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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.

wet overhead lines



 
 
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  #1  
Old August 9th 04, 12:01 PM posted to uk.telecom.broadband
robert w hall
external usenet poster
 
Posts: 242
Default wet overhead lines

How much more lossy is an overhead line in the wet than the dry?
--
robert w hall
  #2  
Old August 9th 04, 12:21 PM posted to uk.telecom.broadband
robert w hall
external usenet poster
 
Posts: 242
Default wet overhead lines

In article , Martin Warby
writes

On Mon, 09 Aug 2004 11:01:06 +0100, robert w hall wrote:

How much more lossy is an overhead line in the wet than the dry?


the lines should be insulated so the rain shouldn't make any
difference,what could make a difference though is if any water can enter
the joints (and I don't think this is much more of a problem than it is
for any other sort of line)

Martin Warby

Isn't water a lossy dielectric at 1MHz - and there is still a
significant field around a parallel pair conductor even if it's nominal
insulated...?
--
robert w hall
  #3  
Old August 9th 04, 01:01 PM posted to uk.telecom.broadband
Martin Warby
external usenet poster
 
Posts: 15
Default wet overhead lines


On Mon, 09 Aug 2004 11:01:06 +0100, robert w hall wrote:

How much more lossy is an overhead line in the wet than the dry?


the lines should be insulated so the rain shouldn't make any
difference,what could make a difference though is if any water can enter
the joints (and I don't think this is much more of a problem than it is
for any other sort of line)

Martin Warby
  #4  
Old August 9th 04, 03:18 PM posted to uk.telecom.broadband
Martin Warby
external usenet poster
 
Posts: 15
Default wet overhead lines

On Mon, 09 Aug 2004 11:21:21 +0100, robert w hall wrote:

In article , Martin Warby
writes

On Mon, 09 Aug 2004 11:01:06 +0100, robert w hall wrote:

How much more lossy is an overhead line in the wet than the dry?


the lines should be insulated so the rain shouldn't make any
difference,what could make a difference though is if any water can enter
the joints (and I don't think this is much more of a problem than it is
for any other sort of line)

Martin Warby

Isn't water a lossy dielectric at 1MHz - and there is still a
significant field around a parallel pair conductor even if it's nominal
insulated...?


I doubt a small amount of water (the water will tend to fall off cable
onto ground.but to test this you could try something along the following
lines

take a telephone extension cable and use modems diagnostics to get
attenuation and SNR

Place cable in a conatiner full of water (whilst still connected at both
ends and find the attenuation / SNR as before

Martin Warby
  #5  
Old August 9th 04, 04:23 PM posted to uk.telecom.broadband
Peter R Cook
external usenet poster
 
Posts: 42
Default wet overhead lines

In message , robert w hall
writes
In article , Martin Warby
writes

On Mon, 09 Aug 2004 11:01:06 +0100, robert w hall wrote:

How much more lossy is an overhead line in the wet than the dry?


the lines should be insulated so the rain shouldn't make any
difference,what could make a difference though is if any water can enter
the joints (and I don't think this is much more of a problem than it is
for any other sort of line)

Martin Warby

Isn't water a lossy dielectric at 1MHz - and there is still a
significant field around a parallel pair conductor even if it's nominal
insulated...?

Don't think it makes any difference

This is not a scientific test, but it is pouring down outside. I am
about 4-4.5km from the exchange. Overheads pretty much all the way.

Router Netgear (835G) reports currently
ADSL Link Downstream Upstream
Connection Speed 576 kbps 288 kbps
Line Attenuation 38 db 26 db
Noise Margin 30 db 30 db

Those look better than any I have seen before

Usuall figures are closer to

Line Attenuation 39-40 db 26 db
Noise Margin 26-28 db 30 db

Upstream doesn't seem to change much

Regards
--
Peter R Cook
  #6  
Old August 9th 04, 07:01 PM posted to uk.telecom.broadband
Stuart Turrell
external usenet poster
 
Posts: 37
Default wet overhead lines

Downstream Upstream
SNR Margin 38.5 11.0 dB
Line Attenuation 36.4 19.5 dB
Errored Seconds 1193 685
Loss of Signal 194 194
Loss of Frame 7 0
CRC Errors 8 45
Data Rate 576 288 kbps
Latency FAST FAST


thats for me just taken from perowne way in sandown.






