PLEASE HELP - Need advise (thats legal!)

I am trying to create a multi-point wireless network. The main server
will be 10km away. I do have LOS. This sight will be having a
OMNI-DIRECTIONAL antenna about 80ft above the ground (to clear and
obstuctions). Once of the recieving ends (which is 10km away) will be
using a 24dBi parabolic Andrew antenna to try and link to the
OMNI-DIRECTIONAL antenna. Here is our delema.... We first considered
using a 15.4dBi omni 70inch antenna (from fab-corp.com) with a 1w
outdoor amp linked to a 200mw Long-Range 802.11b router. After finding
out that this was ILLEGAL.... (I'm assuming that it is harmful to ones
health). I would like to ask the experts in this group what is the
MOST powerful antenna I can use without breaking the law or causing
any kind of health concerns to prelonged exposure.

BTW: Here is some more info on the setup.
Both routers are the same (200mw Long Range 802.11b routers from
fab-corp.com)
24 dBi Andrew parabolic antenna (for the recieving end)
both routers will be using 1ft low loss cable from antenna to router
Also... from what I've read in this group... a 6dBi omni looks like
the maximum legal limit for this amp. So my question is.... would the
6dBi omni with the 1w amp be better than the 15.4dBi omni without the
amp???? If there is any better combo... please let me know.


Thanks!

> will be 10km away. I do have LOS. This sight will be having a
> OMNI-DIRECTIONAL antenna about 80ft above the ground (to clear and

Why will one end have an omni directional antenna? I don't follow that,
you should be using 2 directional antennas for a point to point link.

> the maximum legal limit for this amp. So my question is.... would the
> 6dBi omni with the 1w amp be better than the 15.4dBi omni without the
> amp???? If there is any better combo... please let me know.

I'm not in your country but I think you'll find that 2 24dBi parabolic
antennas will do the link without any amplification anyway for that
distance.

David.

David,

I have to repeat myself 1 million times everytime I post........ I
know 2 directional antennas would be more than enough.... for a point
to point. But this is NOT a point to point connection. This is a point
to MULTIPOINT connection....like I said earlier. I MUST (1000%
certainty) have a omni antenna on one end.


Thanks.... and please advise.

Kingz#1 wrote:
> I am trying to create a multi-point wireless network. The main server
> will be 10km away. I do have LOS. This sight will be having a
> OMNI-DIRECTIONAL antenna about 80ft above the ground (to clear and
> obstuctions). Once of the recieving ends (which is 10km away) will be
> using a 24dBi parabolic Andrew antenna to try and link to the
> OMNI-DIRECTIONAL antenna. Here is our delema.... We first considered
> using a 15.4dBi omni 70inch antenna (from fab-corp.com) with a 1w
> outdoor amp linked to a 200mw Long-Range 802.11b router. After finding
> out that this was ILLEGAL.... (I'm assuming that it is harmful to ones
> health). I would like to ask the experts in this group what is the
> MOST powerful antenna I can use without breaking the law or causing
> any kind of health concerns to prelonged exposure.
>
> BTW: Here is some more info on the setup.
> Both routers are the same (200mw Long Range 802.11b routers from
> fab-corp.com)
> 24 dBi Andrew parabolic antenna (for the recieving end)
> both routers will be using 1ft low loss cable from antenna to router
> Also... from what I've read in this group... a 6dBi omni looks like
> the maximum legal limit for this amp. So my question is.... would the
> 6dBi omni with the 1w amp be better than the 15.4dBi omni without the
> amp???? If there is any better combo... please let me know.
>
>
> Thanks!

Most people I know in the business stay away from amps unless it's the
*only* way to get it to work. Amps amplify noise equally with signal,
they don't always help. With 200mw radios, a 15dbi omni and a 24dbi
parabolic, I can hardly imagine you having problems getting a 10km link
to work unless there is a lot of 2.4GHz noise in the area already or you
have problems aiming the omni (you do know high-gain omnis have a rather
flat doughnut shaped radiation pattern, don't you?) Done a site survey yet?

