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Re: AO-40 ordering antennas, downconverters



Domenico,

     I understand that under poor conditions (bad squint) it could make a
difference.  My experience has been that when squint is bad there is no one
on to work.  I believe his noise figure will be good enough to work 98% of
what is available.  Some people have the resources and the desire to spend
200% more to get the additional 2%.  I am happy they can, but for most of us
this is not a wise use of our resources.

73,
Joe
ka0yos@amsat.org

----- Original Message -----
From: "i8cvs" <domenico.i8cvs@tin.it>
To: "Gary "Joe" Mayfield" <gary_mayfield@hotmail.com>; "AA2AE"
<aa2ae@optonline.net>; "AMSAT-BB" <amsat-bb@AMSAT.ORG>
Sent: Wednesday, July 24, 2002 12:36 AM
Subject: R: [amsat-bb] 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
> > >
>
>
>
>
>
>
>
> ----
> Via the amsat-bb mailing list at AMSAT.ORG courtesy of AMSAT-NA.
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>
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