So you're saying that anyting less than 400mw on the other end will be
useless?

On 15 Jan 2006 11:20:53 -0800, "Tekmanx" wrote:
So you're saying that anyting less than 400mw on the other end will be
useless?
No, it only takes microwatts at the receiver to do the job. Start at
the receiver, not the transmitter. Ham radios with only a Watt or two
talk to the Space Shuttle (hundreds of miles) without too much
trouble.

73's
Richard Clark, KB7QHC

So what is it you would say determines wither or not my signal will be
received on the other end? I mean with just a regular soho wifi access
point in open space you can only communicate within a couple hundred
feet (That's open space). If gain/wattage isn't so important when we're
talking distance.. what is? Line of site? Are you saying that that I
can shoot my 30mw signal from my soho access point couple of miles?

On 15 Jan 2006 11:56:12 -0800, "Tekmanx" wrote:

So what is it you would say determines wither or not my signal will be
received on the other end? I mean with just a regular soho wifi access
point in open space you can only communicate within a couple hundred
feet (That's open space). If gain/wattage isn't so important when we're
talking distance.. what is? Line of site? Are you saying that that I
can shoot my 30mw signal from my soho access point couple of miles?

Ah!

Only 30 mW? So you were expecting the antenna to boost it to 400
without any loss of the 30 getting to the antenna?

Why it seems limited is in exactly the problem described as multipath.
All those echoes are roughly the same strength because you are sitting
down low near many reflecting surfaces. "Open space," is not always
so open unless you are sitting in a pasture. Simply because there are
no obstructions between you and your destination does not mean the
signal is not traveling by many, many different paths - in fact, it is
guaranteed.

As I said, this is more a receive problem.

73's
Richard Clark, KB7QHC

Ok, I 'think' I understand now :/

So what is it you would say determines wither or not my signal will be
received on the other end? I mean with just a regular soho wifi access
point in open space you can only communicate within a couple hundred
feet (That's open space). If gain/wattage isn't so important when we're
talking distance.. what is? Line of site? Are you saying that that I
can shoot my 30mw signal from my soho access point couple of miles?

I've spoken with a guy who has set up a number of reliable
point-to-point links in the Sacramento valley, using standard
unamplified off-the-shelf SOHO-type access points and/or PCI cards or
USB dongles. He said he achieves reliable performance, with a good
margin of signal strength to handle rain fade, etc., with no
amplifiers, over distances of as much as 5 miles.

The key to doing this are a clear line of sight, an antenna with high
directional gain at each end of the link, and careful aiming. Getting
the radio right up at the antenna (rather than at the end of a length
of coax) is also beneficial.

The carefully-aimed highly-directional antennas give you several
advantages, over a standard SOHO omni antennas. The directionality
increases the effective radiated power of the transmitter (50
milliwatts through a 20 dBi antenna is equivalent to 5 watts
isotropic), it increases the receiver's effective sensitivity by the
same degree, and it makes the receiver _less_ sensitive to
interference arriving from other angles (e.g. competing transmitters).

Also, with proper choice of antenna, you can select the signal's
polarization angle. Since most home and business access points seem
to use vertically-oriented antennas (and thus a vertically polarized
signal) you can reduce interference problems by using point-to-
point antennas which are horizontally polarized.

The guy I spoke with was not complementary about the idea of trying to
"blast" signals through by using high-power transmitters or
amplifiers, and blanketing a large area with the signal.

You can buy wire-dish parabolic antennas for the 2.4-gig ISM radio
band quite easily. I think I've seen 'em advertised as having 15 to
19 dBi of gain. One of these at each end of the link would be a good
place to start.

--
Dave Platt AE6EO
Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

Dave Platt wrote:
I've spoken with a guy who has set up a number of reliable
point-to-point links in the Sacramento valley, using standard
unamplified off-the-shelf SOHO-type access points and/or PCI cards or
USB dongles. He said he achieves reliable performance, with a good
margin of signal strength to handle rain fade, etc., with no
amplifiers, over distances of as much as 5 miles.

It's important to point out that using these extreme high gain antennas
with out a license is illegal in the U.S. The guy that invented the
"pringles can" antenna was an FBI agent so he was not prosecuted, but
if he had been an average citizen the FCC would have come after him.

Then the question becomes which if any of the 14 WiFi channels is
actually in the 2.4gHz ham band.

Here in Israel it's even worse. WiFi and terrestrial 2.4gHz ham activity
is limited to 100mw EIRP. If you use a gain antenna, you must reduce
the transmitter power proportionaly.

Geoff.
--
Geoffrey S. Mendelson, Jerusalem, Israel N3OWJ/4X1GM
IL Voice: (07)-7424-1667 IL Fax: 972-2-648-1443 U.S. Voice: 1-215-821-1838
The trouble with being a futurist is that when people get around to believing
you, it's too late. We lost. Google 2,000,000:Hams 0.

In article ,
Geoffrey S. Mendelson wrote:

Dave Platt wrote:
I've spoken with a guy who has set up a number of reliable
point-to-point links in the Sacramento valley, using standard
unamplified off-the-shelf SOHO-type access points and/or PCI cards or
USB dongles. He said he achieves reliable performance, with a good
margin of signal strength to handle rain fade, etc., with no
amplifiers, over distances of as much as 5 miles.

It's important to point out that using these extreme high gain antennas
with out a license is illegal in the U.S. The guy that invented the
"pringles can" antenna was an FBI agent so he was not prosecuted, but
if he had been an average citizen the FCC would have come after him.

Not strictly true, although your point is well taken.

It's true that WiFi equipment must be tested and certificated as a
system. Using an off-the-shelf gain antenna, cabled to an
off-the-shelf WiFi AP/card, will almost certainly void the
certification, and then using the device becomes technically illegal
under Part 15, and unless you have a license for another service which
allows it (e.g. Part 97 ham license) you could be cited for it.

There are commercial WiFi radios whose manufacturers have tested and
certificated them with such high-gain antenna systems, specifically
for point-to-point connections. If you buy one of their radios and
one of their antennas, you can use 'em within the Part 15 rules, and
you'll be fully legal.

It's not so much the antenna itself... it's the certification status
of the antenna/radio system, as well as the EIRP.

Then the question becomes which if any of the 14 WiFi channels is
actually in the 2.4gHz ham band.

Check the ARRL's "multi-media wireless" interest group pages for
details on this. My recollection is that there are one or two 802.11b
channels whose power spectra fall within the ham-band 2.4-gig
allocation and also fall outside of the ham 2.4-gig "weak signal"
bandplan segments.

Here in Israel it's even worse. WiFi and terrestrial 2.4gHz ham activity
is limited to 100mw EIRP. If you use a gain antenna, you must reduce
the transmitter power proportionaly.

There's a similar proviso here in the U.S., but for point-to-point
links it's not as severe as that. If I recall properly, for a
point-to-point link, once you exceed 1 watt EIRP, you have to subtract
one dB of transmitter power for each additional 3 dB of antenna gain
you throw into the equation.

--
pDave Platt AE6EO
Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

Uh.. I'm not in the US. I'm in the Bahamas. Totally different when it
comes to this stuff