500' through pines revisited

See the thread on 12-15 for background and other comments.

It turns out that we CAN clear a line of site between my house and the other
building we want to network. With modest pruning of branches and a couple
of small trees removed we would have a pretty reliable line of site even in
moderate winds.

Distance is about 700' from house to house.

Recommendations for the wireless bridges and for inexpensive directional
antennas that would do the job??
- Tom

"tkranz" <(E-Mail Removed)> wrote:

>It turns out that we CAN clear a line of site between my house and the other
>building we want to network. With modest pruning of branches and a couple
>of small trees removed we would have a pretty reliable line of site even in
>moderate winds.

Don't forget the signal fresnel effect. You will need to allow for a slight
"bulge" in the middle of the signal path.

What's your opinion on how wide a "window" we need through the trees? We
should be able to achieve an 8' to 10' diameter "hole" through the trees
without any trouble, but perhaps not much more than that.
- Tom

"Clark W. Griswold, Jr." <73115%2e1041%40compuserve%2ecom> wrote in message
news:(E-Mail Removed)...
> "tkranz" <(E-Mail Removed)> wrote:
>
> >It turns out that we CAN clear a line of site between my house and the
other
> >building we want to network. With modest pruning of branches and a
couple
> >of small trees removed we would have a pretty reliable line of site even
in
> >moderate winds.
>
> Don't forget the signal fresnel effect. You will need to allow for a
slight
> "bulge" in the middle of the signal path.

"tkranz" <(E-Mail Removed)> wrote in message
news:_x7Fb.502722$(E-Mail Removed)...
> What's your opinion on how wide a "window" we need through the trees? We
> should be able to achieve an 8' to 10' diameter "hole" through the trees
> without any trouble, but perhaps not much more than that.
> - Tom
>
According to the Fresnel calculator here:
http://www.ecommwireless.com/calculations.html , using the worst-case
assumption that the narrowest part of the "hole" is at the halfway point,
you would need ~ 6.5 feet on either side of the centerline.

"tkranz" <(E-Mail Removed)> wrote:

>What's your opinion on how wide a "window" we need through the trees? We
>should be able to achieve an 8' to 10' diameter "hole" through the trees
>without any trouble, but perhaps not much more than that.

You don't need an opinion - get the facts!

Try this web site for some great calculators:

http://www.ecommwireless.com/calculations.html

Specifically, look at the Simple Wireless Network Link Analysis and Fresnel Zone
Calculator links...

I did not catch the detail before this repost.

How does this range of frequencies behave, i.e. 2.4G, meaning does this have
to be truly line of site with no obstruction. My thoughts are that going
through any wooded area, things change meaning leaves, branches, foliage,
etc. How mindful does one have to be of the obstructions. I wouldn't
expect to be able to go through a steel structure but would minor
obstructions such as small branches and foliage cause an issue?



"Clark W. Griswold, Jr." <73115%2e1041%40compuserve%2ecom> wrote in message
news:(E-Mail Removed)...
> "tkranz" <(E-Mail Removed)> wrote:
>
> >It turns out that we CAN clear a line of site between my house and the
other
> >building we want to network. With modest pruning of branches and a
couple
> >of small trees removed we would have a pretty reliable line of site even
in
> >moderate winds.
>
> Don't forget the signal fresnel effect. You will need to allow for a
slight
> "bulge" in the middle of the signal path.

"andyf" <(E-Mail Removed)> wrote:

>How does this range of frequencies behave, i.e. 2.4G, meaning does this have
>to be truly line of site with no obstruction. My thoughts are that going
>through any wooded area, things change meaning leaves, branches, foliage,
>etc. How mindful does one have to be of the obstructions. I wouldn't
>expect to be able to go through a steel structure but would minor
>obstructions such as small branches and foliage cause an issue?

You will see significant signal loss if there is *any* obstruction. The
obstruction does not have to be line of sight. The "bulge" or fresnel effect
means that for runs of 500' or so, you will need 5-6' of clearance around the
LOS.

