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June 27th 15, 05:50 PM
posted to sci.electronics.design,rec.radio.amateur.antenna
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Antenna Amplifier Noise Figure
On Sat, 27 Jun 2015 15:49:50 +0100, Jeff wrote:
For a particular NF the effect on the output s/n ratio is always the same regardless of the actual input s/n, until you get to the point where the signal vanishes in the noise, but even then it still holds true but you just can't see it. The signal will go up by the gain of the amplifier, and the noise will go up by the sum of *power* of the input noise times the gain and the noise power of the calculated from the NF times the gain. The noise powers being in watts calculated from the NF; in a 1Hz Bandwidth by convention. So its dB above kTB converted to watts if you are working with NF in dB. So for a particular NF the added noise is always the same, therefore the SNRin/SNRout holds, and is a standard definition of NF (not in dB). Jeff https://en.wikipedia.org/wiki/DBm Look at the last four entries in the table. ..and your point is??? ....between its shoulders. |
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