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R: Something OLD, Something NEW



Hi   Hasan,

You are right  because if you can hear several dB of consistent transponder
noise at apogee,any increase in antenna gain or  any decrease in noise
system temperature,ie reduction of receiver NF,will produce the same
amplification  both of the transponder noise and  transponder signal
leaving the receiver S/N unchanged.

Until i cannot hear the transponder noise,the factor limiting the
sensitivity of my system is the noise generated in to my receiver.
As soon i can hear the transponder noise at list with 3dB of (S+N)/N
corrisponding to 0 dB of S/N,the factor  limiting  my receiver sensitivity
  begin to be the transponder noise trasmitted by the satellite.

The noise trasmitted by the satellite transponder is not only the noise
generated  in to the transponder active components itselph but mostly by the
noise picked up by the satellite antennas oriented to the earth.

The satellite antenna pick up noise at  ground temperature of 290 kelvin
adding to it all  man made noise generated in to the 70 cm and 23 cm bands
as seen simultaneoulsly  on the ground by the AO40  70 cm ,and 23 cm
antennas

This is why the man made noise was the factor limiting the sensitivity for
the Mode-L transponder on OSCAR-13

73 de i8CVS Domenico




----- Original Message -----
From: hasan schiers <schiers@netins.net>
To: <amsat-bb@AMSAT.Org>
Sent: Friday, May 18, 2001 5:30 PM
Subject: [amsat-bb] Something OLD, Something NEW


> When you can clearly hear the "passband" noise of the satellite itself, no
> further improvement will help. Until you can hear it clearly....your
system
> is not as good as it can get.
>
>
>
> Once you can hear several dB of consistent passband noise at apogee, you
> will know that there is nothing you can do to make things better...you've
> reached the PINNACLE of receive performance.
>
>
> 73,
>
> ...hasan
>
> ----
> Via the amsat-bb mailing list at AMSAT.ORG courtesy of AMSAT-NA.
> To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org
>







----
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