HOW TO MEASURE THE CARRIER-TO-NOISE RATIO AT THE OUTPUT OF AN AMPLIFIER
Spectrum analyzer (SA)
Method of measurement:
Connect the antenna to the input of the amplifier and power it.
Connect the SA to the output.
Set the equipment controls so as to be able to see the channel(s) that are to be tested.
First of all, set the SA as follows:
Record this measured value: C output.
Now select a portion of the output band with only noise, and set new SA parameters:
This value will be: 10 log 5/1= 7 dB.
This is the real noise level N output carrier = (N output - 7) dB.
Finally, calculate the C/N by subtracting this value from the value recorded previously:
C/N output = C output - N output carrier = C output - N output - 7 dB.