In a message dated 8/20/01 6:06:46 PM Pacific Daylight Time, 2@vc.net writes:
<<
>
>Have been thinking of installing a simple antenna to
>cover the SE in contests and as a backup in general.
>Was considering a inverted vee hung from the tower and
>fed with ladder line & tuner. I want to cover only 10
>thru 40. My question is this: my tower is about 100
>ft ftom the house and want to feed this antenna with
>ladder line near the ground, how do I handle that
>transition to coax?
An efficient way to ground-feed a 1 or more halfwave inverted V is with a
remote controlled L-network. Fair Radio Sales sells a Collins c. 30uH DC
motor driven variable-inductor that wurks well for such applications. I
used one in conjunction with a PM-DC gear-motor driven Johnson
air-variable cap. This type of antenna is the "Hertz". It works well on
other band where the antenna is multiple halfwaves. Feed-Z at resonance
is 2000-ohms, depending on wire diameter. (Larger diameter wire lowers
the resonance Z.) Thus, a fairly simple ground connection will work to
perfection. However, ground rods do not make the lowest-R HF ground.
U.S. Army anti-tank mine research found that HF-RF typically disappears
inches below ground. So ground rods do a better job when they are buried
horizontally just under the surface.
Cheers, Gale.
> A 4:1 balun, a 9:1 balun, other?
>Is it even worth doing with the losses incurred due to
>the mismatch in 100 ft of coax? Maybe a trap dipole
>or inverted vee would be more appropriate? I just
>wondered if anyone had tried something similiar and
>how it all worked out.
>
>73, Stew K3ND
> >>
You are right about copper rods do better burried horizontal a few inches
below the ground. That being the case why not just bury wide copper sheet a
few inches below the ground? The area is several times larger. k7gco
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