LNA's and ATTENUATORS, Contradictions?

[iMONITOR]

How does a "wide-band" LNA amplify the signal without increasing the noise?

How does an attenuator lower noise without lowering the signal?

 

[dlwtrunked]

How does a "wide-band" LNA amplify the signal without increasing the noise?

How does an attenuator lower noise without lowering the signal?

An LNA amplifies the signal but not *receiver* noise as the LNA is before the receiver. All receivers generate their own noise when receiving. An LNA with a better NF (Noise Figure) can allow one to get a better signal-to-ratio to receive signals. An attenator does not lower *receiver* noise but lowers signal level which may be too strong for the receiver. As implied above, "noise" can mean different kinds of noise and the relevant one when discussing LNAs is receiver noise generate in the receiver itself.

 

[iMONITOR]

An LNA amplifies the signal but not *receiver* noise as the LNA is before the receiver. All receivers generate their own noise when receiving. An LNA with a better NF (Noise Figure) can allow one to get a better signal-to-ratio to receive signals. An attenator does not lower *receiver* noise but lowers signal level which may be too strong for the receiver. As implied above, "noise" can mean different kinds of noise and the relevant one when discussing LNAs is receiver noise generate in the receiver itself.

Easy to understand now!

Thanks!

 

[dlwtrunked]

No problem. One needs a good noise figure and sufficient gain in an LNA to make it useful. And then too much gain or nearby strong signals can overload the receiver so in using an LNA, one may need to attenuate back a little that gain if now the gain is too much or use notch filters (starting with the FM broadcast band and then others) to weaken signals that are now too strong. Experimentation is needed to get "peak" performance since each environment is different.