When a 224 antenna is mounted on a leg of a 25G, 45G, 55G towers, the patterns are close to what DB had predicted as allowances are made for the distance off of the leg of the tower. EG: 1/4, 1/2, wavelength, etc. On large face towers anything is possible. As an example I mounted a DB 224 on the face of a Forestry Look Tower per a DB Engineers instructions. There were deep nulls in the pattern. One nul at 5 miles from the tower (You could see the antenna), the repeater would not key up with a 100 watt mobile. Large towers and water towers need to be checked on site for coverage patterns. (We mounted this antenna in Feb. 1966)
Good luck Fred W5VAY _____ From: Repeater-Builder@yahoogroups.com [mailto:repeater-buil...@yahoogroups.com] On Behalf Of Jim Brown Sent: Wednesday, July 01, 2009 5:47 PM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] DB-224 patterns on side of tower. Back when we had to submit an antenna pattern in order to get a repeater license for the ham bands, I mounted four elements of a DB-224 directly on one leg of a Rhon 25 tower and mounted the two tower sections on an antenna test pedestal and ran the pattern. With the antenna sections directly in line and pointed away from the tower, we had 9 dB gain in the favored direction, 6 dB gain at plus and minus 90 deg, and 3 dB gain off the back side of the tower. The plot was perfectly round with the 3 dB offset for the center point of the plot. 73 - Jim W5ZIT --- On Tue, 6/30/09, tahrens301 <tahr...@swtexas.net> wrote: From: tahrens301 <tahr...@swtexas.net> Subject: [Repeater-Builder] DB-224 patterns on side of tower. To: Repeater-Builder@yahoogroups.com Date: Tuesday, June 30, 2009, 2:35 PM Hi Folks, We are putting up the DB-224 on the side of the tower, which is one of those large 3 legged towers. (like you see at microwave & telephone sites). I have the DB-products data sheet on the 224, and it has some plots for side mounting on the tower. The plot in question is the 224E (all in line, pointed away from the tower). According to DBprod, it would give the appropriate pattern for our desired area. However, one of the old salts here (who has final say-so) says that you really have to put some left and right angulation on the elements to get that pattern. I guess the real question is how positioning on the side of the large tower affects the pattern - if the elements are directly perpendicular to the tower leg, versus having some rotation on the leg. I'm thinking that we will probably just have to experiment with what we get per old-salt's method & see how it works. Anybody have any other ideas? Thanks, Tim W5FN
