[amsat-bb] Re: Preamp location tech question
gzook at yahoo.com
Fri Dec 18 13:11:00 PST 2009
Putting the preamplifier at the antenna and not at the equipment end overcomes the "noise figure" and losses of the feedline. Putting the preamplifier after the feedline adds the "noise figure" and losses of the feedline to the signal.
Therefore, having the preamplifier at the antenna end is definitely better. However, whether or not the added complexity of having the preamplifier at the antenna end is worth the improvement in the signal to noise ratio of the signal is another matter. For things like e.m.e. every little bit helps and having the preamplifier at the antenna is worth it. For other applications one has to weigh the benefits of the placement of the preamplifier with the considerable added complexity.
--- On Fri, 12/18/09, i8cvs <domenico.i8cvs at tin.it> wrote:
Actually 50 feet of LMR400 adds 0.75 dB to the Noise Figure of your 144 MHz preamplifier and 1.35 dB to the Noise Figure of your 432 MHz preamplifier.
Why deteriorate the Noise Figure of your receiving system adding the losses of a coax cable between the antenna and preamplifier?
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