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*Subject*: [amsat-bb] NF and sensitivity calculations made easy*From*: Bob Nielsen <nielsen@xxxxxx>*Date*: Mon, 21 May 2001 08:01:04 -0700*User-Agent*: Mutt/1.2.5i

In case the various formulas floating around are confusing some of you, (the articles referenced are several years old and not readily available) it all boils down to the relatively simple equation for noise power, N= KTB, where N is the noise power in watts, K is Boltzmann's constant (1.38062 x 10^-23 Joules per degree K), T is the temperature in Kelvin and B is the bandwidth in Hz. Since Boltzmann's constant was pounded into my head in a physics class some 40+ years ago, that number was all I have ever needed to remember in order to calculate noise power. Converting Boltzmann's constant to decibels give us -228.6 dBW/deg K/Hz. Converting to dBm adds 30 dB and converting to room temperature (20 C) adds another 24.4 dB to give -174.2 dBm, usually rounded off to -174 dBm. All you need to do next is add in the factors for the bandwidth, noise figure and S+N/N and you have your system sensitivity. -- Bob Nielsen, N7XY nielsen@oz.net Bainbridge Island, WA http://www.oz.net/~nielsen IOTA NA-065, USI WA-028S ---- 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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