Of course I thought about simply bending the ends down. In my situation
the towers are about 58 feet apart. If the horizontal part was about 49
feet long, each end would be within 5 feet of a tower, both of which are
shunt fed - one for 80 and the other for 160m. Either or both of those
towers could possibly be used simultaneously with the dipole and I really
don't want vertical wires that are about 10-12 feet long parallel with
those towers and less than five feet away. Also the bandwidth is not as
good and a flat horizontal antenna beats one that is not flat. If I do
anything different I will just put up a quad loop. There are many ways to
skin a cat and some ways are better than others depending on the logistics
at the location,
Stan
On Sun, Dec 22, 2024 at 1:13 PM Jim Brown <jim@audiosystemsgroup.com> wrote:
> On 12/22/2024 7:05 AM, Stan Stockton wrote:
> > If you just draw this on paper it looks like a dipole that is 20 feet
> shorter than a normal dipole and near the ends you have what looks like an
> arrow.
>
> Hi Stan,
>
> There are lots of ways to accomplish what you're doing. What K0SN has
> described is one of them that W6GJB, W6JTI, and I have used for county
> expeditions. N6BT (the very good Force 12 designer) has built some
> interesting versions that were all aluminum.
>
> As you noted, there's minimal effect on the pattern or field strength,
> since radiation is done in proportion to current in each segment of the
> wire (nearer the feedpoint), and is minimal close to the ends, where it
> falls to near zero.
>
> As to the coax -- I suggest you model ground as carefully as possible.
> Feedpoint Z of dipoles varies sort of like an oscillation around a value
> depending on the timing reflection from the earth and its strength. (I
> learned about this from graphs of feedpoint Z in the ON4UN book.) My
> dipoles at around 120 ft over rocky soil measure in the range of 88
> ohms. An 80 dipole we rigged at 40 ft on a county expedition, also rocky
> soil, came in at almost exactly 75 ohms. In all cases, EZNEC came very
> close to the measured values. My high dipoles are all fed with a very
> good RG11.
>
> > I’ll be glad to send an EZNEC file to anyone who wants to get a better
> picture of the design. Just send me an email.
>
> Please do.
>
> 73, Jim K9YC
>
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