"Peter R Cook" wrote in message
...
In message , robert w hall
writes
In article , Martin Warby
writes

On Mon, 09 Aug 2004 11:01:06 +0100, robert w hall wrote:

How much more lossy is an overhead line in the wet than the dry?

the lines should be insulated so the rain shouldn't make any
difference,what could make a difference though is if any water can enter
the joints (and I don't think this is much more of a problem than it is
for any other sort of line)

Martin Warby

Isn't water a lossy dielectric at 1MHz - and there is still a
significant field around a parallel pair conductor even if it's nominal
insulated...?

Don't think it makes any difference

This is not a scientific test, but it is pouring down outside. I am
about 4-4.5km from the exchange. Overheads pretty much all the way.

Router Netgear (835G) reports currently
ADSL Link Downstream Upstream
Connection Speed 576 kbps 288 kbps
Line Attenuation 38 db 26 db
Noise Margin 30 db 30 db

Those look better than any I have seen before

Usuall figures are closer to

Line Attenuation 39-40 db 26 db
Noise Margin 26-28 db 30 db

Upstream doesn't seem to change much

Regards
--
Peter R Cook



  #7  
Old August 9th 04, 07:18 PM posted to uk.telecom.broadband
Ian Stirling
external usenet poster
 
Posts: 807
Default wet overhead lines

Martin Warby wrote:
On Mon, 09 Aug 2004 11:21:21 +0100, robert w hall wrote:

In article , Martin Warby
writes

On Mon, 09 Aug 2004 11:01:06 +0100, robert w hall wrote:

How much more lossy is an overhead line in the wet than the dry?

the lines should be insulated so the rain shouldn't make any
difference,what could make a difference though is if any water can enter
the joints (and I don't think this is much more of a problem than it is
for any other sort of line)

Martin Warby

Isn't water a lossy dielectric at 1MHz - and there is still a
significant field around a parallel pair conductor even if it's nominal
insulated...?


I doubt a small amount of water (the water will tend to fall off cable
onto ground.but to test this you could try something along the following
lines

take a telephone extension cable and use modems diagnostics to get
attenuation and SNR

Place cable in a conatiner full of water (whilst still connected at both
ends and find the attenuation / SNR as before


For reasonable results, you'll need to dig up the phone line back to the
exchange, and put all that in the water
  #8  
Old August 9th 04, 08:36 PM posted to uk.telecom.broadband
robert w hall
external usenet poster
 
Posts: 242
Default wet overhead lines

In article , Jock Mackirdy
writes
In article , Robert w
hall wrote:
How much more lossy is an overhead line in the wet than the dry?


Are you referring to open wire lines or overhead cable?

overhead -
I tried playing with the standard transmission line formula for a
parallel line (assumed Z0=300 ohm), in a medium with a complex
dielectric constant (loss tangent of 5E-3, which is for water at 1MHz))
and convinced myself that there _could_ be a measurable effect over a
few km...

Bob
--
robert w hall
  #9  
Old August 9th 04, 08:38 PM posted to uk.telecom.broadband
robert w hall
external usenet poster
 
Posts: 242
Default wet overhead lines

In article , Stuart Turrell
writes
Downstream Upstream
SNR Margin 38.5 11.0 dB
Line Attenuation 36.4 19.5 dB
Errored Seconds 1193 685
Loss of Signal 194 194
Loss of Frame 7 0
CRC Errors 8 45
Data Rate 576 288 kbps
Latency FAST FAST


thats for me just taken from perowne way in sandown.



Thanks
But don't I need some comparison data (wet v dry...)

--
robert w hall
  #10  
Old August 9th 04, 10:00 PM posted to uk.telecom.broadband
Jock Mackirdy
external usenet poster
 
Posts: 78
Default wet overhead lines

In article , Robert w
hall wrote:
How much more lossy is an overhead line in the wet than the dry?


Are you referring to open wire lines or overhead cable?

--

Jock Mackirdy
Bedford


 




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