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In many of our designs we use a hairpin matching device (coil) across the feed point. This coil is used to introduce enough "L" to increase the impedance to a value of 50 ohms so as to match 50 ohm coaxial cable. We use this matching technique on most all our 30 through 160 meter designs and on some of our 20 through 10 meter designs also. The hairpin, or coil, has little if anything to do with establishing the resonance of the antenna. The effect on resonance is greater at 160 meters, but even there the hairpin has minimal effect on the resonance (as indicated by a dip in VSWR.) Adjustment of the coil, by changing the spacing between turns, will change the feedpoint impedance certainly, however, adjustment will not change resonance significantly. If you need to move the resonance of a driven element, don't plan on using the hairpin coil to accomplish that objective. 73 Natan W6XR Force 12 East Ithaca, NY FN12sk force12@qth.com -------------------------------------------- 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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