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Ron's Web Site
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Date: 5-30-2010
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Number of Hours: 3.00
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Manual Reference:
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Brief Description: Marker Beacon Antenna
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I rigged up a temporary cardboard wingtip and fabricated a Bob Archer-style marker beacon antenna using RG-400 cable. Bob Archer recommends a 40 inch section of exposed ( insulation only) conductor, but I wanted to optimize the antenna within reason so as to hopefully only do this once. Accordingly, I set a SWR meter initially to 75 Mhz, and then adjusted the frequency until minimal SWR was found. I multiplied the ratio of the low SWR frequency divided by 75 MHz times the initial antenna length, and found that 27.75 inches was a more optimum length than 40 inches on the Bearhawk. Further optimization would require glassing the antenna and then rechecking, then probably trimming some more with a dremel tool as fiberglass effects the SWR, but that would have required considerable time and effort, and I figure (and hope) this is close enough. I then temporarily fixed the antenna in place using tape, spot welded it with 5 minute epoxy, and then glassed it in place with two-ply and epoxy resin. I then left enough cable for a service loop, and placed a BNC connector which will mate up with the outboard rib BNC connector.
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Cardboard wingtip and initial antenna in place.
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SWR meter.
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Marker beacon antenna epoxied in place.
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