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2.4gHz WLAN Segment through a bit of foliage? |
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Written by Deven07
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Sunday, 20 August 2006 |
"Hi, I'm looking to install a WLAN segment about 3/4 mile across a lake, with a very small strip of foliage at each side posing some interferance concerns. This connection would be installed in hopes of creating a very small home brew WISP on the side of the lake with no connectivity.
On each side of the 3/4 mile middle, there is some treeline probably 10 yards wide, through the tops of some sparsly foliated poplars on one side, maples on the other, again probably 10 to 20 yards wide. I can see through the tree(s) pretty well to the other side, but there definately is no clear window without any foliage present. Inside these short treelines is obviously no obstruction whatsoever, being over the lake. Each antenna would probably be 20 - 40 feet high. Do you think this small amount of tree interference is going to make this connection tough to establish? I've seen some 2.4gHz applications blow through some trees before, but never have had hands on on a project that tried it. I was thinking of using 14db panel antennas with linksys WAP54G's. Any help you can give would be much appreciated!"
slipstream1:
Your problem would be attenuation instead of interference. As for the main question, 2.4 Ghz might be able to do this on this short scale, but there is only one way to know for sure, buy some inexpensive 2.4 Ghz gear and try it.
superdog1:
I would also try and use 45 degree polarity instead of vertical or horizontal, as some say it seems to work a little better thru trees?. I think I would be more worried about issues from the lake then the trees?, as water can create some pretty crazy multipathing issues, especially when the lake is choppy, as each one of those little waves creates a surface to reflect RF, causing not only Your intended signal, but a bunch of reflected ones also. To give You a simple example of this, have You ever noticed when driving in Your car and You stop at the red light, Your FM radio starts acting up?, and then after You move forward a foot or two, it starts to come in clear again> This happens because the intended signal and a reflected one hit the antenna or radio at the same time, causing them to cancel each other out, and when You move forward, You move out of the reflected signal, and the radio starts to come in clear again.
Newer radios use this chaos to their advantage(OFDM), but OFDM is only available in 802.11G and 802.11A radios, and 802.11b radios just puke and die because their receivers can not handle the mess.
lutful:
You will be fine with 250mW TX power with 14dBi antenna, or 100mW TX power with 19dBi antenna.
I say this because I have longer links where I can barely see a light on the other side at night after all the leaves fall from the trees.
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