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9' Glenn Martin tower on my 2nd-story roof which puts the C3e about 36' off the ground. Everything is working as designed with the exception of an interesting problem. When the yagi is pointed East my VSWR goes up to 3:1 on 20 meters from it's normally flat 1:1 VSWR. When I swing the beam away from the Easterly directionn the VSWR drops to its "normal" low state, picks up somewhat when pointed West, but drops again when pointed South. For a visual, see my website www.k6sdw.org That's me next to the tower and that BIG amount of metal East of the tower is our heat-pump. Notice the heat-pump is East of the tower and the C3e hangs over it when pointed East, South-East. And again, the butt of the beam hangs over it when pointed West or North-West. So, I'm guessing that the large amount of metal East of the tower is coupling to the C3 and causing the high VSWR. Now, using an antenna tuner easily brings down the SWR, but what is happening to my radiation pattern -- I have no idea?! And of course, East and North-East are my two most important directions...it figures! HI! Now the question for the antenna wizards: Short of removing the 5-element 6mtr yagi at the top and pushing the Force12 C3e up another 5' is there a way of electrically "hiding" the heat-pump from the yagi when on 20 meters? The other bands are not being coupled to this mass of metal so they don't present a problem. Thanks much........73........k6sdw -------------------------------------------- Force12Talk mailing list provided as a service by Force 12 Antennas, Inc. Force 12 Web site: http://www.qth.com/force12 Submissions: send to Force12Talk@qth.com To unsubscribe: send a blank e-mail to Force12Talk-leave@qth.com Force12Talk Message Archive: http://www.qth.com/force12/list/force12talk For problems with the list, contact n4zr@qth.com |
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