Max range for 802.11 (large distances)

Hi all,

I'm wondering what is the max distance that could be covered using a
802.11(b/g?) link over the sea and between two directive antennas
watching each other, considering the antennas are high enough, well
positionned.

Are there common power amplifiers usable in such cases ?
What throughput rate (signal strength) should I expect ?

Does rain affect the transmissions dramatically ?

I would greatly appreciate real-life experiences.


Thanks in advance.

Best regards,

Jerome.

In article <bui16r$nkp$(E-Mail Removed)>,
Jerome O. <(E-Mail Removed)> wrote:
: I'm wondering what is the max distance that could be covered using a
:802.11(b/g?) link over the sea and between two directive antennas
:watching each other, considering the antennas are high enough, well
ositionned.

Over the sea, hmmm.

Over the desert, someone is doing 100 Km, using 24 dBi antennas
at each end. Or so they claim.

oes rain affect the transmissions dramatically ?

It can, yes, but the effect depends on the kind of rain. A mist
is going to be worse than a rain -- the mist suspends a lot of water
vapour in the air, whereas raindrops just fall through the path and
are gone.

I suggest you check out the calculator at
http://my.athenet.net/~multiplx/cgi-...eless.main.cgi

According to that calculator, if you were to use antenna the height
of the CN Tower in Toronto Canada (553m) on both ends, then
your maximum distance would be somewhat less than 100 km. On the
other hand, when I put in the figures, I assumed the 1 Watt maximum
EIRP that is legal in the USA; your posting message ID suggests you are
in France, which has a -much- lower maximum power. I'm not sure that
you could get over the English Channel with the maximum you are allowed
in your area.
--
Inevitably, someone will flame me about this .signature.

"Jerome O." <(E-Mail Removed)> wrote:

> I'm wondering what is the max distance that could be covered using a
>802.11(b/g?) link over the sea and between two directive antennas
>watching each other, considering the antennas are high enough, well
>positionned.


There are reports of 20 miles or more. www.seattlewireless.org would be a good
place to start.

If you go to http://www.ecommwireless.com/calculations.html and select the first
link, you can do the calculations yourself. Keep in mind that the default noise
sensitivity is only good for 802.11b devices/speeds. You'll need to drop down to
68dB to get 802.11g connections.

Also, different Aps have different BER (noise) thresholds. The better ones are
lower.

Walter Roberson wrote:
> In article <bui16r$nkp$(E-Mail Removed)>,
> Jerome O. <(E-Mail Removed)> wrote:
> : I'm wondering what is the max distance that could be covered using a
> :802.11(b/g?) link over the sea and between two directive antennas
> :watching each other, considering the antennas are high enough, well
> ositionned.
>
> Over the sea, hmmm.
>
> Over the desert, someone is doing 100 Km, using 24 dBi antennas
> at each end. Or so they claim.
>
> oes rain affect the transmissions dramatically ?
>
> It can, yes, but the effect depends on the kind of rain. A mist
> is going to be worse than a rain -- the mist suspends a lot of water
> vapour in the air, whereas raindrops just fall through the path and
> are gone.
It's rather some kind of intensive tropical rain, in a very wet (80 to
100%) climate.. No mist.

> I suggest you check out the calculator at
> http://my.athenet.net/~multiplx/cgi-...eless.main.cgi
> According to that calculator, if you were to use antenna the height
> of the CN Tower in Toronto Canada (553m) on both ends, then
> your maximum distance would be somewhat less than 100 km. On the
> other hand, when I put in the figures, I assumed the 1 Watt maximum
> EIRP that is legal in the USA; your posting message ID suggests you are
> in France, which has a -much- lower maximum power. I'm not sure that
> you could get over the English Channel with the maximum you are allowed
> in your area.
The power limit in france is something like 100 milliwatts.
I dont know the legal max power in the part of the world I'm interested
in. Will have to dive into law texts.

This calculator is great. I'm going to do some experiments.

Thanks for your help anyway, Walter !
Regards,
Jerome Oufella

In article <bujb84$q2j$(E-Mail Removed)>,
Jerome O. <(E-Mail Removed)> wrote:
|Walter Roberson wrote:
|> In article <bui16r$nkp$(E-Mail Removed)>,
|> Jerome O. <(E-Mail Removed)> wrote:

|> oes rain affect the transmissions dramatically ?

|> It can, yes, but the effect depends on the kind of rain. A mist
|> is going to be worse than a rain -- the mist suspends a lot of water
|> vapour in the air, whereas raindrops just fall through the path and
|> are gone.

|It's rather some kind of intensive tropical rain, in a very wet (80 to
|100%) climate.. No mist.

