Home - Techniek - Electronica - Radiotechniek - Radio amateur bladen - QST - The balloon antenna rides again!
More practical dope on gas-filled skyhooks.
Here is good news for the ham with the condensed backyard but expanded antenna ideas. Hydrogen and helium gases are not required! Further, they are both too expensive and too cumbersome for the average enthusiast to use in putting up "Kytoons,"(1) or just plain round balloons.
In spite of its low pressure, ordinary house gas brought out of the cellar with the garden hose will inflate any prewar-style meteorological balloon to bursting. Coal gas averages a specific gravity of 0.5. This means that a given balloon must be inflated about 20 per cent greater in diameter by coal gas to equal the lift of hydrogen. The surface of a balloon increases as the square of the diameter while the gas volume increases by the cube of the diameter. Hence, a natural gas of only 0.75 specific gravity could still be used for balloons with some compromise.
During the summer of 1941 I set out three vertical full-wave antennas on 160 meters. Somehow there is an immense thrill to letting a balloon up eighteen times as high as the house. It provokes a peculiar type of elation much like the first overseas contact. In each case the support was a D & A Co. balloon filled with house gas through the garden hose. The distinctive odor of house gas is lost through latex, so that the sense of smell cannot be used as a safety check on releasing the gas at disassembly times.
The first two balloons were only about 3 feet in diameter, and supported just one strand of No. 26 wire in the safety of the night. Because of the nearby airport I lighted the third by two auto bulbs internally mounted through the neck gas seal and fed by two enameled wires. The wires were fed from the ground through r.f. chokes.
The third balloon was about eleven feet in diameter. It took 3 hours to inflate it with a half-million cubic inches of gas at a cost of about 85 cents. Two hundred feet of light 3-ply house twine were used in a triangular-shaped balloon net to support the wire, because the neck of the balloon was listed by the manufacturer to be safe only up to 5 pounds lift. A car battery was used for an anchor, since it was soon apparent to me that our muscles are not built for holding down the ten pounds lift which a spring scale indicated. I experienced some difficulty in getting the top of the balloon to expand under the pressure it exerted on the net. Perhaps talcum on the string would have helped. The extra stretching on the bottom might have shorted its life to eight hours in the air. With even expansion it was not rated for over 9 feet in diameter, but I went the whole hog. This was in daylight.
The effect was astounding. Crowds swarmed the neighborhood. No parking places were left on either side of the road. Mother almost fainted when she saw little children running across the road while Sunday drivers drove their cars with their heads out of the windows to look at the balloon. One carload drove in from fifteen miles away, having determined to track down this new planetoid.
Transmission and reception were equally spectacular. To start with, the HQ-120X would no longer take care of the two local broadcast stations - 450 kc. apart, i.f. of receiver 455 kc. - without wavetraps. Whole states usually unheard in the daytime were heard and worked on 160 meters, with good reports both ways. Thirty watts of phone was used. It seemed to be a little better in all directions than my horizontal full wave was in its very best direction. The full-wave vertical seems to be a great low-frequency antenna.
George Bonadio, EX-W8OMM.