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Old April 9th 04, 07:31 PM
Jack Twilley
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"Jim" == k7jeb remove this K7JEB writes:

Jim ASCII art fails me, Jack. You can model the coax as a wire to
Jim ground, but that wire has to have all the geometric twists and
Jim turns that your actual coax takes getting to the transmitter.

That'll be a royal pain in the butt, to put it kindly.

Jim The coax shield is part of your antenna system; it radiates along
Jim with both sides of the dipole. And even at your transmitter,
Jim "ground" isn't really ground. There is a connecting wire between
Jim the transmitter case and "earth" ground.

Actually, at my station. the water-pipe ground is connected to the
antenna tuner's ground which is connected to the transceiver's ground,
but I get your point.

Jim In reality, there is no such thing as "ground" with RF.

This appears to be one of those subtleties that has slipped past me.

Jim The reason your post caught my eye is that I have the same
Jim antenna system you do - coax-fed dipole with no balun - and had
Jim to model my coax line shield to get "real" EZNEC results.

Interesting. I do actually have two current-mode baluns -- the
feedpoint has eight or nine turns of coax that were wrapped around a
coffee can before being tied down and the coffee can removed, and the
transceiver has three turns of coax through three large rare earth
magnets. How does one model those with NEC2?

Jim Jim, K7JEB

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Jack Twilley
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