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I just watched this 27 minute video on a very intense predictive site survey tool. I found it very interesting!

http://www.connect802.com/images/demo_clips/extended_video.htm

Interesting video. Thanks for the post. At around 15:00 in the video, it in my opinion not correct. It's not logical that the signal would be weaker directly below the dipole than further away -- even though the there is a known null in the dipole below it, and that is because proximity is even more of a factor than that null is (inverse square law in full effect here). No way your right under a dipole and its already down to -75.

Well it may be down 30db from max and if the dipole is mounted high up, the free space path loss may account for the rest of the attenuation. Not impossible. How high up was the antenna ?

I think in the video he was saying around 30 feet up. I don't know about you, but if there was an AP right above me only 30 feet away would be still hella strong. OK -- I'll give it a possiblity -- I guess. Another thing though to consider is he provides different scenerios where reflections of the signal are involved but not for this null scenerio in the dipole example. I guess just like they always say, nothing beats a real active site survey. I guess i'm in a nitpicky mood today -- its a very good video on showing the details of predictive site survey software.

The thing is, is the video right? If you mount an omni antenna 30 feet in the air outside on a light pole your RSSI directly below will be real low and increase until you walk far enough to enter the main lobe of the antenna. You can see that at least outdoors for the most part you can use predictive tools and at the end of the day be off by 2-3dB. What about a poor man?s 180? directional, a couple of omni?s mounted on a metal wall; can your software show me that; I don?t think so!
Now we?re talking about a warehouse right; so there is a ceiling where the AP is and its usually metal, the antennas are mounted within 2 feet of the ceiling, so now take the ?e? plane of the antenna, 180? from the ceiling and you now have excellent coverage right below the AP. Not all buildings have metal roofs, but most due, and no software out their models this. I?ve been involved with major vendors and their customers where predictive surveys were used and seen these major vendors loose big accounts based on this tripe; it?s so easy and much cheaper than a real survey. This also opens another can of worms regarding use of omni?s in a warehouse environment in the 1st place in that if you use them you have to use static radio settings as any type of controller based radio management is usually going to lower the radio power to account for the fact that every AP can see every other AP.

Excellent video on using Moto?s wireless valley software or whatever they want to call it.

I think Daniel hit the nail on the head....the predictive is a guideline . A site survey comes highly recomended.