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Goal:
* Minimum fuss 3-30MHz operation, mostly on 5-15MHz. * Will use step-dowm RF transformer between antenna and low impedance coax * May use autotuner on TX * Like the wirecage antennas still today seen on many a military vessel. Available on roof: - 25ft steel structure (like piramid base for power line) - about 100 feet space in one direction -...to abandoned flue chimney, 100ft away and 10 feet lower than base of steel structure - roof covered with alu plates on tar (could be all arc welded together, perhaps. THIS LOOKS PRETTY MUCH LIKE A SHIP TO ME cept its' 120ft aboveground. I want to build a wire cage monopole - sloping down from steel tower - using tower as counterpoise - feedpoint at top of sloper, via stepdown rf transfomrer, grounded to tower - coax cable lead, with rf choke coils and surge suppressors. Questions: - what kind of cage antenna? - how many wires? - what spreaders, how large? - ideal wire? Current plan config: - length 14 m = 2 x 4m straight sections, + 2 x 3m truncated cubes - spreaders at 3-7-11 m - 140 cm dia. spreaders, each made with two waterproofed bamboo triangles in "star of David" configuration; wire kept parallel at 70cm distance from each orther. - material: .8mm copperclad, abt. 90 m (270 ft) total. Any hints, like more/fewer parallel wires, broader / smaller spreaders, different materials, dirrerent antenna wire, RF downtransformer, whatever? Filippo |
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