Re: Breezenet Pro-11

ringram <ringram.2vmn4d@no-mx.wirelessforums.org> hath wroth:

>I need to connect two buildings with a wireless link. I plan on using a
>Breezenet (now Alravion) Pro-11 access point at one end, and the
>Breezenet Pro-11 wireless bridge on the other end.

It's Alvarion, formerly Breezcom.

>Why these units? Because I have them, they have good specs, will suit
>my need, and aren't currently being used. They use frequency hopping
>spread spectrum.

Yep. You get to trash any DSSS wireless system along the line of
sight. FHSS takes up the whole band, so there's no clear channel.

>I plan on using Cisco a yagi 13.5dBi antenna at each end.
>
>The distance is 4.2 miles. I plan on mounting the antenna on a mast on
>a tripod on top of the roof of each building to clear the trees so that
>I will have line of sight.

Do you have Fresnel Zone clearance?
<http://www.terabeam.com/support/calculations/fresnel-zone.php>
At midpoint of your 4.2 mile link, you'll need to be clear at least 39
feet radius from the line of sight. Do you have that much clearance?
That includes clearance above the ground, so your antennas will need
to be at least 39 ft above ground level.

>The question is, will these be enough to cover that distance?

Well, can you do the calculations for me? I'm doing the recovery
thing and am too lazy today. See:
<http://wireless.wikia.com/wiki/Wi-Fi#Link_Calculations>
for link calcs. If you don't have tx power and rx sens data on the
Pro-11, I can dig them out (maybe). Aim for at least 10dB fade margin
(system operating margin).

Ah, foundit.
<http://www.winncom.com/moreinfo/item/AP-10D%20PRO.11/index.html>
speed sensitivity
Mbits/sec -dBm
3 -67
2 -75
1 -83
TX power also varies. I never could get the rated +20dBm. I would
give it +17dBm tx power.

>Obviously, higher gain antenna's will help, but with larger antenna's
>comes more wind loading.

That depends on whether you're dealing with icing. Most 24dBi wire
grid (barbeque grill) dish antennas have very little wind loading, as
long as you don't have to deal with ice loading.

>I would like to have the radio's mounted inside
>the building, but the attenuation on the coax may limit the signal, so I
>may have to make provisions to mount the radio in a weather proof box at
>or near the antenna.

Well, if you're going to do that, use a panel antenna against the side
of the building.

>opinions?

Yeah. If you're shooting across a city, with lots of other wireless
systems along the line of sight, you're going to have an big
interference problem. In addition, FHSS devices have lousy receive
sensitivity, so your range may be limited. Even at the maxium speed
of 3Mbit/sec sec, the best you can do is perhaps 1.5Mbits/sec thruput.

--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558