Ah. That hints to me that there might at times be noticable winds.
If so then you are going to run into difficulties keeping the
antenna aligned. Or perhaps even keeping the antenna up at all.


I ran into some material a couple of months ago describing wiring up
some valleys in the Sierras in California, which talked explicitly
about their experiences with storms. Unfortunately I cannot recall
at the moment exactly which project that was. It's on the tips
of my fingers...
--
"There are three kinds of lies: lies, damn lies, and statistics."
-- not Twain, perhaps Disraeli, first quoted by Leonard Courtney

Jerome O. wrote:

> I'm wondering what is the max distance that could be covered using a
> 802.11(b/g?) link over the sea and between two directive antennas
> watching each other, considering the antennas are high enough, well
> positionned.

We have customers who have built reliable links for up to 18km. Don't
know the net speed though.
Over-sea links are ideal because the ground reflection helps in building
up a near perfect fresnel zone. Usually microwave links over sea work
dramatically better than over land.


> Are there common power amplifiers usable in such cases ?

Yes, but mostly illegal in EU countries.


> What throughput rate (signal strength) should I expect ?

1-2MBit/s

> Does rain affect the transmissions dramatically ?

Define dramatically. Yes it can, if it's so strong as you wrote in
another posting.

Regards,
Ekki

1000 mWatts (1 watt) is the LEGAL limit at 2.4 ghz as far as I know.

30 dBm that is.


As long as you are within that, you can do as you please which would include
jamming

"Ekki Plicht" <(E-Mail Removed)> wrote in message news:bumat6$n39$(E-Mail Removed)...
> Jerome O. wrote:
>
> > I'm wondering what is the max distance that could be covered using a
> > 802.11(b/g?) link over the sea and between two directive antennas
> > watching each other, considering the antennas are high enough, well
> > positionned.
>
> We have customers who have built reliable links for up to 18km. Don't
> know the net speed though.
> Over-sea links are ideal because the ground reflection helps in building
> up a near perfect fresnel zone. Usually microwave links over sea work
> dramatically better than over land.
>
>
> > Are there common power amplifiers usable in such cases ?
>
> Yes, but mostly illegal in EU countries.
>
>
> > What throughput rate (signal strength) should I expect ?
>
> 1-2MBit/s
>
> > Does rain affect the transmissions dramatically ?
>
> Define dramatically. Yes it can, if it's so strong as you wrote in
> another posting.
>
> Regards,
> Ekki
>

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

>1000 mWatts (1 watt) is the LEGAL limit at 2.4 ghz as far as I know.

But that's at the antenna output and only in the US. 1000mW through a 16 dB Yagi
or 24dB parabolic is a definite no no and will get you attention from the guys
with no sense of humor...

.. wrote:
> 1000 mWatts (1 watt) is the LEGAL limit at 2.4 ghz as far as I know.
>
> 30 dBm that is.

In the US, yes.
In EU thats 100mW or 20dBm EIRP.

In article <(E-Mail Removed)>,
Clark W. Griswold, Jr. <73115 dot 1041 at compuserve dot com> wrote:
:"." <(E-Mail Removed)> wrote:

:>1000 mWatts (1 watt) is the LEGAL limit at 2.4 ghz as far as I know.

:But that's at the antenna output and only in the US. 1000mW through a 16 dB Yagi
r 24dB parabolic is a definite no no and will get you attention from the guys
:with no sense of humor...

Somewhere in one of these threads, a few hours ago, I posted the exact
FCC limits. They depend upon which kind of frequency hopping you
are using. The more generous limit is for 1000 mW power input -to-
the antenna, with a 6 dBi gain allowed (ie., total 4000 mW EIRP),
and in the case of fixed point-to-point links, you can increase the
EIRP arbitrarily high by reducing the power input to the antenna.
It works out that for each 3 dBi you reduce the power to the antenna,
you can increase the antenna gain by 9 dBi, leaving a 6 dBi net
EIRP increase. Feed 0 dBi into the antenna and you could use a
900 dBi antenna ;-)

--
Caution: A subset of the statements in this message may be
tautologically true.