Cable frequencies.
 

As VM and other cable companies use closed circuit systems, are they able to use duplicate frequencies that eg DTT or satellite use, or doesn't it work like that?

Re: Cable frequencies.
 

Some frequencies, indeed a lot, for instance, the dropping of FM radio services and changing TV/FM diplexers for 5-1000Mhz isolators, was to free up additional frequencies for broadband expansion.

This is why high grade coaxial cable with excellent screening is essential to prevent egress/ingress - cheaper co-ax always skimps on braid coverage, allowing signal to leak from and into the cable.

Re: Cable frequencies.
 

Yes, my van has a sniffer and when I drive it detects leakages of rf from the virgin network and alerts the network department

Re: Cable frequencies.
 

So they do duplicate the use of frequencies, but have to ensure that there are no leaks from the system to prevent services outside of the cable system being affected?

Have I understood correctly?

Thanks.

Re: Cable frequencies.
 

Yep, they do. As it's a closed system, OFCOM does not regulate the frequencies they use. For that very reason the system has to be "watertight" for both ingress & egress. Even then, where Virgins networks exist close to high power terrestrial transmitters, some frequencies cannot be used.

Re: Cable frequencies.
 

Thanks, I thought that would be the case.

In this case does ingress mean the incoming signal and egress mean the return path?

Re: Cable frequencies.
 

Ingress is signal leaking into virgins network, egress is the opposite. That's why we should terminate open joints

Re: Cable frequencies.
 

Cheers :)