Breezenet Pro-11

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.

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.

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.

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

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

opinions?

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ringram hath wroth:

It's Alvarion, formerly Breezcom.

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.

Do you have Fresnel Zone clearance?

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.

Well, can you do the calculations for me? I'm doing the recovery thing and am too lazy today. See:

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.

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.

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.

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

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.