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Sail Magazine article on ham antenna?
Jon Gauthier wrote in
: Larry, that's what you keep a balloon and tank of helium for. Or a kite for those of us on the cheap! SHHHH!@ Don't be givin' away my Field Day secrets!.... Have you ever seen one of those blimp-shaped balloons with a car dealer ad on the side of it over the dealership way up high...even in the wind? Looks just like a little Goodyear blimp on a 3-point tether to a line to the ground. Well, I wondered how one of those would do for a 160M and 75M vertical, 1/4 wave or half wave (end fed with a tuner..no ground needed). So, When the dealer took the balloon down, I figured he'd store it for another promo at some future time. I asked him if I could borrow it the day after I noticed it was missing from his Chevy lot. "It's out in the dumpster and you can have it if the dumpster hasn't been dumped, yet." I rushed out back and did a little "dumpster diving" retrieving this invaluable piece of aircraft, its tether, and enough line to fly it at 2400 AGL! As the rented Helium tank had gone back to the ad company it all came from, I stopped by WalMart and bought a disposable helium balloon tank, actually 2 of them but I didn't need two. I replaced the "downhaul" line with some 1/16" braided dipole cable that I have on an old military portable dipole made for Army field HF stations. The "hot side" (there's no balun) was flown up vertically by the balloon. The shield side was laid out on the ground, 1/4 wavelength on 3900 Khz. We strung out the wire as the balloon lifted it all 64' up and clamped it off on the portable dipole's contact, the center of the portable dipole now tied to a big tent stake driven into the ground. No tuner was necessary as the feedpoint impedance was measured to be around 38 ohms with just one radial, not buried. Signal reports were amazing! The full-length 1/4 wave vertical performed like a broadcast tower. Bandwidth of such a thin wire was about 40Khz to the 1.5:1 SWR points but as the dipole reels were laying in the lawn, adjusting them to a different part of the band to get the SWR flat was real easy. This blimp-like balloon is MADE to fly in the wind. The 3-point hitch insures the balloon doesn't "tilt" as the wind pushes at it. When it tilts with wind pressure, the airfoil of it lifts harder and the 4 tailfins point it to windward, providing lift to keep it on top of its arc, not blown down to the ground. Works great! On 160 meters, tuned around 1.870 Mhz, bandwidth is about 25 Khz with 120' or so of wire aloft. The blimp has no trouble maintaining altitude of that much wire. There's plenty of lift that actually increases with wind pressure! I worked Arizona on 1855 Khz at midnight, 10 over S9 with 650 watts into it from my solid state Tentec Hercules II modified linear amp....around 120A at 13VDC from two T-16H deep cycles and a cheap charger. Makes top-banding possible on my small lot. This would work at sea if the damned boat didn't go up and down and back and forth...(c; It'd work great at anchor in a quiet harbor... |
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