wet overhead lines

How much more lossy is an overhead line in the wet than the dry?
--
robert w hall

In article <(E-Mail Removed)>, Martin Warby
<(E-Mail Removed)> 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

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

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

> In article <(E-Mail Removed)>, Martin Warby
> <(E-Mail Removed)> 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

In message <+(E-Mail Removed)>, robert w hall
<(E-Mail Removed)> writes
>In article <(E-Mail Removed)>, Martin Warby
><(E-Mail Removed)> 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

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" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed)...
> In message <+(E-Mail Removed)>, robert w hall
> <(E-Mail Removed)> writes
>>In article <(E-Mail Removed)>, Martin Warby
>><(E-Mail Removed)> 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

Martin Warby <(E-Mail Removed)> wrote:
> On Mon, 09 Aug 2004 11:21:21 +0100, robert w hall wrote:
>
>> In article <(E-Mail Removed)>, Martin Warby
>> <(E-Mail Removed)> 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

In article <(E-Mail Removed)>, Jock Mackirdy
<(E-Mail Removed)> writes
>In article <(E-Mail Removed)>, 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

In article <(E-Mail Removed)>, Stuart Turrell
<(E-Mail Removed)> 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

In article <(E-Mail Removed)>, 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