"Kingz#1" <(E-Mail Removed)> schreef in bericht
news:(E-Mail Removed) om...
> I am trying to create a multi-point wireless network. The main server
> will be 10km away. I do have LOS. This sight will be having a
> OMNI-DIRECTIONAL antenna about 80ft above the ground (to clear and
> obstuctions). Once of the recieving ends (which is 10km away) will be
> using a 24dBi parabolic Andrew antenna to try and link to the
> OMNI-DIRECTIONAL antenna. Here is our delema.... We first considered
> using a 15.4dBi omni 70inch antenna (from fab-corp.com) with a 1w
> outdoor amp linked to a 200mw Long-Range 802.11b router. After finding
> out that this was ILLEGAL.... (I'm assuming that it is harmful to ones
> health). I would like to ask the experts in this group what is the
> MOST powerful antenna I can use without breaking the law or causing
> any kind of health concerns to prelonged exposure.
>
> BTW: Here is some more info on the setup.
> Both routers are the same (200mw Long Range 802.11b routers from
> fab-corp.com)
> 24 dBi Andrew parabolic antenna (for the recieving end)
> both routers will be using 1ft low loss cable from antenna to router
> Also... from what I've read in this group... a 6dBi omni looks like
> the maximum legal limit for this amp. So my question is.... would the
> 6dBi omni with the 1w amp be better than the 15.4dBi omni without the
> amp???? If there is any better combo... please let me know.
>
>
> Thanks!

Your combined specifications are difficult to meet: multipoint wireless + 10
km distance + legal solution.
I guess that you need to let one spec go to make this work. The legal aspect
might be tied to health issues,
though I'd rather think it is a matter of interference. Wireless signals do
interfere and your strong signal
will disturb all the weaker ones it finds in its path. Depending on your
location, you might get away
with strong signales, as long as nobody else suffers. I live in the
Netherlands and for sure it would
be cause for complaints.
Signal amplification is the last thing I'd pursue. At the omnidirectional
side, the antenna receives a lot
of noise and that gets amplified as well. Amplifiers don't change the signal
to noise ratio, they make
it even worse.
Basically the only advice here is to change the multipoint design to a
collection of point-to-point
connections. It is very likely that you don't want to hear that, but please
remember that multipoint
is equivalent to a a single point of failure. Not a good design, but YMMV,
Hans

(E-Mail Removed) (Kingz#1) wrote in news:4d451e16.0406250822.48f38c00
@posting.google.com:

> David,
>
> I have to repeat myself 1 million times everytime I post........ I
> know 2 directional antennas would be more than enough.... for a point
> to point. But this is NOT a point to point connection. This is a point
> to MULTIPOINT connection....like I said earlier. I MUST (1000%
> certainty) have a omni antenna on one end.
>
>
> Thanks.... and please advise.
>

The max TX power is 36 dBm. So base your calculation's on that. 200 mW is
23 dBm. Assuming that the antenna is connected directly to the box, the
greatest gain antenna would be 13 dBi. Now you have to account for cable
loss. Cheap coax is high loss, low loss coax is expensive. The coax specs
will give a loss per foot, or meter.

If you axe the amp and go with the 15 db omni, and can manage only 2+ dB of
coax loss, you'll be at max. This can be done by mounting the device in a
nema box on the mast and using the PoE. I can only assume that you were
looking at the one titled: Long Range 802.11b Multi-Client Bridge & POE
Inj.

Almost always better off not using an amp. Why add cost, another point of
failure, and more complexity if you can get the same result's with a more
simple approach.

Also, while it's true that directional antenna's do focus the RF energy,
there is still side lobes that vary from design to design. These lobes can
be used to make successful connection's also as long as the system is
planned that each subscriber units operates at similar power levels.

Of couse, I was in at an ISP that had all type's of antenna's & coax's
available to use to mix and match as necessary, so that made it quite a bit
easier.......

> I have to repeat myself 1 million times everytime I post........ I
> know 2 directional antennas would be more than enough.... for a point

Well, it wasn't clear to me, you only mentioned two locations!

> to point. But this is NOT a point to point connection. This is a point
> to MULTIPOINT connection....like I said earlier. I MUST (1000%
> certainty) have a omni antenna on one end.

Why? If you have say 3 sites, use two access points in the middle site
and use two DIRECTIONAL antennas, one pointing to each of the remote
sites.

How many other sites are there?

David.

> Basically the only advice here is to change the multipoint design to a
> collection of point-to-point
> connections. It is very likely that you don't want to hear that, but please
> remember that multipoint
> is equivalent to a a single point of failure. Not a good design, but YMMV,

Quite, that's two of us saying the same thing so it must be true!

