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Re: RE:Re: AIDC Downconverter Survey Results



on 2/21/03 7:19 PM, Lee at lee-fl@cfl.rr.com wrote:

> 
>> 1.) There is a FIXED dynamic range to the satellite.  From the beacon to
> the
>> noise floor this is about 20 to 23 dB or so.
> 
> From the MB to the noise floor is 33 db per the articles published by the
> designers and measurements by several stations using various methods.
> 

I stand corrected.  Several other people talked about a 20 to 23 dB or so
range and I assumed they were correct.  With the extra 10 dB, then there is
quite a bit more difference.  And then there's a much larger possible range
of signals.  I know you were trying to verify the 33 dB number.  It would be
interesting to see what you find out as well.

> True that the S2 ALC is primarily impacted by the L-band stations that are
> mostly unrestrained by AGC.  But since LEILA can only get a certain number
> of offenders at a time, and worse largely ignores some formats like CW and
> SSTV, over powered U-band stations do have a great impact on the uplink
> receiver sensitivity by driving the U-rx AGC up.

Agreed.  Although someone questioned my statement that most of the "Loud"
stations were L-band.  While Leila doesn't catch things like SSTV and can
only catch 4 people at a time, she is quite aggressive.  It is not possible
to run an SSB signal as strong as the beacon while uplinking on U band for
very long.  You might get away with it for a few minutes, but not for all
that long.  But that said, if there enough U-band stations running excessive
power that Leila can't catch all at once, then the AGC WILL be negatively
affected as you say.  If one gets notched, yet another takes its place the
cumulative effect will still be the same.

The rest of your points, Lee are well taken.  It's certainly best to not
crank up the power when the AGC starts cranking up.  It's tempting, but not
good.


73,

Jon
NA9D

-------------------------------------
Jon Ogden
NA9D (ex: KE9NA)

Citizen of the People's Democratic Republik of Illinois

Life Member: ARRL, NRA
Member:  AMSAT, DXCC

http://www.qsl.net/na9d   <- Updated on 1/22/03!!!

"A life lived in fear is a life half lived."


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