It's probably ducting. Where the conditions in the AIR literally bend the signal over or under your receive antennas.
You'll likely have to put in a system designed with something called "antenna diversity". Basically two antennas for each link. One 10 to 20' higher than the other one. Then the radio will listen to the two of them and switch to the one with the greater signal levels for it's data flow. I always wanted to try this using a splitter placed EXACTLY in the middle of the two. But with wave lengths so small I don't think it's likely that I'd get it close enough without a lot of blind luck (get it wrong and you create multipath inside the cables). This'll be a tough one. marlon ----- Original Message ----- From: "Jeremy Parr" <jeremyp...@gmail.com> To: "WISPA General List" <wireless@wispa.org> Sent: Wednesday, October 28, 2009 6:20 AM Subject: [WISPA] Long 5Ghz link over water >I have a 23 mile link completely over water that I cannot get stable. > One end is approx 200ft AGL, 220ft ASL, the other end is 50' AGL, 90' > ASL. Antennas are V-Pol 29dbi grids, radios are R5H cards. I have > tried the link at both 5.2, and 5.8, but it still fluctuates > dramatically. When the antennas were installed and configured for a > 5Mhz channel, I was able to aim them to -55, but still they go down > during parts of the day. I have a second antenna hung on the 200ft > end, at about 185', connected to a second R5H set up for H-Pol which I > am going to light up as soon as I get the other end mounted H-Pol. Any > other suggestions for getting this stable? I also notice some > strangeness when doing bandwidth tests. I can get a steady 8mbps > downstream from the 200ft end to the 50' end, but from the 50' end to > the 200ft end, the transfer starts at about 6mbps, then slowly drops > down to 0, and the client radio (the 50' end) drops. My assumption is > multipath reflections off of the water at the lower end, but I cannot > be sure. The water is tidal, with as much as a 3' change from low to > high, and is connected to the ocean, so there can be considerable chop > and wave action on the surface. > -------------------------------------------------------------------------------- > > > -------------------------------------------------------------------------------- > WISPA Wants You! Join today! > http://signup.wispa.org/ > -------------------------------------------------------------------------------- > > WISPA Wireless List: wireless@wispa.org > > Subscribe/Unsubscribe: > http://lists.wispa.org/mailman/listinfo/wireless > > Archives: http://lists.wispa.org/pipermail/wireless/ -------------------------------------------------------------------------------- WISPA Wants You! Join today! http://signup.wispa.org/ -------------------------------------------------------------------------------- WISPA Wireless List: wireless@wispa.org Subscribe/Unsubscribe: http://lists.wispa.org/mailman/listinfo/wireless Archives: http://lists.wispa.org/pipermail/wireless/
