Positioning antennas for diversity

[dc2005]

This topic may have been discussed before, so apologize in advance if I've missed it. In summary, we have some fairly long links, up to 10 - 15 miles, over the open sea that exhibit deep fading cycles in line with tidal changes e.g. one 12 mile link on 2.4GHz peaks out at an SNR of about 27dB at low tide and then fades down to an average of about 15dB at high tide. I realize that this type of propagation behavior is expected over water, my question is in relation to the use of diversity to help alleviate the effects of fading like this. I've been told that situating one end of the link higher up, or further inland, than the other side can help. My question is in relation to the use of diversity to help compensate for such fading. I was wondering if anyone could give advice on how to position antennas etc to maximise the benefits of diversity? Also, has anyone out there experimented with different polarisation patterns on these types of links?

Thanks for any feedback.

[simcor23]

When I ran a wisp in the mountains of B.C. We had a heck of a time shooting across the fairly lage lake we were on, no tide but lots of fade and wacky stuff happening. Now I don't know how many people have tried this but it was suggested to me by a guy from another wireless company in the area who was dealing with the same issues as us. We crossed polarized our 24 dbi grids. ie: One grid was horizontal and the other vertical and it solved the problem. I dont know if that is supposed to work theoretically but it did. Anyone else tried this before?

[go.fast]

I had a shot across a lake that we were having issues with.

The ap and the client weren't much more than 50' above water level.

Changed out the link to a set of wars running 5 and 10MHz channel width and the link is now stable and fast.

George

[dc2005]

Did a bit more research and I came across this URL which seems very relevant:

http://www.wlanantennas.com/wlan_faq_radioprop.htm

Looks like diversity will help but the optimum vertical separation required may require some experimentation in each case.