[OKDXA] Dipole Antenna Question

[Nelson Derks]

A flat top dipole at resonance will come in around 72 ohms with little to no
reactive components. You'll see an SWR minimum of 1.5:1 at the sweet spot.
Droop the ends into an inverted vee and the impedance will drop down near 50
ohms while the pattern goes toward a fatter figure-8 and becomes almost
omnidirectional. One trick I've seen is pruning the dipole as a flat-top
until the SWR dip is where you want it, then drop the ends until you hit an
angle that gives you a 1:1 SWR at resonance.

But, being from Claremore, you want to go the other way...

If it was me, I'd fix a horizontal pipe up on the tower that sticks out
maybe 4' or so and hang a pulley on the end. Rig a rope so you can haul the
feedpoint up and down with minimal effort. Now... Here's the sneaky part:
Instead of pruning the ends (like you've always done), cut the wire a foot
longer on each side and let the extra wire hang from the center insulator
like a short piece of ladder line. Add another insulator at the bottom to
keep everything straight & pretty, then prune this wire section instead of
the ends. It saves a bunch of time... This also allows you to put ropes on
each end of the antenna that tie off to a pair of 10' pipes with eye-rings
on the top so you can tweak the angle of the dangle just by adjusting your
knots on the pipes. I've found you can wrap a rope around a pipe maybe six
times, then loop it through itself, and it will cinch up tight enough to
stay exactly where you want it. Play with this and you'll figure it out.

Also... If you have the room... A 20 Meter Extended Double Zepp is 41' each
side of the center insulator and will load with a dead-flat 1:1 SWR across
almost the entire band. They hear 'real good' and work damn near everything
they hear. You'll want to spread the ends out as far as you can, as it
prefers a flat top, but can tolerate some doodling to fit your lot. I also
had a 15 Meter Extended Double Zepp up for a month or so that was very good
on 15 and not bad at all on 40. A true EDZ on 40 is 170' tip-to-tip, and if
you can squeeze one into the antenna farm, you'll be tough to beat in a
pile-up and will peg your S-Meter on more that an few SWL stations.

I like to have at least one big wire for general purpose RX and a 20 Meter
EDZ or Off-Center Fed Dipole (coaxial Windom at 136' tip-to-tip) can fill
the bill. If I had the room, I'd go for the 40 Meter Extended Double Zepp
just to see what it could do... I'd be looking at maybe $10.00 worth of wire
and a Saturday afternoon to find out.

- AC5UP