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I'm a little stumped.
I'm sure I'm missing something obvious but I just can't see it. Built a 40m wire dipole, 33ft per side, symmetrical. Center mounted on an 18' pole. Ends of the legs drop about 2 ft to 16' above ground. Slack/dip in the wire legs is pretty minimal. The mechanical connections of my antenna allow me to get it pretty tight. Without any balun, running coax to the center feed point of the dipole, I get an impedance of around 6-7 ohms. Different lengths of coax, different pieces of coax, make no difference. All the coax pieces I've tried test ok for shorts and continuity. Two of the test coax pieces are brand new. Dipole legs aren't touching anything, including each other. Nearest piece of metal is at least a half wave away from the end of one leg. Mast is an aluminum tubing tripod in sections. The sections aren't particularly bonded, the section connectors are plastic/nylon. The telescopic sections of the tripod/mast are 4' long each. The mast has rubber feet on it's tripod legs, it is not bonded to earth. Same 6-7 ohms shows up on the MFJ meter whether the mast is at 10 ft or 18 ft. Same 6-7 ohms shows up whether I stand at the base of the mast with a 17' piece of coax attached, or if I add a 50 or 100 ft length of coax and stand virtually anywhere. Why isn't my dipole showing a more expectable impedance? Any guesses? Craig 'Lumpy' Lemke www.n0eq.com |
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