[OKDXA] Dipole Antenna Question

[Nelson Derks]

> I have $20 worth of wire and a 300 foot lot.

Here's your plan for World Domination on 40 Meters...

Buy a 500' spool of 10 gauge solid insulated THNN house wire from your
favorite hardware mega-store. That's about a $40 bill, but if you have 220'
of good sturdy antenna wire on hand, you can skip that part. Divide 1,500 by
the absolute lowest frequency in MHz of the band you're interested in. Let's
say 1500 / 6.9 = 217.4' so you'll cut 220' of wire. Find the exact center of
this wire and cut it again. That's your feed point. Then you'll divide 1,200
by the frequency in MHz of the band segment you're most interested in. Let's
say 1200 / 7.1 = 169', but since you don't like dealing with fractions (and
it really doesn't matter), you'll arrange the center insulator so you have
170' of wire across the horizontal top section. The balance of your wire
will hang from the center feed point and be arranged into something
resembling ladder line.

A 10' length of 1/4" C-PEX plastic tubing (plumbing aisle, it's used to hook
up water coolers and such) runs about $4.00 and can be chopped up into 1.5"
spacers with a tubing cutter. Cut plenty of them. You'll also need a bag of
6" black nylon Ty-Raps that you'll thread through the C-PEX spacers and
cinch around the two wires you're turning into a ladder line. Once you have
all of that done, haul the wire up to a comfortable working height with the
bottom of the feeder maybe 5' off the ground (4' if you're N5UW, OKDXA Ham
Of The Year, 2002). Connect your 1:1 current Balun to the feeder (Reisert or
Guanella type), then run any length of coax back to your rig.

Key up at the absolute bottom of the band (or maybe a little lower if you
dare) and take an SWR reading at the rig. It should be 1:1. Prune 2" or so
off the bottom of the feeder and check your SWR. If it's still 1:1, repeat.
As soon as the bottom of the band shows any SWR rise, no matter how slight,
stop pruning and check the top of the band. If it's a little higher than you
like, prune just a hair more but keep a close eye on the bottom end. You'll
find the low end has a very steep SWR rise while the mid to top segment has
a much slower SWR rise. A slip of the cutters can ruin the CW section before
you realize it, so go slow and watch the bottom end 'real close'.

Weatherproof your connections, haul the wire up to its final height, then
wait for that magic moment when you hear K8FU trying to bust a pileup for a
card he really, really wants...

Feel free to key up and show Mr. Frogg exactly how it's done.

As a bench project, you might consider whipping together a simple battery
charger that connects to your antenna switch and tops off the HT NiCd
battery while you're not on the air. You'll have a volt or three to play
with at the PL-259 and a voltage tripler should get you there, so I say 'go
for it'. You'll also find the AM broadcast band has a bunch more stations
than it used to, even during the day, and at night the weak ones will be 20
Over... Big wires are truly amazing.

- AC5UP