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On Mon, 27 Feb 2006 14:29:47 GMT, chuck wrote:
One more way to word the question: if you tie the open-wire lines together at the tuner/transmitter and feed the antenna as a vertical, all of the current in the line will be common-mode. Would that be less likely to cause undesirable coupling than the exact same antenna with transmission line unbalance. Hi Chuck, When you tie them together, you have to be referencing that "common" lead to something. Usually that something is ground. Common Mode current springs into existence by definition. Where did ground come into the picture? Usually through the power supply. The power supply gets it from the mains, and thus you see the origin of getting RF into the house. I wrote earlier about how a religious devotion to balancing an antenna/feed can be easily disturbed when you connect your line to the rig. The rig has a ground connection even if you didn't drive a ground rod specifically for it, nor purposely establish a ground path. Some might think that their tuner isolates their twin line feed from ground. I seriously doubt that is true. Most tuners I've seen use a voltage BalUn which design violates that form of isolation, or turns the core into a heating element, or both. Even link tuners have the prospects of not having a truly balanced connection. I would say the prospects are much better, as the designers were working toward that goal, but it is not always achieved. 73's Richard Clark, KB7QHC |
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