Very long range non-line of sight

Is this possible with wi-fi at all? ~30kms range, curvature of earth alone
seems to prevent line of sight. ~512kbit throughput would be OK.

TIA,
Peter

"Peter" <(E-Mail Removed)> wrote in message news:<bot0v5$1hnqea$(E-Mail Removed)>...
> Is this possible with wi-fi at all? ~30kms range, curvature of earth alone
> seems to prevent line of sight. ~512kbit throughput would be OK.
>
> TIA,
> Peter


The maximum transmitting distance for any wireless transmissions above
about 30MHz (which includes 802.11, Wi-Fi) is determined by:

D = Sqrt(2*H)

Where:
D = maximum distances (in miles)
H = The height above ground for your transmitting antenna (in feet)

So if your access point is sitting on the 2nd floor of your house,
that's about 15 feet high. So if you put that into the equation you
get:

D = Sqrt(2*15)
D = Sqrt(30)
D = 5.47 Miles

5.47 miles = 8.8 Kilometers.

So in reality unless you built a huge antenna on your house, no matter
how much power you put out, the curve of the earth won't allow you to
transmit that far.

"Jeff Moon" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed) om...
> "Peter" <(E-Mail Removed)> wrote in message
news:<bot0v5$1hnqea$(E-Mail Removed)>...
> > Is this possible with wi-fi at all? ~30kms range, curvature of
earth alone
> > seems to prevent line of sight. ~512kbit throughput would be OK.
> >
> > TIA,
> > Peter
>
>
> The maximum transmitting distance for any wireless transmissions
above
> about 30MHz (which includes 802.11, Wi-Fi) is determined by:
>
> D = Sqrt(2*H)
>
> Where:
> D = maximum distances (in miles)
> H = The height above ground for your transmitting antenna (in feet)
>
> So if your access point is sitting on the 2nd floor of your house,
> that's about 15 feet high. So if you put that into the equation you
> get:
>
> D = Sqrt(2*15)
> D = Sqrt(30)
> D = 5.47 Miles
>
> 5.47 miles = 8.8 Kilometers.
>
> So in reality unless you built a huge antenna on your house, no
matter
> how much power you put out, the curve of the earth won't allow you
to
> transmit that far.
Ey up how long has the earth been round?

In article <(E-Mail Removed) >,
Jeff Moon <(E-Mail Removed)> wrote:
:The maximum transmitting distance for any wireless transmissions above
:about 30MHz (which includes 802.11, Wi-Fi) is determined by:

= Sqrt(2*H)

:Where:
= maximum distances (in miles)
:H = The height above ground for your transmitting antenna (in feet)

Jeff, when I plow through the algebra, I get a result which is
about 5/6 times what your formula would calculate. But
it would depend on the assumptions, so let's cross-check: for the
formula you show to hold, is the assumption that the transmitter and
receiving are both at height H above the ground (relative to the local
'down')? Or does the formula assume that the transmitter is at ground
level and the receiver at that height? Also, which distance is that
formula measuring: the straight-line distance from the transmitter
to receiver, or the curvilinear distance around the Earth from the
transmitter to the base of the receiver pole?

The formula I get for the case where the transmitter is at ground
level is D = Sqrt(H^2 + 2RH) / 5280 where D is in miles, and H and
R are in feet, and R is the radius of the Earth. If one says that
R >> H then H^2 effectively vanishes compared to 2RH, allowing the
simplification D = Sqrt(2RH)/5280 . If one lets r be the radius of
the Earth in miles, then D = Sqrt(2rH * 5280) / 5280 and then
D = Sqrt(2H) * Sqrt(r/5280). r is about 3963 so the multiplier comes
out about 0.866, which is roughly 5/6.

D ~= 5/6 Sqrt(2*H)
--
millihamlet: the average coherency of prose created by a single monkey
typing randomly on a keyboard. Usenet postings may be rated in mHl.
-- Walter Roberson

"Peter" <(E-Mail Removed)> wrote in message
news:bot0v5$1hnqea$(E-Mail Removed)...
> Is this possible with wi-fi at all? ~30kms range, curvature of earth alone
> seems to prevent line of sight. ~512kbit throughput would be OK.
>
Mostly you just need a couple of mountains to stand on. In the West they do
line-of-sight microwave between mountain peaks at distances much greater
than this.