David.

1rst problem is it looks like you will be using conventional, 802.11 for
a multi-point system and you are going to get burnt by Hidden Node...
Although if done correctly, all child sites will hear the parent the
children will
not hear eachother, and since 802.11 uses CSMA, they will talk at the same
time..
CSMA works by a client listening, and if clear it talks.. if it hears
another system talking,
the client backs off for longer and longer periods of time.. i.e.
remember back in the
Ethernet HUB days "collisions" This is how 802.11 works.. so by
amplifiing the
BSU and putting the SU's with directional antennae, the SU's will not
hear eachother
so when they all talk at the same time, from the perspective of the
parent unit, the signals
will interfere with eachother and cancel eachother out...

Amplified systems and highly directional antennae are to be used in 2
configurations..
1) a point-to-point environment (reason why so many responses were
confused in your post)
2) multi-point system not 802.11... system with Polling... or clocking..
i.e.
polling like karlnet, Orinoco OR systems, and even the new crappy
MP11 by Proxim
clocking systems.. like the Proxim/WMUX Tsunami Multi-Point etc
etc which use
a GPS timed TDD system.

Legalities: (your true question)
The max EIGRP (effective power off the antenna) is truly 36dbm, but to
produce this
you have to play the db-1 rule to the output power of the radio as you
keep increasing the
antenna gain by 3dbi (double the effective power) Legally, you can't
just take any system
and do this... unless you want to certify your system radio, cable,
antenna etc with the FCC.
There are many already certified systems out there that you can use...
i.e. if you use the karlnet or Orinoco OR systems, you can put them
together with
either a YDI (very noisy), or a Hyperlink AMP with a certain set of
antennae and they
are already certified solutions. These AMP's are available as inline
remote at to be inserted
right at the antenna side of the feed line with inline power.. that way
it does not matter
how much feed line you use... this is important so not to have to
recertify a solution with a
different cable length.



Good luck!
"Kingz#1" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed) om...
> I am trying to create a multi-point wireless network. The main server
> will be 10km away. I do have LOS. This sight will be having a
> OMNI-DIRECTIONAL antenna about 80ft above the ground (to clear and
> obstuctions). Once of the recieving ends (which is 10km away) will be
> using a 24dBi parabolic Andrew antenna to try and link to the
> OMNI-DIRECTIONAL antenna. Here is our delema.... We first considered
> using a 15.4dBi omni 70inch antenna (from fab-corp.com) with a 1w
> outdoor amp linked to a 200mw Long-Range 802.11b router. After finding
> out that this was ILLEGAL.... (I'm assuming that it is harmful to ones
> health). I would like to ask the experts in this group what is the
> MOST powerful antenna I can use without breaking the law or causing
> any kind of health concerns to prelonged exposure.
>
> BTW: Here is some more info on the setup.
> Both routers are the same (200mw Long Range 802.11b routers from
> fab-corp.com)
> 24 dBi Andrew parabolic antenna (for the recieving end)
> both routers will be using 1ft low loss cable from antenna to router
> Also... from what I've read in this group... a 6dBi omni looks like
> the maximum legal limit for this amp. So my question is.... would the
> 6dBi omni with the 1w amp be better than the 15.4dBi omni without the
> amp???? If there is any better combo... please let me know.
>
>
> Thanks!
>

"Fresnel Fadermargini" <(E-Mail Removed)> wrote in message
news:z7sDc.2754$(E-Mail Removed) ...
> 1rst problem is it looks like you will be using conventional, 802.11 for
> a multi-point system and you are going to get burnt by Hidden Node...
> Although if done correctly, all child sites will hear the parent the
> children will
> not hear eachother, and since 802.11 uses CSMA, they will talk at the
same
> time..
> CSMA works by a client listening, and if clear it talks.. if it hears
> another system talking,
> the client backs off for longer and longer periods of time.. i.e.
> remember back in the
> Ethernet HUB days "collisions" This is how 802.11 works..

Wired Ethernet uses CSMA/CD (Carrier Sense, Multiple Access with Collision
DETECTION) and works as you described. 802.11 used CSMA/CA (CSMA with
Collision AVOIDANCE) and doesn't suffer from collisions nearly as often as
wired Ethernet.

Ron Bandes, CCNP, CTT+, etc.