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Read Hank's posting and wanted to add my 2 cents worth. My experience on 80 and 40 meters agrees 100% with Hank's observations. Living in the PNW, I am blessed with any number of really tall Douglas Fir antenna masts for my antenna projects. Over the last few years, I have been conducting on the air A vs. B comparisons of horizontal dipoles and some inverted V's in various orientations on both bands for DX. My observations are that a horizontal dipole does show a definite null off the end of the wire, and that the inverted V shows relatively little but not "no" directivity. I have come to the same conclusion, "higher is better" for DX, and that a high wire in the tops of a trees is more effective than a rotatable dipole on a less high tower. A single good and high inverted V is a match for DX compared to a rotatable dipole at typical tower heights, e.g. 60', on the low bands. The only exception could be if the tower installation is better sited and away from buildings or power lines. In that case, other near field factors could come into play and tip the balance in favor of the tower mounted rotated dipole. Some reduction in local noise pickup on reception is possible with a rotatable dipole. Rotatable dipoles on a typical single tower installation adds the possibility of interference with the other antennas, especially a 15 meter yagi, and does add additional wind load and a measurable reduction in the safety of the entire installation. Rotatable dipoles do have the advantage of "bragging rights" and are impressive to look at. Best regards, John Petrich, W7FU ----- Original Message ----- From: "Hank Phillips" <aa4hp@titustek.com> To: <hafner_ko6ic@yahoo.com>; <Force12Talk@qth.com> Sent: Sunday, October 06, 2002 9:33 AM Subject: [Force 12 Talk] 40 Meter Dipoles and DXing > Jack, > > Just a quick observation on 40 meter DXing. I am using an inverted vee at > about 60 feet and it doesn't display any really detectable > directionality. For a while I had a second vee at 45 feet, oriented 90 > degrees to the taller one, but I recut it for 30 meters after testing > didn't reveal any benefit from the second antenna. I doubt that even at 60 > feet the vee has much of a low angle component to it, but it may not > matter. If you will concentrate on the sunrise and sunset periods to chase > low band DX, the arriving wave angles are rather high. Running a KW into > this antenna system snagged 200 countries on CW in just in the last two > winter seasons alone. This may get easier as we come down off of this > sunspot peak, and more DX gets chased down to the lower frequencies. > > I think before I put up a rotable dipole for 40 at a low height, > particularly if it is something like a shorty forty, I would use a full > sized wire antenna. Depending on your local tree type and count, you might > be able to get it up a bit higher than something with a rotator under it. > > No matter what you decide, have fun with it. > > Very 73, > > Hank > AA4HP > > > > > -------------------------------------------- > 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 > > -------------------------------------------- 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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