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*Subject*: R: [amsat-bb] System NF Calculations*From*: "i8cvs" <domenico.i8cvs@xxxxxx>*Date*: Mon, 21 May 2001 14:56:12 +0200

The formula for NF calculation of my previous message must be corrected with the following one because i missed a square in to the numerator.The actual formula is correct Apologise from i8CVS Domenico ----- Original Message ----- From: i8cvs <domenico.i8cvs@tin.it> To: Bill Hurlock <bill@hurlock.net>; Scott Townley <nx7u@arrl.net> Cc: Joe Leikhim <jleikhim@nettally.com>; AMSAT-BB <amsat-bb@amsat.org> Sent: Monday, May 21, 2001 1:03 PM Subject: R: [amsat-bb] System NF Calculations > Hi Bill, > > The FT-736 sensitivity in CW/SSB with 2500 Hz bandwidth is -15 dB microvolt > for a ratio of (S+N)/N = 12 dB > from here: > > 10 log ( -15/20 ) = 0,177 microvolt > 10 > > This is the applied voltage across the receiver input necessary to obtain > an output with a ratio of (S+N)/N = 12 dB > > > > (12/10) > (S+N)/N =12 dB is equivalent to 10 = 15,84 in factor > > S+N > and S/N = -------- -1 =15,84-1= 14,84 in factor > N > > The noise figure in dB can be readily calculated using the following formula > derived from an article published in Ham Radio Magazine April 1980 page 71 > and 94 and titled "Noise Figure Relationship" > > -6 2 > ( 0,177x10 ) x 20 > NF (dB) = [ 10 log ------------------------- ] + 174 = > 10 2500 x 14,84 > > > = -167,7 + 174 = 6,27 dB > > In this formula 20 is a constant and 174 is the -174 dBm available thermal > noise power density (dBm in 1 Hz at room temperature) and 2500 is the > bandwidth in Hz > > > > 73 de i8CVS Domenico > > > ----- Original Message ----- > From: Bill Hurlock <bill@hurlock.net> > To: Scott Townley <nx7u@arrl.net> > Cc: Joe Leikhim <jleikhim@nettally.com>; <amsat-bb@AMSAT.Org> > Sent: Sunday, May 20, 2001 11:56 PM > Subject: Re: [amsat-bb] System NF Calculations > > > > I looked at the manual for the Ft-736R and it says for cw/ssb better than > > -15dbu for 12 db S=N:N. What does that make it. > > > > > ---- > > > 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. To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org

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