The computed EIRP for this setup is
approximately 4.3KW and I believe that this portion of the AO-40 pass is
fairly typical of operating conditions, so this doesn't seem to be a QRP
bird on L-band.

73,

Rick
KG6IAL

----- Original Message -----
From: "John Mock" <kd6pag@qsl.net>
To: <amsat-bb@AMSAT.Org>
Sent: Wednesday, June 12, 2002 10:05 AM
Subject: Re: [amsat-bb] L band Uplink


> I looked into this myself before even running antenna simulations, and
> attached is a collection of messages from earlier this year on the topic.
> I wanted to try to calculate this myself, but i can't run the Excel
> spreadsheets on PowerPC LINUX and couldn't find anything about how to
> calculate these things manually.  Collected estimates of needed EIRP
> varied from 400W to 8KW, depend on various factors, especially squint
> angle.
>
> So i picked the 1KW SSB figure and tried to get 20dBi gain on the uplink,
> in order to run QRP.  I may be falling somewhat short of that, due to
> linear vs. circular polarization mismatch.  But so far, i'm not hearing
> myself at all on the downlink, but the squint angle wasn't great, i'm not
> sure how much power i'm using or factors like SWR (both to be determined
on
> Friday), and i'm not certain that the homebrew antenna design is working
> properly.  I can comfortably copy anyone vaguely likely to interest LEILA
> on the 2.4G side of the dual-band feed, without any noticable de-sense
from
> the 1.2G side to the beacon or SSB QSO's.  I think i'm under-illuminating
> my dish, so there may be room for some improvement.  I'm not 100% certain
> about the frequency calculations, either (other than avoiding the MB).
>
> I'll report back later this week. Meanwhile, anyone else have any clues?
>
>          -- KD6PAG


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