In article <(E-Mail Removed)>,
Clark W. Griswold, Jr. <73115%2e1041%40compuserve%2ecom> wrote:
:"andyf" <(E-Mail Removed)> wrote:

:>How does this range of frequencies behave, i.e. 2.4G, meaning does this have
:>to be truly line of site with no obstruction. My thoughts are that going
:>through any wooded area, things change meaning leaves, branches, foliage,
:>etc. How mindful does one have to be of the obstructions. I wouldn't
:>expect to be able to go through a steel structure but would minor
:>obstructions such as small branches and foliage cause an issue?

:You will see significant signal loss if there is *any* obstruction.

Adding to what Clark said:

At 2.4 GHz, foliage is a significant problem. That frequency range
is absorbed by water relatively easily, and foliage contains a fair bit
of water and holds it right there in the line of sight.

2.4 GHz is not the frequency at which water most easily absorbs energy,
but in that frequency range, -most- of the radio energy is absorbed by
water fairly easily.
--
This is not the same .sig the second time you read it.

On Tue, 23 Dec 2003, Walter Roberson wrote:
> In article <(E-Mail Removed)>,
> Clark W. Griswold, Jr. <73115%2e1041%40compuserve%2ecom> wrote:
> :"andyf" <(E-Mail Removed)> wrote:
>
> :>How does this range of frequencies behave, i.e. 2.4G, meaning does this have
> :>to be truly line of site with no obstruction. My thoughts are that going
> :>through any wooded area, things change meaning leaves, branches, foliage,
> :>etc. How mindful does one have to be of the obstructions. I wouldn't
> :>expect to be able to go through a steel structure but would minor
> :>obstructions such as small branches and foliage cause an issue?
>
> :You will see significant signal loss if there is *any* obstruction.
>
> Adding to what Clark said:
>
> At 2.4 GHz, foliage is a significant problem. That frequency range
> is absorbed by water relatively easily, and foliage contains a fair bit
> of water and holds it right there in the line of sight.

PS: Microwave ovens operate at 2.45 GHz for a reason.....

> 2.4 GHz is not the frequency at which water most easily absorbs energy,
> but in that frequency range, -most- of the radio energy is absorbed by
> water fairly easily.

PPS: And for an oven, that energy is translated into heat.

In article <(E-Mail Removed)> ,
D. Stussy <(E-Mail Removed)> wrote:
|On Tue, 23 Dec 2003, Walter Roberson wrote:

|PS: Microwave ovens operate at 2.45 GHz for a reason.....

|> 2.4 GHz is not the frequency at which water most easily absorbs energy,
|> but in that frequency range, -most- of the radio energy is absorbed by
|> water fairly easily.

Yes, microwave ovens operate at that frequency in order for
the water in the food to absorb energy fairly quickly, but deliberately
not as efficiently as possible. It made sense once I read the
explanation: if a higher frequency had been used, the microwave
energy would be absorbed too close to the "skin" of the object, and
so would not be able to penetrate to inner water to heat it. They
thus deliberately engineered in some inefficiency in order for the
microwave energy to heat all the way through.


|PPS: And for an oven, that energy is translated into heat.

Yes, at 650 watts (popcorn oven) to 800 watts (smallest regular oven),
up to 1350 watts or so (big suckers); 1000 to 1100 watts being typical.
[1500 watts is about the maximum that could be drawn on a standard
North American 110 volt 15 amp house circuit.]

The frequency range used by 802.11b and 802.11g is limited to 1000 mW
(1 watt) in the USA and Canada, with noticably lower radio strengths
being common (e.g., 10 mW, 100 mW) to allow for about 3 dB of antenna
gain without exceeding the legal limit.

At that strength it would take about 10 1/2 days to boil a cup of
coffee near the antenna. At several hundred feet away, it'd be about
6 months. It might be enough of a temperature rise to be noticable
against a pattern of frost, but probably not otherwise.

--
"No one has the right to destroy another person's belief by
demanding empirical evidence." -- Ann Landers