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uk.telecom.broadband (UK broadband) (uk.telecom.broadband) Discussion of broadband services, technology and equipment as provided in the UK. Discussions of specific services based on ADSL, cable modems or other broadband technology are also on-topic. Advertising is not allowed.

Radio Frequecies



 
 
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  #1  
Old July 9th 06, 01:23 PM posted to uk.telecom.broadband
Reg Edwards
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Posts: 168
Default Radio Frequecies

Propagation of Broadband along telephone cables involves radio
frequencies.

This question is related to why the relatively short length of wire in
your house, between the long phone cable and equipment appears, in
some cases, to affect reliability.

Why is it that the length of drop-wire from the top of a pole into
your premises has little or no effect?

Does anybody know, approximately, what are the highest radio
frequencies involved with Broadband? In MHz.
----
Reg.


  #2  
Old July 9th 06, 02:51 PM posted to uk.telecom.broadband
Bob Eager
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Posts: 2,472
Default Radio Frequecies

On Sun, 9 Jul 2006 12:23:38 UTC, "Reg Edwards"
wrote:

Propagation of Broadband along telephone cables involves radio
frequencies.

This question is related to why the relatively short length of wire in
your house, between the long phone cable and equipment appears, in
some cases, to affect reliability.

Why is it that the length of drop-wire from the top of a pole into
your premises has little or no effect?


Because there's a lot more electrical noise inside the premises.

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  #3  
Old July 9th 06, 07:59 PM posted to uk.telecom.broadband
Alan
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Posts: 130
Default Radio Frequecies

In message , Bob Eager
wrote
On Sun, 9 Jul 2006 12:23:38 UTC, "Reg Edwards"
wrote:

Propagation of Broadband along telephone cables involves radio
frequencies.

This question is related to why the relatively short length of wire in
your house, between the long phone cable and equipment appears, in
some cases, to affect reliability.

Why is it that the length of drop-wire from the top of a pole into
your premises has little or no effect?


Because there's a lot more electrical noise inside the premises.



What about the electrical noise generated by motor vehicles with poor or
no suppression components on their electrical systems? Doesn't the n
metres of telephone wire hanging from the poles act as an aerial for
these transmissions?

[1] Albeit at different frequencies and power levels, my digital TV via
an aerial is affected badly when one of those fart sounding motor cycles
passes close by.
--
Alan
news2006 {at} amac {dot} f2s {dot} com
  #4  
Old July 9th 06, 08:07 PM posted to uk.telecom.broadband
Bob Eager
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Posts: 2,472
Default Radio Frequecies

On Sun, 9 Jul 2006 18:59:50 UTC, Alan wrote:

Because there's a lot more electrical noise inside the premises.


What about the electrical noise generated by motor vehicles with poor or
no suppression components on their electrical systems? Doesn't the n
metres of telephone wire hanging from the poles act as an aerial for
these transmissions?

[1] Albeit at different frequencies and power levels, my digital TV via
an aerial is affected badly when one of those fart sounding motor cycles
passes close by.


That interference tends to be spasmodic and I guess the error correction
can cope with it. But ADSL cables are often quite near more long-term
sources of interference, I guess...mains wiring, etc.
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  #5  
Old July 9th 06, 10:57 PM posted to uk.telecom.broadband
[email protected]
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Posts: 529
Default Radio Frequecies


On 9-Jul-2006, "Bob Eager" wrote:

That interference tends to be spasmodic and I guess the error correction
can cope with it. But ADSL cables are often quite near more long-term
sources of interference, I guess...mains wiring, etc.


Twisting the pairs reduces the effect of interference, the twists
aid cancellation at the next twist. Which is why we use twisted
pairs for street cabling, and in general for high frequencies.
Unfortunately a lot of the pre and post war cable is still under our
streets, it's ok for phones, but rather a poor pitch (about 7-12ins
twist) for BB.
The speeds "Up to" would be a lot better with decent quality cable,
but Ian Valance was more interested in his salary and pension
than BB, so BT ended up by losing it's monopoly on the ducts and
cabling. If BT had used it's monopoly position to run fibre to the curb,
we would all be better off, and BT could have sold off a lot of
its smaller exchanges, which would have been a nice little earner.
But the other side of the coin would have been BT having a
monopoly and higher prices.
  #7  
Old July 10th 06, 12:39 AM posted to uk.telecom.broadband
[email protected]
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Posts: 529
Default Radio Frequecies


On 9-Jul-2006, "Bob Eager" wrote:

All of which has little or no connection with the topic under
discussion...


Except that there are endless complaints here
about sync failures, many, or most, of which
are probably cable related problems.
IMHO the cabling we have isn't going to
deliver quality video, which FTC would have.
  #8  
Old July 10th 06, 01:28 PM posted to uk.telecom.broadband
Tim Clark
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Posts: 179
Default Radio Frequecies

In article ,
"Reg Edwards" writes:
Propagation of Broadband along telephone cables involves radio
frequencies.

This question is related to why the relatively short length of wire in
your house, between the long phone cable and equipment appears, in
some cases, to affect reliability.

....

One cause can be the quality of the cabling instalation in the house.
Poor quality or untwisted cabling could be one reason, badly made
junctions another. Combine either of those two with some "Y junctions"
to parallel up some extensions, a few left unterminated, and there's a
nice recipe for RF attenuation and noise.

--
Tim Clark
  #9  
Old July 10th 06, 06:00 PM posted to uk.telecom.broadband
PeterW
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Posts: 49
Default Radio Frequecies

Mark wrote in
:

On 09 Jul 2006 13:26:56 GMT, "We Are Devo!"
wrote:

on 09/07/2006 at 13:23:38 Reg Edwards wrote:

Does anybody know, approximately, what are the highest radio
frequencies involved with Broadband? In MHz.


50Khz - 1.1Mhz

....for ADSL.



Which is why it gets a lot worse in the winter I presume with those
continental MW stations all over the dial. I assume that the lines act as
aerials and inject a lot of this on top of the ADSL signal which makes the
s/n suffer badly. I noticed this last winter having gone to MAX in
November.

Peter
  #10  
Old July 10th 06, 07:48 PM posted to uk.telecom.broadband
[email protected]
external usenet poster
 
Posts: 529
Default Radio Frequecies


On 10-Jul-2006, PeterW wrote:

Which is why it gets a lot worse in the winter I presume with those
continental MW stations all over the dial. I assume that the lines act as
aerials and inject a lot of this on top of the ADSL signal which makes the
s/n suffer badly.


Not to mention all this RF being launched into say 100 pairs
of a 200 pair cable as the BB uptake grows. Crosstalk between
pairs can only get worse. Anybody got Near End Cross Talk (NEXT)
figures for the pre and immediate post war cabling?
 




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