Marine AM system

Ken Norris · 2010-01-07T05:50:29Z

Howdy, We've talked before about this, and I realize the experimental nature of my endeavors, but I'd like some clarification on a few issues. Howdy, We've talked before about this, and I realize the experimental nature of my endeavors, but I'd like some clarification on a few issues. 1) My boat is not large, about 28 ft., weighing in at about 6 tons. It's wood, last of the Owens wood lapstrake and plywood hulls. 2) The cabin roof is where I want to mount the antenna system. It's about 6 vertical ft. from the waterline. 3) The boat has two separate power systems: (a) Batteries, 2 banks -- 12 vdc on board, negative ground bonded to the through-hull at the transom which is under the water line (zinc block). There is a power panel inside the cabin mounted in the starboard bulkhead by the cabin entry ladder. (b) Shore Power -- 110 vac, normal neutral ground, two 20 amp breaker boxes in the head area of the cabin. The only place they come together is the Marine Charging System, which isolates them. 4) I want to propagate signal up into town as far as I can get. There are some cliffs, buildings, and parking lots above my portion of the marina. 5) I'd like to power the system from the battery side, the same as the LORAN and VHF, but the PS' for the computer supplying the audio and also the TX are 110 vac adapters. The computer one outputs 24.5 vdc/2.65 a. The TX one outputs 15 vdc/.8 a. Both are regulated. The questions go like this: A) What would happen if I use a 12 vdc to 110 vac inverter to plug the current PS' into? I have no idea how those things handle grounding. B) My best idea is a compromise: A rooftop style tripod with a 3' steel pipe mast. The pipe clamped by the tripod, but also mounted to a flange on the cabin roof and to a flange on the bottom of the loading coil. The TX feed line a shielded cable inside the pipe, not visible outside. The TX mounted to the underside, i.e., the cabin ceiling out of the weather ... also very close to the 12 vdc Power Panel (for ground). I don't see how this could radiate anything significant ... certainly no more than audio cables on some units. How legal would it be (hey, TH transmitters can use TX line cables)? The antenna in this case, instead of the old Shakespeare whip, would be a sort of cross between the SSTRAN-style antenna and the Manteca Magnum ... tunable. Except for polishing and preserving the copper, this is ready to go. I would guy the top portion with 4000 lb. poly lines. Overall, it should be a very stable, clean, and good-looking installation, but a lot of work. I can loosen one of the tripod legs and the pipe from the flange to lay it down by the other two leg hinges in case of a really heavy storm. C) ...But will it work?

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Anonymous

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While AM is Groundwave.
At such low powers buildings can significantly mess with the signal.
I recall from my Days in Seis Lagos that The Signal traveled pretty good over water and covered a good chunk of the small neighbor hood with just the wire antenna on the 2nd story balcony. I also remember that if I turned the corner by this one house the signal dissipated practically completely because the antenna didn't reach over it, and the signal didn't return untill i passed the house.

Posted : 11/01/2010 3:11 pm

Anonymous

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Which Mexican restaurant?

Posted : 11/01/2010 6:25 pm

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