[VHFcontesting] LNA Gain

[John Santillo]

Hello I'm looking for some advice.

 

I understand the benefits of a low noise LNA on system noise from a
mathematical prospective but how do you select the right amount of LNA gain?
I've seen "rules of thumb" for example that the gain should be 10dB over the
Noise Figure of the Receiver or coax insertion loss but I haven't seen
anything that mathematically explains the benefit of 15dB of LNA gain over
say 30dB of LNA gain.  If for example I have a long coax run with 20dB of
loss, do I need an LNA gain 10dB higher than the loss of the coax? If so how
do I represent this mathematically?

 

Any advice is appreciated.

 

 

73,

 

John

 <mailto:N2hmm at warwick.net>  n2hmm at warwick.net