Because of the high maintenance needed to monitor and filter spammers from the RF Cafe Forums, I decided that it would
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Below are all of the forum threads, including all
the responses to the original posts.
Post subject: Noise from a Class C Amplifier Posted: Fri Jan 27, 2006 10:37 am
This might be a simple question, but I need some assistance. I am looking at the noise generated by a Class C
amplifier (to keep things simple, lets assume it is has a 10 watt amplifier) and how to measure it.
would like to know if anyone has some suggestions about how to analyze the noise (instead of measuring it, can I
perform some calculations and get an approximate answer?)
Finally, has anyone tried to simulate the noise
from a Class C amplifier?
Any information will be appreciated - websites, magazine articles, books, etc.
Post subject: Posted: Sun Jan 29, 2006 11:54 am
Joined: Mon Jun 27, 2005 2:02 pm
You can measure the output noise of the PA by using Spectrum Analyzer. You first have to measure the output
noise when the PA is off, this result will be used as reference point, you have to know the temperature at which
it was measured. Then turn on the PA and notice that the noise floor is increased. Make these measurements at the
The difference between the noise floors at both cases is the gain of the noise + PA´s Noise
Figure. Of course that the noise is also dependent on the BW of operation (RBW of the SA in this case) and the
temperature according to: Pn=kTB
After this calculation, you can deduce the self-contribution of the PA to
the noise measured.