Why is VM Broadband different?

[Terry]

Here in Ireland, NTL and Chorus strung coax along soffits and slung sometimes between houses without a support wire.

It can be difficult to spot the difference between an underground cable and one intended for aerial distribution as the later has an integral steel messenger wire:

Viewed from the ground I think the messenger wire could be difficult to spot.

The inside diameter of the outer conductor of this cable is half an inch and the loss is ~6dB per 100 metres @ 550MHz.

The maximum frequency of a network is often dependent on its age as amplifier technology has improved over the years. The Belgian networks of the mid 70s, for example,  were limited to 300MHz whilst early UK networks, being that much later, went up to 450MHz.

By the 90s this had increased to 550MHz and shortly afterwards to 600MHz which had more than adequate capacity for the analogue services at the time.

When digital TV started the muxes were slotted into gaps in the existing analogue service but, of courser, as the number of muxes expanded and broadband internet increased the demands on available bandwidth, an upgrade was called for.

By this time, my company, Encom, later Bell Cablemedia and subsequently Cable & Wireless Communications, was using amplifiers with a bandwidth extending up to 865MHz but there was still a huge lot of 600MHz or less networks to be considered. By now we had become ntl: so we were looking at about half the UK cable network as would have been Telewest.

Upgrades are expensive, no matter how hard you try to avoid it but ntl: adopted a strategy of upgrading to 750MHz as the extra cable losses at this frequency meant that very little cabling would need to be upgraded - just a lot of new amplifiers had to be installed.

Now, of course, all the analogue services have gone, leaving a clear field for digital.

The forward path now covers 85 - 750MHz which, if the entire spectrum was used, would enable 83  8MHz muxes to be carried.