When I do proof of performance testing with a spectrum analyzer. I use a pre amp and a tunable bandpass filter. The H/P 8591C likes to see a minimum of +25db input for testing. Keep in mind that without removing the video at the modulator you will not be getting a true C/N reading. I have not used the DSAM, but my rule of thumb is that a SDA 5000 is usually about 2db lower than the analyzer for C/N readings. Of course the analyzer will be more accurate due to the gated feature using a quiet line to compensate for the modulation. Try dropping the tap value off the node to increase levels. Take a before and after to see if there is any difference. You should have at least 50db C/N at the node. I like to see 54to 55 if you run a tight headend.
PM me if you would like more info
Re: C/N Measurements
Member #: 52068
Registered: 4/19/2007
Posted:
125
Name:
Jim
Company:
RF Broadband Solutions
Occupation:
Consultant, Sweep/Ingress
Location:
East Coast
Experience:
~37 years
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