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*Subject*: Fw: [amsat-bb] SUISAT forensics...The reverse procedure*From*: "i8cvs" <domenico.i8cvs@xxxxxx>*Date*: Thu, 9 Feb 2006 00:31:22 +0100

----- 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 ---- 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:*Edward R. Cole

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