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Re: poor snr on ao 40 2nd note



Thanks for the response.  The problem with your exploration is that I should
be able to here the xponder noise and I carefully check for the xponder
noise and I could not here it. I have a feeling that my rx system is less
than optimum but I am at a loss where to look.

73 nick k5qxj
----- Original Message -----
From: "Scott Townley" <nx7u@mindspring.com>
To: "Nick Pugh" <quadpugh@bellsouth.net>
Cc: "Helmut Strickner" <hstr@gil.com.au>; <amsat-bb@AMSAT.Org>
Sent: Friday, September 21, 2001 10:45 AM
Subject: Re: [amsat-bb] poor snr on ao 40 2nd note


> Actually this fits my experience as well.
> I do not have nearly the receive system Nick has, but when the passband
> is on I regularly receive the MB about 8-10dB lower than "predicted"
> using the link budgets (specifically Marcus' spreadsheets).
> Signal strength measurements after calibrating my FT-726R S-meter with a
> service monitor, and also using a newer spectrum analyzer (w/ additional
> preamplification) to monitor MB.
> Although the overall signal S/N seems to be OK since I can regularly
> make SSB contacts at 62,000km w/o upsetting LEILA (and manually pointed,
> at that!).
> This is what generated my question earlier in the week about how the S2
> TX AGC function works (which was met btw with deafening silence...surely
> someone out there knows!).
> I have measured my 2' dish system at G/T of -0.4dB which exactly matches
> my estimates of 20.9dB gain and Tsys of 135K.  On a 2' dish a pointing
> error of 10dB=zero QSOs, not the case.
> The only thing I've been able to come up with so far is that the AGC
> function is affecting the MB TX power as well, but that doesn't make any
> sense architecturally (to me, anyway).
>
>
> Nick Pugh wrote:
> >
> > Helmut
> > pointing errors would explain the contradiction in sun noise and lack of
> > signal on ao 40 however the dish was manual peaked and made several
> > measurements
> >
> > nick
> >
> > ----- Original Message -----
> > From: "Helmut Strickner" <hstr@gil.com.au>
> > To: "Nick Pugh" <quadpugh@bellsouth.net>; <amsat-bb@AMSAT.Org>
> > Sent: Thursday, September 20, 2001 8:41 AM
> > Subject: Re: [amsat-bb] poor snr on ao 40 2nd note
> >
> > > I believe that you are having pointing problems with your 6 ft dish!
> > >
> > > Nick Pugh wrote:
> > >
> > > > Here is my set up
> > > >
> > > > 6 ft dish gain 31 db linear pol
> > > > DEM pre amp .85 db nf gain 17 db
> > > > AIDC 3733 lnb stub removed
> > > > 3 db loss coax between LNB and receiver
> > > > Yaesu 736 receiver
> > > >
> > > >
> > > > I am receiving 6db of sun noise  this implies g/t of 8 db
> > > >
> > > > I am receiving the MB  15 db above the noise with squint angle < 10
deg
> > > > range app 50 k km.I think that i should see the MB at 27 db above
the
> > > noise.
> > > > To put it another
> > > > way if i see 6 db of sun noise what should i see the MB with squint
> > angle
> > > <
> > > > than 10 deg range app 50 k km.
> > > >
> > >
> > >
> > > ----
> > > Via the amsat-bb mailing list at AMSAT.ORG courtesy of AMSAT-NA.
> > > To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org
> >
> > ----
> > 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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