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Jim - NN7K wrote:
Generally speaking, the BEST NOISE figure (factor, ect. is what you want (best sensitivity), however, the Gain would be a consideration, IF you had excessive coax loss. (in this case, in excess of 16 dB, which would be quite doubtful. The gain of a vhf (or any amp, for that matter), only needs to exceed your coax (and your front end I.E. Reciever's Noise figure, so as to allow the preamps noise figure to take precidence (establish your floor sensitivity) I hope I stated that correctly. And, even then, as long as THAT noise figure is below the cold sky noise (from other sources), then the cold sky noise (about 1.8 dB on 2 meters) is the limiting factor on your sensitivity, before figureing the SELECTIVITY of your reciever (half the bandwidth, gain 6 dB, half again, now gain another 6dB). Probably as clear as mud, but the best I can describe it-- Jim -NN7K Great response, Jim. Only one nit to pick, that Noise Figure and incoming noise energy are not equivalent or even really related. Also, a .1 dB change in NF does not imply a .1dB change in signal to noise or received signal level. It is a non-intuitive relationship to say the least. tom K0TAR |
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