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Re: Fw: SUISAT forensics...The reverse procedure



Tsky is probably twice earth thermal noise levels at 144 MHz due to galactic
noise.

73,

John
KD6OZH

----- Original Message -----
From: "Edward R. Cole" <al7eb@acsalaska.net>
To: "i8cvs" <domenico.i8cvs@tin.it>; "AMSAT-BB" <amsat-bb@amsat.org>
Sent: Thursday, February 09, 2006 05:01 UTC
Subject: Re: Fw: [amsat-bb] SUISAT forensics...The reverse procedure


> Domenico,
>
> You, Tony AA2TX, and David G0MRF have all arrived with numbers near the
> same and mine.  I think that assures that the apparent signal is in the
low
> mw range and absolute accuracy is not really meaningful since S-meter
> readings can not be precisely peaked (taken quickly in real-life
situations).
>
> I do differ in a couple places in the analysis so I will mention them.
> There really is not point in debating them a lot.
>
> For Tsky I chose 275K as reasonable quiet sky temp at 144-MHz.  It
probably
> is somewhat higher due to the horizon being in the antenna main lobe since
> elevation was only 9-degrees.  That would only raise it to 290K.  I chose
> Ta = 40K as this is a very well designed eme array.  G/T = -2.68.  I think
> 1200K is too high, and I live in an area without man-made industrial RFI
to
> contribute to this.
>
> I calculated my Trx based on an ambient temp = -12C (261K) so I had Trx ~
> 46K, but who really cares as we were looking for a magnitude of
transmitter
> ERP not high accuracy (consider the receiver signal measurement accurracy
> as limiting).
>
> So I am came out with 1mw and you 2mw.  I think we agree that the power
> level is in the single digit mw's which is considerably below that
expected
> (500mw).
>
> Thanks for confirming my analysis.  I always learn a little by looking at
> the results produced by others.
>
> 73's Ed - KL7UW
>
>
> At 12:31 AM 2/9/2006 +0100, i8cvs wrote:
> >----- Original Message -----
> >From: "Edward R. Cole" <al7eb@acsalaska.net>
> >To: "i8cvs" <domenico.i8cvs@tin.it>; "Luc Leblanc VE2DWE"
> >lucleblanc6@videotron.ca>; "AMSAT-BB" <amsat-bb@amsat.org>
> >Sent: Wednesday, February 08, 2006 7:55 AM
> >Subject: Re: [amsat-bb] SUISAT forensics...
> >
> >>OK here are some numbers to crunch:
> >>My observations of Suitsat at approx 1104utc 4Feb.
> >>signal S+N/N = 12 dB  (3 s-units over noise floor)
> >>system NF = 0.74 dB
> >>antenna gain = 21.3 dBi (vert-pol)
> >>range at closest approach = 1354km
> >>FM mode (15KHz BW)
> >>elevation angle = 9 deg
> >>Tamb = -12C
> >
> >>Have fun!
> >>73's,
> >>Ed - KL7UW
> >
> >Hi Ed, KL7UW
> >
> >I have worked out your numbers as follows:
> >
> >Your signal (S+N)/N = 12 dB = 15.84 in power ratio so
> >your S/N= 10 log    (15.84-1) = 11.71 dB
> >                            10
> >
> >Your system Noise Figure NF= 0.74 dB and so your Noise Factor F
> >is
> >           (10/0.74)
> >F= 10                  =  1.185  in power ratio and the equivalent noise
> >temperature of your RX is Trx= (1.185-1) x 290 = 53.65 kelvin
> >
> >Your antenna gain = 21.3 dBi
> >
> >Your range of closest approach with Suitsat = 1354 km
> >
> >Your RX Band Width  (BW) = 15 kHz = 15.000 Hz
> >
> >We can compute the free attenuation L between you and Suitsat
> >
> >L = 32.44 + 20 log     145.99 + 20 log    1354 =  138.35 dB
> >                                10                           10
> >
> >We assume that the equivalent noise temperature Ta of your antenna
> >is Ta= 1200 kelvin including the thermal noise picked up from the cold
> >sky plus the thermal noise picked up from the side lobes looking at
> >the ground so that the power Psys of Noise Floor referred to the input
> >of your RX when the antenna is connected can be computed as follows:
> >
> >                                         -23
> >Psys =10 log   [ 1.38 x 10    x ( 53.87 + 1200 ) x 15000 = - 125.85 dBm
> >                      10
> >
> >
> >Adding to Psys the antenna gain of 21.3 dB is like to reduce the Noise
Floor
> >at the input of  your receiver by 21.3 dB so that we have - 147.15 dBm
> >
> >If we subtract the free space attenuation of 138.35 dB to the above Noise
> >Floor we get the EIRP necessary for Suitsat to be received on the ground
> >with a signal to noise ratio S/N= 0 dB or with the signal equal to the
noise
> >for a range of 1354 km so that
> >
> >-147.15 + 138.35 = -8.8 dBm   is  the EIRP of Suitsat for a S/N = 0 dB =
1
> >
> >Since you receive Suitsat with a S/N= 11.71 dB this implies  that the
> >EIRP of Suitsat is -8.8 + 11.71 = + 2.91 dBm and
> >
> >                                                         (10/2.91)
> >                     EIRP of Suitsat =  10                  =  1.95 mW
> >
> >about 1.95 mW considering all round off and all unknown effects
>
  --------------------------------
> >
> >Here the reverse calculation procedure starting from Suitsat coming
> >down to the ground station using your data and the computed data:
> >
> >Computed Suitsat EIRP........................+2.91 dBm
> >
> >Isotropic free space attenuation
> >over 1354 km...................................  - 138.35 db
>
  ---------------
> >Available power in to an isotropic
> >ground antenna.................................. - 135.44 dBm
> >
> >Receiving antenna gain.......................+ 21.30 dB
>
  ---------------
> >Available input power of ground
> >receiver ...............................................- 114.14 dBm
> >
> >Computed RX Noise Floor with
> >antenna connected.............................. - 125.85 dBm
>
  --------------
> >S/N ratio at receiver output.............. +  11.71 dB
> >
> >
> >Using your data and having already calculated the Suitsat EIRP to be
> >+ 2.91 dBm  = 1.95 mW the above inverse procedure demonstrates that if
> >your measured data are correct than it is correct that your S/N had to be
> >11.71 dB
> >
> >Best 73" de
> >
> >i8CVS Domenico
> >
> 73's,
> Ed - KL7UW
> =========================================
> http://www.qsl.net/al7eb - BP40iq
> 144-EME: FT-847, mgf-1801/1402, 4xM2-xpol-20, 170w
> 432-EME: FT-847, mgf-1402, 1x21-ele (18.6 dBi), 60w
> =========================================
> ----
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[demime 1.01d removed an attachment of type image/jpeg which had a name of background noise.JPG]
----
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