Point to point sharing of ADSL connection

I am too far away from my local British Telecom exchange to get ADSL
but I have found a willing partner who can get broadband and have been
looking at the options to link to his service via a wireless link. We
have direct line of sight with a distance of 1.5Km. I am looking at a
pair Netgear ANT24D18 Antennae for the purpose. One snag I have hit
is that the line of sight goes straight through national grid high
voltage electricity lines between two pylons. Does anyone know or can
anyone point me to a source of expertise that would tell me if the
electromagnetic field around the lines would screw up the wireless
transmission? I would hate to buy all the gear for it not to work for
this reason!

Chris <(E-Mail Removed)> wrote:
> I am too far away from my local British Telecom exchange to get ADSL
> but I have found a willing partner who can get broadband and have been
> looking at the options to link to his service via a wireless link. We
> have direct line of sight with a distance of 1.5Km. I am looking at a
> pair Netgear ANT24D18 Antennae for the purpose. One snag I have hit
> is that the line of sight goes straight through national grid high
> voltage electricity lines between two pylons. Does anyone know or can
> anyone point me to a source of expertise that would tell me if the
> electromagnetic field around the lines would screw up the wireless
> transmission? I would hate to buy all the gear for it not to work for
> this reason!

David Taylor is in the UK.
http://www.nodomainname.co.uk/Equati..._broadband.htm
I don't think power lines should be a problem.

--
---
Clarence A Dold - Hidden Valley (Lake County) CA USA 38.8,-122.5

On Wed, 22 Jun 2005 21:46:52 +0100, Chris
<(E-Mail Removed)> wrote:

>I am too far away from my local British Telecom exchange to get ADSL
>but I have found a willing partner who can get broadband and have been
>looking at the options to link to his service via a wireless link. We
>have direct line of sight with a distance of 1.5Km.

Be sure to do the math necessary to insure that you have a reliable
link.
http://terabeam.com/support/calculations/som.php
Aim for a fade margin or system operating margin of about 20dB.
Nothing worse than 10dB will work reliably. Your receiver sensitivity
will vary with connection speed.

>I am looking at a
>pair Netgear ANT24D18 Antennae for the purpose.

http://www.netgear.com/products/details/ANT24D18.php
Are you sure 18dBi is enough gain? You can get 24dBi from a dish
antenna with a narrower beamwidth (for interference reduction) and
12dB more fade margin. Do the math. If you're lost, kindly supply
what hardware you have to work with, something about the path, how
much coax cable you're going to use, and I'll work the numbers. See:

http://groups-beta.google.com/group/...c1f6360282a331
for an example of how it's done.

Also, be sure to do a site survey to insure that there are no other
802.11 systems around that might interfere, especially if they are
along the line of sight between the two endpoints.

>One snag I have hit
>is that the line of sight goes straight through national grid high
>voltage electricity lines between two pylons. Does anyone know or can
>anyone point me to a source of expertise that would tell me if the
>electromagnetic field around the lines would screw up the wireless
>transmission? I would hate to buy all the gear for it not to work for
>this reason!

You won't have any trouble from the power lines. If you use
horizontal polarization, the horizontal power lines will act as less
of a barrier. With at 24dBi gain dish, the beam width is about 7
degrees. At 1.5km, that's a 150 meter wide spot. A few cm of
blockage by the power lines isn't going to be noticed.

What you may get is some 2.4Ghz RF noise coming from the power lines.
There isn't much noise coming from the power lines, but the gain of
the antennas will increase its stength substantially. If your system
displays highly variable connection loss, it might be noise. It's
difficult to see and will require a spectrum analyzer and low-noise
amplfier with a big dish antenna to detect. I wouldn't be overly
concerned about it as such noise interference is rather rare.
However, if something goes wrong, look for it.


--
Jeff Liebermann (E-Mail Removed)
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 AE6KS 831-336-2558

Many thanks for the helpful advice. I'll study the detail and try and
work out the maths myself before coming back for more help. Thanks
again.

On Thu, 23 Jun 2005 09:30:11 -0700, Jeff Liebermann
<(E-Mail Removed)> wrote:

>On Wed, 22 Jun 2005 21:46:52 +0100, Chris
><(E-Mail Removed)> wrote:
>
>>I am too far away from my local British Telecom exchange to get ADSL
>>but I have found a willing partner who can get broadband and have been
>>looking at the options to link to his service via a wireless link. We
>>have direct line of sight with a distance of 1.5Km.
>
>Be sure to do the math necessary to insure that you have a reliable
>link.
> http://terabeam.com/support/calculations/som.php
>Aim for a fade margin or system operating margin of about 20dB.
>Nothing worse than 10dB will work reliably. Your receiver sensitivity
>will vary with connection speed.
>
>>I am looking at a
>>pair Netgear ANT24D18 Antennae for the purpose.
>
> http://www.netgear.com/products/details/ANT24D18.php
>Are you sure 18dBi is enough gain? You can get 24dBi from a dish
>antenna with a narrower beamwidth (for interference reduction) and
>12dB more fade margin. Do the math. If you're lost, kindly supply
>what hardware you have to work with, something about the path, how
>much coax cable you're going to use, and I'll work the numbers. See:
>
>http://groups-beta.google.com/group/...c1f6360282a331
>for an example of how it's done.
>
>Also, be sure to do a site survey to insure that there are no other
>802.11 systems around that might interfere, especially if they are
>along the line of sight between the two endpoints.
>
>>One snag I have hit
>>is that the line of sight goes straight through national grid high
>>voltage electricity lines between two pylons. Does anyone know or can
>>anyone point me to a source of expertise that would tell me if the
>>electromagnetic field around the lines would screw up the wireless
>>transmission? I would hate to buy all the gear for it not to work for
>>this reason!
>
>You won't have any trouble from the power lines. If you use
>horizontal polarization, the horizontal power lines will act as less
>of a barrier. With at 24dBi gain dish, the beam width is about 7
>degrees. At 1.5km, that's a 150 meter wide spot. A few cm of
>blockage by the power lines isn't going to be noticed.
>
>What you may get is some 2.4Ghz RF noise coming from the power lines.
>There isn't much noise coming from the power lines, but the gain of
>the antennas will increase its stength substantially. If your system
>displays highly variable connection loss, it might be noise. It's
>difficult to see and will require a spectrum analyzer and low-noise
>amplfier with a big dish antenna to detect. I wouldn't be overly
>concerned about it as such noise interference is rather rare.
>However, if something goes wrong, look for it.