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*Subject*: Re: Fw: [amsat-bb] SUISAT forensics...The reverse procedure*From*: "John B. Stephensen" <kd6ozh@xxxxxxxxxxx>*Date*: Thu, 9 Feb 2006 09:42:37 -0000

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 > ========================================= > ---- > Sent via amsat-bb@amsat.org. Opinions expressed are those of the author. > Not an AMSAT member? Join now to support the amateur satellite program! > To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org [demime 1.01d removed an attachment of type image/jpeg which had a name of background noise.JPG] ---- Sent via amsat-bb@amsat.org. Opinions expressed are those of the author. Not an AMSAT member? Join now to support the amateur satellite program! To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org

**Follow-Ups**:**Re: Fw: SUISAT forensics...The reverse procedure***From:*i8cvs

**Re: Fw: SUISAT forensics...The reverse procedure***From:*Edward R. Cole

**References**:**Re: Fw: SUISAT forensics...The reverse procedure***From:*Edward R. Cole

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