I have a few questions about the correct setup procedure for measuring C/N. Here's the story....
Before I was around the C/N for EOL testing (last active) was done using the SDA 5000 and the accepted process was to add 5db to the measurement the meter gave us. I don't know where the 5db addition started, but it was a standard practice.
Someone who didn't know about the history of this process and decided we wouldn't do it anymore. Our C/N measurements are between 40 and 45 when not adding 5db and using the SDA. The company standard was 46 for EOL actives so we weren't passing anymore.
Now the search was on to find out what we (the techs) were doing wrong to get these unacceptable results. Also the company standard for EOL C/N was raised to 49DB and through a process I was not privy to it was decided it is now alright to add 5db to our SDA 5000 reading again.
Now they are leaning towards us using a pre-selector to first reduce overall power and peak the video carrier. It has been found they get better numbers with both the SDA and Spectrum Analyzer using this method. We are using a tunable Pre-Selector and the process used to peak the video carrier is to tune until the video carrier is as high as they can get it with the audio being as low as possible. There is usually an A/V delta of about 45.
Expected numbers are 52db at the node and 49db at the EOL active which they have been able to get by tweeking the pre-selector until they get the number.
How is it suppose to be done? Where can I find supporting documentation?
Carrier to Noise Setup
Member #: 18833
Registered: 1996-2001
Posted:
4
Name:
Chris
Company:
Charter Communications
Occupation:
Senior System Tech
Location:
Minnesota
Personal:
early 60s
Experience:
~29 years
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