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Re: 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
>
> > ----
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>
>
>
>
>
>
>
>
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