here is the way to do it, with yagis. I met one of the individuals involved in this effort on a trip to Quincy and also was able to purchase several of the Yagis that were made using the criteria that came out of this excellent work. http://www.repeater-builder.com/antenna/pdf/wr9aea-antenna-n9sn-hr09-79.pdf You can see that aiming the Yagis straight away from the tower gives a really poor radial fire pattern, compared to tangential placement. As I recall, he said they used the Harris Broadcast antenna testing field during "off hours" but if they had done it as a project the company would have charged a lot of $$ so much they could have never accomplished the work. Note that the antenna modeling was done at 955 MHz so it should be directly applicable to the present discussion. Personally, I would use several panels with combiners to cover one side or the other of a large tower at 900. To get a textbook perfect pattern requires a top mounted antenna. W6 MTF
--- In [email protected], "skipp025" <skipp...@...> wrote: > > > Actually it can be done and we've talked about it before. But > normally it is or was done with yagi antennas on larger face > towers. I probably still have a pdf copy of the original > magazine article I scanned some years back and made available > to various group members when that topic was first brought > up here. You might even check the Repeater Builder web site > to see if it made it up/over there. > > cheers, > skipp > > > "Gary Schafer" <gaschafer@> wrote: > > As far as phasing the antennas around the tower, it can't be done. Well it > > can but you will end up with more nulls and a worse pattern than you started > > with. > > > > The problem is that most signals will arrive at more than one antenna. > > Because they are different distances apart to the mobile there will be a > > time difference between the two. > > So you say ok, I will just make the phasing harness that same length as the > > antennas are apart. > > That would work great for one specific direction. But what happens when that > > mobile moves to a new azimuth location? Then there will not be the same > > distance to him between the two antennas as there was when you made the > > phasing harness. Now you have a new time difference between arriving signals > > but you have the same length phasing lines. The result is that the combined > > signals are no longer in phase so you have less gain. If the two signals > > fall out of phase then they will cancel. You have a big null in the pattern > > there. > > > > 73 > > Gary K4FMX > > > > > > > -----Original Message----- > > > From: [email protected] [mailto:Repeater- > > > [email protected]] On Behalf Of afa5tp > > > Sent: Wednesday, March 10, 2010 12:31 PM > > > To: [email protected] > > > Subject: [Repeater-Builder] Antenna Phasing Question > > > > > > Hello Folks > > > > > > I have three (3) Antel [BCD 80010] 806-900 mHz vertical antennae that I > > > would like to mount on the three legs of my tower for omni pattern (Rec. > > > only). Several questions come to mind. > > > > > > 1.) At the rated frequency, how many inches should the side arm place > > > the ant. from the tower? > > > > > > 2.)What would be the best way to phase the antennae? I have a Andrews > > > three port "Splitter", and will use "LDF4-50A for feedline. I would > > > suspect the length of the pigtail from each antenna to splitter is going > > > to be critical.......or not, for receive only? > > > > > > BTW......How good of an antenna is the "Antel" BCD 80010? > > > > > > Many thanks for any guidance and wisdom. > > > > > > Tim Hardy > > > W7TRH/AFA0TP > > > Vashon Is. Wa. > > > > > > > > > > > > ------------------------------------ > > > > > > > > > > > > Yahoo! Groups Links > > > > > > > > > > > >
