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R: AO-40 ordering antennas, downconverters



Joe,

If  the signal  to be copied is barely readable in to the noise and you
realize that someone is calling you but you cannot understand his call
letter or you cannot get your signal report........well if  the station to
be copied rises his uplink power by 2.13 dB ,let say from 50 watt to 82 watt
than you will get call letter and signal report.

To rise the power by 2.13 dB is equivalent to improve your S/N by 2.13 dB or
to switch from a receiving system with an overall NF of 1 dB to 0.6 dB

73" de i8CVS Domenico


----- Original Message -----
From: Gary "Joe" Mayfield <gary_mayfield@hotmail.com>
To: i8cvs <domenico.i8cvs@tin.it>; AA2AE <aa2ae@optonline.net>; AMSAT-BB
<amsat-bb@AMSAT.Org>
Sent: Wednesday, July 24, 2002 4:29 AM
Subject: Re: [amsat-bb] AO-40 ordering antennas, downconverters


> 2.13 dB is less than half an S unit.  Listen across any band, see if you
> really notice less than half an S unit.
>
> 73,
> Joe
> ka0yos@amsat.org
>
> ----- Original Message -----
> From: "i8cvs" <domenico.i8cvs@tin.it>
> To: "AA2AE" <aa2ae@optonline.net>; "AMSAT-BB" <amsat-bb@AMSAT.Org>
> Sent: Tuesday, July 23, 2002 7:59 PM
> Subject: R: [amsat-bb] AO-40 ordering antennas, downconverters
>
>
> >
> > ----- Original Message -----
> > From: AA2AE <aa2ae@optonline.net>
> > To: <amsat-bb@AMSAT.Org>
> > Sent: Tuesday, July 23, 2002 11:51 PM
> > Subject: [amsat-bb] AO-40 ordering antennas, downconverters
> >
> >
> > > Group
> > >
> > > The Transystem downconverter with 37db gain and 1db NF seems to
compare
> > well
> > > with the SSB Electronics UEK 3000 converter and it's a lot cheaper.
> > >
> > > Any comments on this set-up and antenna alignment/mounting tips
> welcomed.
> > >
> > > Thanks for all your help.
> > >
> > > 73, Tony - AA2AE
> > >
> >
> > Hi Tony AA2AE,
> >
> > Transystem downconverter NF=1 dB
> >
> > SSB Electronics UEK 3000 NF=0.6 dB
> >
> > How much improves the signal to noise ratio (S/N) switching from an
> overall
> > 1 dB NF to an overall 0.6 dB NF with the same antenna ?
> >
> > NF= 1 dB ; Noise factor F=1.259 ;Equivalent noise temperature =75 kelvin
> >
> > NF= 0.6 dB ; Noise factor F= 1.148 ;Equivalent noise temperature = 42
> kelvin
> >
> > Suppose that the cold sky temperature + temperature due to spillover is
10
> > kelvin
> >
> > With Transystem the overall T= 75+10=85 kelvin
> > With UEK3000  the overall     T= 42+10=52 kelvin
> >
> > Less noise using UEK3000 = 10 log     (52/85) = -2.13 dB
> >                                                              10
> >
> > or 2.13 dB improvement in signal to noise ratio using UEK 3000
> > against Transystem
> >
> > So Transystem seams not to compare well with UEK 3000 because the
> > S/N ratio improvement in dB is much more than the difference in dB
> > between the NF of the above converters particularly when the cold
> > sky temperature added to that due to spillover is very low.
> >
> > An improvement of  S/N=2.13 dB make the difference when squint angle
> > is very high and signals to be received are very weak because to be
> received
> > with a 3 dB best signal to noise ratio it is necessary to double the
> uplink
> > power.
> >
> > I hope this help a bit
> >
> > 73" de i8CVS Domenico
> >
> > > ----
> > > 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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