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Re: CMTS Upstream Frequencies

Typically we are at 22Mhz and 33Mhz running 16QAM and seeing a 25SNR upstream. So yes we fall in between CPD peaks.

You may have to look at your return combining like node(s) to uBr port ratio. Typically we are 1:1 combining on the upstream and some towns you may see as high as 3:1.

Things to double check

Confirm return is swept properly (you would be surprised on what you find)

Set the input to the node transmitter using Power Per Hertz formula. Very important when adding additional power the transmitters. If you span out the return and look from 5Mhz to 50Mhz you can tell if your clipping the laser. You may see a harmonic of your cable modems above 42Mhz, if you do then you have a level problem.

Our min specs : -37dBc CNR, 40dB C/I using a CW carrier at designed input levels to amps.


Use a 16QAM signal generator and confirm health of QAM on the upstream. As you mentioned the SNR on the CMTS is not real accurate, but a signal generator gives you a much better idea how your return is.


We are actually started exploring 64QAM up.


Good luck!
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Posted in reply to: CMTS Upstream Frequencies by mkatona
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