Cable Forum - 100M Power levels went up a notch and speed down?

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- - 100M : Power levels went up a notch and speed down? (https://www.cableforum.uk/board/showthread.php?t=33691022)

Re: Power levels went up a notch and speed down?

Horse,

TYhanks for the trouble you've gone to in elaborating the question. The BPI+ observation of mine can be ignored - it was a long winded way of sying "whatever is associated with your authorised config".

The "average power" explanation is a simplification (that I qualified) because the user sees only the channels posted by the modem stats. He/she takes an average, but has no idea what power level adheres to the hidden channels. So, to explain the concept, the "average" is introduced.

Your point about +/-17 dBmv introduces another sort of interesting observation. Wouldn't you say, looking at the upper end, that 17 dBmv is the limit in a well built modem after which leakage into adjacent channels occurs. 33 dBmv seems to me to be a "busting" point (using the +3dB method) beyond which it is utterly useless as distinct from the 17 dBmv point.

Re: Power levels went up a notch and speed down?

Quote:

Originally Posted by Sephiroth (Post 35509022)

â€¦..
Your point about +/-17 dBmv introduces another sort of interesting observation. Wouldn't you say, looking at the upper end, that 17 dBmv is the limit in a well built modem after which leakage into adjacent channels occurs. 33 dBmv seems to me to be a "busting" point (using the +3dB method) beyond which it is utterly useless as distinct from the 17 dBmv point.

Looks like an eminently pragmatic conclusion to meâ€¦. ;)

Re: Power levels went up a notch and speed down?

BTW if all channels averaged 17 dBmv, you'd hit 17+3+3+3+3 = 29 dBmv.

And Regency Fish Restauarant to you!!!

Re: Power levels went up a notch and speed down?

Quote:

Originally Posted by Sephiroth (Post 35509205)

BTW if all channels averaged 17 dBmv, you'd hit 17+3+3+3+3 = 29 dBmv.

And Regency Fish Restauarant to you!!!

Which is a far more technically reasonable correlation with max input of 33dBmv than my corrupted variant of your algorithm. viz a ludicrously absurd (17*16) -3 -3 -3 -3 = 260dBmv! ;)

That said if you applied my inverted logic then the more d/s bonded channels then the nearer to optimal 0dBmv you'd want the average.
Thus 16 x 2.8 -3 -3 -3 -3 = 32.8dBmv â€¦.and allowing for 8dBmv equalisation these could even range from -1.2 through +6.8 for the 16 channels? ;)

Curiously, coincidentally (yet conveniently) that almost aligns with node/platform optimal ranges!

Which only goes to prove that "a little knowledge is a dangerous thing" and some of us can "clone" anothers concepts and totally pervert the facts to fit our observations without a clue of what we're doing! ;)
Must go - there's a a buzzing again in my wall box! :dunce:

Hate fish - guess what the wifes cooked tonight! Poetic justiceâ€¦. ;)

Re: Power levels went up a notch and speed down?

What you on tonight, Horse?

Re: Power levels went up a notch and speed down?

Quote:

Originally Posted by horseman (Post 35509004)

1. The inference above could be interpreted that 8 channels is equivalent to 40MHz? Obviously 8 (euroDOCSIS 8MHz d/s) channels would be 64MHz capture window with 8 adjacent channel constraint and thus 40MHz corresponds to only 5 adjacent channels?. That (8 adj channel constraint) of course only applies to minimum Standard Receive Connection Profile and as I'm sure you know the CM initially transmits a minimum of both a Std RCP and a Vendor specific RCP to CMTS so perhaps you know for certain which one any specific CMTS is actually using?

2. Equally "VMNG300 has a 126MHz tuner but only 20MHz bandwidth" seems to make little sense to me as neither appear to relate to adjacent channel capture window? Clearly I've misunderstood the context, perhaps you'd be kind enough to clarify?

Duuuhhh... Somehow I managed to get 5Mhz channel width into my head instead of 8Mhz when doing those calculations... Serves me right for posting at 5am.