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I thought I'd contribute my somewhat hasty comparison of 40m inverted Vs and a rotary dipole. I recently built a Force 12 Mag140N rotary dipole for my part-time QTH, and installed it right above the old HyGain 204BA at 79'. The tower is on a hill that rises sharply to between 300' and 400' over the surrounding terrain (see photo of QTH and tower - without 140N - at qrz.com). I had previously been using two wire dipoles, mounted more or less as inverted Vs, one broadside toward Europe at 60' and the other toward the Far East at 76'. The advantage of each in the intended direction was significant, typically one to two S units, and undoubtedly would have been greater had they been straight dipoles. (I suspect the difference would have been considerably less if the tower had been on flat terrain, as 76' is not electrically high at 40m.) I was unable - not surprisingly - to compare the 140N with the higher inverted V because they thoroughly hosed each other up. With that one out of the way, I compared the 140N to the other one at 60' (this one actually had one leg almost straight out, the other angling down at about 40 degrees). (No doubt there was still some interaction, but it was not noticable as a significant shift in swr.) Toward Europe, signal levels were indistinguishable between the two antennas. (I should mention that simulation with TA shows several db advantage toward Europe at the lower height, given the shape of this particular hill.) In other directions, the advantage gained by rotating the 140N to the optimal position was quite significant. So far, I have used the 140N very little, but signal reports and performance in several pileups have been extremely encouraging. Let's see if it survives a winter on the hill. I had to rebuild the 204BA with fat elements to prevent the annual spring walk through the woods to collect pieces. 73, Al K8AL -------------------------------------------- Force12Talk mailing list provided as a service by Force 12 Antennas, Inc. Force12 Web Site: http://www.force12inc.com To Submit Message to the List: Force12Talk@qth.com To unsubscribe and view the Message Archive: see http://qth.com/force12/list For problems with the list: contact n4zr@qth.com |
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