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

Re: Once again: Realistic BBQ Dish Gain with OriginalDipole Feed, an



I've been looking at the AGC data since the transponder has been off and yes
there is some activity but rarely  and not what I'd call high.

To put some measured perspective into the discussion, looking at a five
orbit period after the transponder was turned off, the U-Rx AGC is at its
quiet baseline value (-1.3) 80% of the time.  90% of the time the AGC is
below 6db and the remaining 10% finds the AGC within a 6-9 dB range.  By
comparison, during the prior five orbits that the transponder was on, the
AGC was above 6 dB for over 25% of the orbit and spends almost 16% of its
time above 10 dB.

I've updated my web page to include a total of 15 orbits of charts and also
recently started adding some plots of the footprints to show which areas are
in view during those periods with the most noticeable AGC activity.

http://home.cfl.rr.com/lmclamb/ao40agcanom.html

If you compare the various orbits it is clear that the vast majority of AGC
activity is due to operators running excessive power.  Also of interest is
that a lot of the activity since the transponder was turned of is when the
North and South American Continents are not in view.

There are probably several factors which lead stations to run excessive
uplink power and not everyone with a weak receive configuration is guilty.
However, if a station has barely a 10 dB SNR and "something" drives the AGC
up causing their receive to drop 6db they will be much more inclined to
increase the uplink power than the station which started off with an 18 dB
SNR and still has solid copy even with the higher AGC.

73,
Lee-KU4OS

----- Original Message ----- 
From: "Jon Ogden" <na9d-2@speakeasy.net>
To: "Bill Booth" <710138@ican.net>; "amsat BB" <amsat-bb@AMSAT.Org>
Sent: Thursday, May 08, 2003 7:31 AM
Subject: Re: [amsat-bb] Once again: Realistic BBQ Dish Gain with
OriginalDipole Feed, an


[snip]
> They look at the AGC numbers and are convinced the high readings are due
to
> the guys who can't hear as well.  Yet even with the transponders turned
off,
> those AGC numbers are still high sometimes!  It's more likely some other
> sort of received signal is doing it that isn't amateur at all!
>
> 73,
>
> Jon
> NA9D

----
Sent via amsat-bb@amsat.org. Opinions expressed are those of the author.
Not an AMSAT member? Join now to support the amateur satellite program!
To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org



AMSAT Top AMSAT Home