Its relevent to disclose the radio OS type using. (You stated using a R5H a Mikrotik card, but weren't clear if using Mikrotik OS). The symptom you are explaining sounds similar to how some of my Mikrotik OS units had responsed to noise. Basically they kept dropping speed until they disconnected. It was like watching a clock tick down to zero, and repeat. I had this problem recently with 900Mhz and MIkrotik, and the problem was curred as soon as I switch to a different brand product. I'm suspect, but not verified, nor conclusive, that it could be a Mikrotik driver issue. The point I'm making is that you are likely getting some sort of noise or multi-path (self noise), but the overall problem may not be the noise/multi-path but instead the inabilty of your product to adequately deal with that noise/multipath RF conditions.
The easiest place to do a science project probably isn't between two towers seperated by a 20 mile body of water, but it would make for a very interesting and meaningful science project. Sure a Mimo card w/ Dual Pol (for single stream) or Space Diversity would likely help deal with Multipath. But what I wonder is whether the same bad results are replicated with other single channel products of similar spec. It would be interesting to put up a Tlink-45, get results of it's noise survey scan, and see if it overcomes the problem. Or even try a StarOS box. Its also relevent to understand how much of the issue is canceled RF, and how much is side effects of 802.11 CDMA? I'm wondering if a TDD system w/ good ARQ better handles it. My point here is in an ideal world a radio should never have the characteristic to start at 6mb and slowly go to Zero. Instead it should stay at 6mbps, and just have a very high error count. Even if it has 50% packet loss it should stay associated, and with a TDD system w/ARQ it likely would.. Also note, if Using Mikrotik, they now support Atheros's threshold feature, to mask out weak signals, this can help reduce multipath signal. (although use cutiously as there can be significant fade of water with Fog/Clouds/evaporation/Solar and such.) Obviously if you switched to a TDD MIMO system, you'd optimize your chance for success, but you would not be able to learn what factor most helped the improvement. Tom DeReggi RapidDSL & Wireless, Inc IntAirNet- Fixed Wireless Broadband ----- Original Message ----- From: "Jeremy Parr" <jeremyp...@gmail.com> To: "WISPA General List" <wireless@wispa.org> Sent: Wednesday, October 28, 2009 9:20 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/ -------------------------------------------------------------------------------- Internal Virus Database is out-of-date. Checked by AVG. Version: 7.5.560 / Virus Database: 270.12.26/2116 - Release Date: 5/15/2009 6:16 AM -------------------------------------------------------------------------------- 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/
