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Originally Posted by jrgagne99
I think in broad terms, amplifiers increase both components equally, so that the ratio of the usable signal to the noise (SNR) stays the same
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That is correct
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(except for a bit of added noise which is characterized by the amplifier's noise figure).
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The preamp does add its NF which reduces the SNR of the signal coming from the antenna, but on VHF the preamp noise and tuner noise are buried in the much higher amplified local noise. On UHF, a low-noise preamp might help because the preamp NF is lower than the tuner NF, but not usually on VHF, especially VHF-Low.
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So, amplifiers can't improve SNR between their input jack and their output jack since they amplify the whole signal (usable signal + noise) indiscriminantly.
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Correct