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R: More about noise on AO40




----- Original Message -----
From: Paolo L. Stradiotto R. YV1DIG <paolo@yv1dig.org>
To: <amsat-bb@AMSAT.Org>
Sent: Wednesday, August 27, 2003 7:57 AM
Subject: [amsat-bb] More about noise on AO40


> Curiously today at 0530 UTC a strange steady carrier was on MB+30.
> After that i found a cw CQ on 145300.7 (MB-20) very weak , should has been
> close to a S1 or less, the
> station CQing was I1PIK and after that i found him with a S6 signal on
> 145341 (MB+20), checked again
> on MB-30 and i found he was on both freq at same time with different
signal
> levels. (0534 UTC and MB in 145320.8).
> I looked for the "simetric" signal for the carrier mentioned above and i
> found it on MB-30.
> Could be fine to ask I1PIK what kind of uplink he was using at the time
and
> also try to look on the .TLM files if is possible to know if the carrier
was
> on the same uplink type.
> I try the same procedure with other stations i heard on the passband but
> nothing ... too few stations on to
> sustain a theory but this could be something to check.
>
>  73's Paul YV1DIG
> AMSAT-YV Tech advisor
>
>
Hi Paul YV1DIG,

The problem that you describes is due to intermodulation products generated
by transponder when two or more strong  signals are operating at the same
time in the passband.

Very often i hear extremely weak CW signals over my SSB QSO"s
above the beacon (intermod) but tuning about 50 KHz from it i found  very
strong signals (wanted signal) transmitted by the above CW station about
20 KHz belove the beacon.

If you are able to receive a CW signal due to intermod that is normally very
weak at -30 dB or more belove the wanted CW signal it means that you have
a very sensitive receiving system

In any case i have forwarded your message to i1PIK

73" de

i8CVS Domenico

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