British Expats - Goodbye Sky TV

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Re: Goodbye Sky TV

Quote:

Originally Posted by Domino (Post 11130277)

What :confused:
Only "nearly right" :thumbsup:

are you are saying that signal loss isn't due to resistance ??
:confused:
and are you saying that "induced" intereference such as a street light, a fridge or freezer or arc welding is going to cause the internet to run slow ??
:confused:
most of those are "local" problems and most of the BE people aren't watching Corrie whilst doing abit of arc welding on the side.
they show up as blips on a frequency analyser not as constant reason for the signal having problems getting to the end of the line - in the same way as a long hose pipe has difficulty in maintaining pressure at the end of the run.

seperation is generally good for the runs of telephone cable, even in Spain, induced interference is also generally rare - especially if the cables are more than 12 inches apart.
Thats one of the reasons for using twisted pair or mult-twisted pair.

hth

Yes - I explained what signal loss is due to. Resistance is essentially a DC issue and nothing to do with telephone wires carrying DSL signals.

No, induced interference anywhere on a local connection between the premises and DSLAM location (telephone exchange for ADSL/ADSL2+ or in a street cabinet for VDSL) will not cause the Internet to run slowly, as the internet isn't affected by a local connection - but it can reduce the bandwidth or 'speed' of any individual local connection. It doesn't show up as "blips on a frequency analyser" - it can reduce the speed because specific 4kHz channels that make up the total available signal bandwidth can be affected. Remove the interfering source and the effective speed can go up.

Just for fun ........, your next-door neighbour could be out the front arc-welding, close to where the telephone lines run ........so your Corrie could be ruined after all. You did ask !!!

Unfortunately the hosepipe analogy isn't useful here - the interfering source could be anywhere eg a generator on a road not far from the telephone exchange.

Twisted pair cable was invented more than 100 years ago to reduce the impact on telephone calls of electromagnetic interference from external sources and crosstalk between neighbouring pairs. Cables coming outfrom a telephone exchange could be carrying 100s or 1000s of pairs and these are then split off into smaller multipair cables - so there isn't any separation until close to an individual premises.

Re: Goodbye Sky TV

Quote:

Originally Posted by MikeJ (Post 11130825)

strictly speaking resistance applies to DC cables, impedance (or more accurately reactance) is the attributes of transmission wires.

ADSL over unscreened twisted pair (UTP) Cat3 cabling normally used for voice telephone cables can offer up to 4kms from the exchange (in ideal conditions), over Cat7 screened twisted pair (F/FTP or F/STP) can provide up to 12kms. I suspect that most of Spain outside the big conurbations are still UTP telephone cables.

The latest ISDN transmission technology is VSDL which can offer up to 400mbs at subscriber premises but uses a completely different topology to conventional telephone cables. It is based on a short local loop in twisted pair (between 16 to 20 premises) connected to a cabinet. The BT version Openreach uses fibre optic to cabinet (FTTC) technology to transmit the signals to the locality and VDSL local loop for the final connections. Telefonica have a limited deployment of VDSL in the Madrid region but I have no idea what the plans for wider deployment are - although, unlike the UK, the campo is likely to be quite low on the list.

Local electromagnetic interference can lead to 'slow' internet. This because TCP/IP protocol is essentially a packet switching protocol. DTV requires the packets to arrive in the correct order, and the transmission protocols for DTV have some very complicated algorithms to ensure that packets are in the right order and to compensate for missing packets (which can be caused by local interference) this takes a finite time and would appear as 'slow' internet. Actually the most common reason for 'slow' internet is insufficient bandwidth to support the data rates of DTV, which leads to packet dropping, correction attempts and buffering all of which can make live/streaming TV problematical in many areas outside the more highly cabled regions of Spain (and anywhere else for that matter). The best way to view HDTV is by downloading the program, local caching and viewing.

All of which, of course, requires a connection to the service provider.

Cat3 UTP was invented in the 90s for in-building data LANs, specified to carry data up to 10Mbps and possibly to 16Mbps, depending on the LAN protocol used. Cat 3 UTP isn't deployed in the external telephony network, but you might find it as part of a structured cabling system in buildings.

VDSL (or VHDSL) is a DSL standard.and nothing to do with ISDN.

Internet TV doesn't require the packets to arrive in the right order, so it's unlikely that TCP/IP would be used for streaming. TCP/IP can often introduce delays due to its flow control mechanisms. Internet TV doesn't like delays, and using TCP/IP could produce a worse viewing experience therefore UDP is normally used for streaming. However TCP/IP is most often used for downloading Internet TV for later viewing.