In your case I'm surprised it wasn't 16 as you obviously live in a universe far far removed from the norm.

There are 4 slots showing in mine but I've never seen more than two populated which stacks up with ignitionets statement that current VM Max is 400 (8 chan) down and 38 (2 chan) up. I wondered why they don't bond 3 if an area has 3 frequencies which I have seen mentioned. I've only ever seen 2 different frequencies in my own area 35.8 and 45.8 Mhz

In reply to a post by pcoventry76:

Is that the best you can do?

How droll.

It was 4 - just 4.

what frequencies? if you on the standard ones I believe that isnt possible, a discussion on CF suggested VM need to shift the frequencies to get a 4tth channel in.

In reply to a post by Chrysalis:

a discussion on CF suggested VM need to shift the frequencies to get a 4tth channel in.

That sounds very possible to me. They seen to be using 10MHz channel spacings so the high channel on the current scheme would be 55.8MHz which looks to be too close to the 60MHz I've seen mentioned as the highest frequency in the spec if the modulation uses the USB.

In reply to a post by kwikbreaks:

They seen to be using 10MHz channel spacings so the high channel on the current scheme would be 55.8MHz which looks to be too close to the 60MHz I've seen mentioned as the highest frequency in the spec if the modulation uses the USB.

USB?

The spec goes up to 85MHz subsplit and modulation isn't an issue.

The constraint is the physical plant. VM have areas with a few different subsplits Some top out at 50MHz, some at 65MHz, some at 85MHz. Some areas used to top out at 40 or even 30MHz but these were upgraded for the 10:1 ratio programme.

In between the DOCSIS 2 upstreams VM have DOCSIS 1.1 for STBs and legacy kit that barfs on 6.4MHz upstreams so how much room is left I'm not sure.

When you go from 2 to 3 or 4 upstream channels bonded it reduces the maximum transmit power the modem is allowed per channel by 3dB from 55.21dBmV to 52.21dBmV.

Sadly not as simple as just flicking a switch: plant has to be lined up to ensure as few modems as possible are in this range, then the outlying modems fixed.

EDIT: Here you go - hat tip to Cable Labs.

Edited by deleted (Wed 25-Sep-13 17:44:34)

Not relevant now after your answer to my question but by USB I meant upper sideband. Amplitude modulation of an RF signal results in two sidebands either side of the nominal channel frequency. Only one of the sidebands is needed to demodulate the signal and the old analogue TV used what is called vestigal sideband with the upper sideband used and the lower sideband mostly removed.

Not sure where I got 60MHz from but obviously it was wrong anyhow.