I will have to second the ducting analysis. 23 miles is a long way over a water path. You can use space diversity by using a pair of antennas/radios at the same frequency, with 20 foot or more of vertical separation. You could try frequency diversity also. Many times a duct will affect frequencies differently at times during the event. You do know grids don't have a very clean pattern. A dish will focus more of the energy where you want it. If you are limited to space on the tower(s), a dual band feed dish might be your solution. You could run 2.4 and 5.8 at the same time and have software "vote" for the best link at any moment.
In the past I built a 20 mile water path with space diversity using very expensive Nortel radios. This was in SW Fl, where ducting is common. The system would switch antennas several times in a month. These were OC3 radios at lower 6 GHz. The upper dishes were 10' and the lower were 6'. I think the separation was 20'. BTW, that was in 1999, and the link is still running. Mike At 08:20 AM 10/28/2009, you wrote: >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. > >Content-Type: image/png; name="graph_image.php.png" >Content-Disposition: attachment; filename="graph_image.php.png" >X-Attachment-Id: f_g1c41wi50 > > > >-------------------------------------------------------------------------------- >WISPA Wants You! Join today! >http://signup.wispa.org/ >-------------------------------------------------------------------------------- > >WISPA Wireless List: [email protected] > >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: [email protected] Subscribe/Unsubscribe: http://lists.wispa.org/mailman/listinfo/wireless Archives: http://lists.wispa.org/pipermail/wireless/
