[amsat-bb] Antenna question
kd0ar at sbcglobal.net
Sun Sep 21 04:22:30 PDT 2008
I built one of Kent Britain's "Cheap LEO Antennas" as a handheld antenna, and I have a question.
I built mine on a 3/4 inch ID PVC boom. works great!. Anyway, there are a good number of designs out there that use a folded dipole for the driven element, Kent's is of course "half" folded. However each of these folded elements I see, it is folded perpendicular to the plane of the antenna. (in otherwords, if the antenna lays flat on the floor, the element fold is vertical) I have a small 2 meter antenna that uses one and its perpendicular also. My question is, to simplify mounting to a small diameter insulated boom, could such an element be placed "laying down", so the element could be better supported by drilling 2 holes in the boom? In a normal folded element, balanced, I would assume the radiation center would be located at the center between the 2 parallel rods. The thoery that Kent uses for his states that the "j" portion of his, the J is the matching section, and the half wavelength rod, I would then assume to be the radiator.
I'm building this one to replace a "permanent" station antenna, which uses tee matches for the drivens. Kent's is easier to build, and would be easier to do if the element could be laid down on its side. Would like to get your thoughts on the thoery. I wouldnt think it would matter, as either way, its a dipole, and they all radiate 360 degrees around the element. Just trying to figure out why theyre all designed in the orientation that they are.
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