In article <IFCsb.36034$(E-Mail Removed)>,
Ross Evans <(E-Mail Removed)> wrote:

:"Peter" <(E-Mail Removed)> wrote in message
:news:bot0v5$1hnqea$(E-Mail Removed)...
:> Is this possible with wi-fi at all? ~30kms range, curvature of earth alone
:> seems to prevent line of sight. ~512kbit throughput would be OK.

:Mostly you just need a couple of mountains to stand on.

By my calculation, 251 feet should do for the case of either the
receiver or transmitter being at ground level and the other of the
pair is elevated. See my analysis in another message in this thread.
--
Is "meme" descriptive or perscriptive? Does the knowledge that
memes exist not subtly encourage the creation of more memes?
-- A Child's Garden Of Memes

> > Is this possible with wi-fi at all? ~30kms range, curvature of earth
alone
> > seems to prevent line of sight. ~512kbit throughput would be OK.
> >
> Ignore all the calculations in relation to earth curvature - its a waste
of
> time (and a surprise to one person that the earth isn't flat).
>
> On a flat earth, you would get about 130dB of link loss in a perfect line
of
> sight - that¹s a bit much.
>
> Assume you get a receiver with 80dB sensitivity, you're still 50dB short.
>
> With a 13dB antenna and receiver, you'd need to pump out 0.4 watt
> approximately, which is way way way beyond the legal limits and would
> probably have people's pacemakers stopping (joke).
>
> If you want to break the land speed record, don't use a production motor
> car.
>
> If you want a 30km long link, use the right system - troposcatter or
> satellite and don¹t much around with WiFi.... It won't work in practice
> despite the calcualtions.

Sat is way out of price range. What is troposcatter? I assume some sort of
short-wave radio?

Thanks,
Peter

On 12/11/03 8:09 am, in article bot0v5$1hnqea$(E-Mail Removed),
"Peter" <(E-Mail Removed)> wrote:

> Is this possible with wi-fi at all? ~30kms range, curvature of earth alone
> seems to prevent line of sight. ~512kbit throughput would be OK.
>
Ignore all the calculations in relation to earth curvature - its a waste of
time (and a surprise to one person that the earth isn't flat).

On a flat earth, you would get about 130dB of link loss in a perfect line of
sight - that¹s a bit much.

Assume you get a receiver with 80dB sensitivity, you're still 50dB short.

With a 13dB antenna and receiver, you'd need to pump out 0.4 watt
approximately, which is way way way beyond the legal limits and would
probably have people's pacemakers stopping (joke).

If you want to break the land speed record, don't use a production motor
car.

If you want a 30km long link, use the right system - troposcatter or
satellite and don¹t much around with WiFi.... It won't work in practice
despite the calcualtions.

"Peter" <(E-Mail Removed)> wrote in message news:<bot0v5$1hnqea$(E-Mail Removed)>...
> Is this possible with wi-fi at all? ~30kms range, curvature of earth alone
> seems to prevent line of sight. ~512kbit throughput would be OK.
>
> TIA,
> Peter

Peter;

I'm sorry for all the nonsensical chatter and chest beating between
engineers. The short answer is no what you want to do is not possible
at the frequencies you are going to have to work with.

It would take a couple of towers to get you line of sight.

-m-

In article <BBDAEAC3.17C50%(E-Mail Removed)>,
Graham in Melton <(E-Mail Removed)> wrote:
:Ignore all the calculations in relation to earth curvature - its a waste of
:time (and a surprise to one person that the earth isn't flat).

:On a flat earth, you would get about 130dB of link loss in a perfect line of
:sight - that¹s a bit much.

:Assume you get a receiver with 80dB sensitivity, you're still 50dB short.

:With a 13dB antenna and receiver, you'd need to pump out 0.4 watt
:approximately, which is way way way beyond the legal limits and would
robably have people's pacemakers stopping (joke).

:If you want to break the land speed record, don't use a production motor
:car.

http://iwce-mrt.com/ar/radio_shootout_desert/

Contestants were expected to try to achieve the greatest
Wi-Fi/802.11b connection distance, using anything
from off-the-shelf hardware and commercial omni
directional antennas to highly improvised devices
built with $98 of Home Depot parts at the last
minute. Other Wi-Fi protocols, such as 802.11a
and 802.11g, were not permitted. Signal relaying
also was ruled out.

[...]

Adversarial Science Laboratory (ASLRulz, as they
prefer), won Category 6 and was the overall
distance winner, logging a transmission distance of
35.2 miles - more than two times longer than any
commercial entry


--
"There are three kinds of lies: lies, damn lies, and statistics."
-- not Twain, perhaps Disraeli, first quoted by Leonard Courtney