Topband: Impedance of inv l?
k1fz at myfairpoint.net
Mon Nov 19 16:23:25 EST 2018
Things are sometimes the reverse of what they initially seem to be.
When I was a very young kid I watched workers put in telephone poles, then put wire lines on them. I knew the poles supported the wires.
Later another kid said the wires hold up the poles. I disagreed, but he got me wondering. About a year later a fast driven car hit a pole and knocked
out about 6 feet of pole at the bottom, and the pole was suspended by the wires. This got me wondering for some time.????
Its well known the current does most of the radiating. Voltage/impedance at the top of a vertical can be minimized by going to a fat antenna to maximize current radiation. But
the vertical needs something to work against. Salt water is great, but otherwise most DXers go for an efficient radial field. Lower restive loss to the radials, the less power loss occurs.
A matching network can change this low resistance (impedance) to that of your coax.
On Mon, 19 Nov 2018 09:58:31 -0600, Rob Atkinson wrote:
My inv. L is 50 feet up and 70 horizontal. Wire is #14 bare 7 strand
hard drawn. 3 feet out from mast. 101 radials, two ground rods and
aluminum siding on garage strapped in to ground sys. on around 1840 Z
is 11 R and ~ 20 ohms X. A typical inverted L with a good ground
system should be down around 15 ohms at feedpoint from my experience
and rapidly change above and below the minimum reactance point. High
resistance flat antennas have an inadequate ground system.
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