>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
>
// For a station ground, I use 25-ft of Cu tubing buried just below the
surface. For the remote-controlled 160m antenna tuner, I use a sheet of
galvanized sheet metal laid on the surface of the ground.
cheers
- R. L. Measures, 805.386.3734,AG6K, www.vcnet.com/measures.
end
List Sponsored by AN Wireless: AN Wireless handles Rohn tower systems,
Trylon Titan towers, coax, hardline and more. Also check out our self
supporting towers up to 96 feet for under $1500!! http://www.anwireless.com
-----
FAQ on WWW: http://www.contesting.com/FAQ/towertalk
Submissions: towertalk@contesting.com
Administrative requests: towertalk-REQUEST@contesting.com
Problems: owner-towertalk@contesting.com
|