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80-10 Helical tapped mobile whip
On Feb 21, 5:08 pm, Cecil Moore wrote:
Eric wrote: But then, winding a helical for 80M is not going to be fun, either. If memory serves, I think you need a half wavelength of wire wrapped around a pole. Seems to me the wind loading is going to be a severe problem. Let's say it is 8 feet long. At 2 turns per inch, it would need to be about 3 inches in diameter. That's about 200+ square inches of wind loading. It will probably require a guyed fiberglass pipe as a coil form. I calculate about 150 feet of wire is needed for the above design. -- 73, Cecil http://www.w5dxp.com What he wants to build is what outbacker sells. Has taps with banana plugs to change bands. I don't know of any plans to build one. It wouldn't be that big a deal though. A bit tedious finding the tap points, but it can be done. You could calculate the various points to get in the ballpark, and then clip to, or probe the wires to fine tune the tap. I'd probably start on the lowest band and go up to the highest freq it will tune with whatever length stinger whip it is using. My plastic bug catchers are about the same thing, but using a single lumped coil, vs the thinner helical winding. It's best to concentrate the windings at the top of the glass whip to improve current distribution. Using an even space winding along the whole stick is not quite as good in most cases. MK |
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