I remember that article and I was going to do something similar on a wide faced tower that I was trying to get space on. It was a CATV head-end tower that was full of log periodic antennas, the only available height was from 125 feet to the bottom. I almost got the project started when the cable company got bought out and I lost all my contacts with the owner.
Anyway, if I had access to a water tank and had space available around the tank, I would mount 3 antennas equally spaced around the tank. If the antennas were shielded from each other by the water tank, I would probably try omni-directional antennas to keep it simple. I would then use a 3-way power splitter to combine the 3 antennas and just deal with the 6dB hit in signal for the ability to have omni-directional coverage. You can make up for the 6dB in the transmit path by raising the power output, but there isn't much you can do on the receive side except keep the receiver running a well as possible. These splitters are available, see: http://www.rfhamdesign.com/products/powersplitters/3waysplitter/index.html for an example of what I am talking about. Similar design units are available from a company in the Northeast, but I don't remember the name or location. One of the carriers does something similar. They put panel antennas on each of the 3 faces, then combine them into one omni-directional antenna system. It does work. I know of several water tank installations that are just like this. Joe At 03:00 PM 1/27/2007 -0600, you wrote: >This idea was in a ham magazine years ago, to solve a similar problem. It >was on a very large tower, with a large face. This particular application >used three sets of phased beams (two at each leg, fired tangentially to >the tower). You have to start out with a bunch of gain at each leg, not >just a dB224 or such. He used 2 five or so element beams on each leg. He >fed them with a three way power divider made out of copper pipe to get the >proper impedances. I wish I knew where the article was. I am thinking it >was not in QST but maybe one of the ham technical mags that is still no >longer around. I would search Google just in case a similar application is >documented. He said it worked OK and gave him a somewhat circular pattern, >albeit no more than 3-4 dB. > >Now that I think about it, with all the wireless stuff (cell antennas) >that I have seen mounted around a water tower single legs (the modern >towers), on buildings at each face, etc. , I bet there is info out there >that you can tailor for your needs using the phased antenna approach. > >Roger W5RD
