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Originally Posted by qasdfdsaq
... The tuner may not be 8 channels wide (i.e. exactly 40Mhz). Remember the VMNG300 had a 126Mhz tuner, even though it "could" only use 20Mhz of the bandwidth, ….. Though I'm not sure how you know the SH's tuner is 16 channels wide. I can't find any info on it myself...
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Probably my oncoming dementure but this explanation seems a tad ambiguous / confusing and not easily related to CableLabs (Euro)DOCSIS specs?
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?
Quote:
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Originally Posted by Sephiroth
...Your SH currently sees a spread of 16 DS channels (each 8 MHz wide) in your set from which you can actually use 4 or 8 (or whatever VM set) according to the valid BPI+ key associated with your lease..
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Again that implies a Vendor RCP as either a single Receiver Module would need a 16 x 8 = 128MHz capture window or possibly more than one Receiver module? eg:
I'm also struggling with relating the "BPI+" to the RCP exchange at the moment as well?
Overall I still find the original "power" explanation a tad incongruous as depending on the modulation profile on each channel I find it somewhat difficult to conceive where you could have an average channel power(and the 3dB multiplier) that exceeds the max input spec of 33dBmv in any scenario that either doesn't already exceed +/- 17dBmv limit for a single channel or consequently doesn't then have extreme equalisation issues between individual channels anyway?
If however you perversely added the individual channel powers and then say deducted the 3dB uplift for doubling the channels you could more easily fit the scenarios?