Tune-A-Stick Antenna
-- a wire-wound broomstick antenna --

By Douglas Boze
via rec.radio.shortwave, April 4, 1992

Recently, Don Kimberlin described a wire-wound broomstick antenna he built, and the noise cancelling properties it displayed. Intrigued, I built a similar antenna using about 226 turns of 24 speaker wire around a 1 1/16" dowel. The length of the wound section was about 27".
These materials were what I had on hand, and the speaker wire allowed the start and end connections to be at the same end. The other end of the winding was soldered together. I was surprised by the performance of this antenna, even though it was indoors rather than out. I reckon it had over 100' on it, compared to the 65' random wire antenna I was using outside.

I connected an MFJ antenna tuner between it and my DX-440. It seemed to reject most of the noise from my PC (a rather poorly shielded 20MHz 286), and even local AM MW bcs. I am, unfortunately, located in the ground wave of a 50KW AM xmtr, and since the DX-440 is prone to inter- modulation, this causes some annoyance...
Even so, I found I still needed my 7-element Chebyshev high-pass filter to attenuate the MW frequencies and the resulting harmonics (particularly from that station on the hill, at 1360KHz). Nevertheless, it was enough to make me want to build bigger and better: what I call my Tune-A-Stick!

Bolstered by the results of the test antenna, I set about designing the outdoor, industrial strength version.
I had some vaguely defined goals to meet:
a) As much wire in one shot as possible, say 1000';
b) Make it compact, even portable (well, within reason);
c) In consideration of item "b", it should be easy to connect and disconnect.
d) Make it weatherproof.

The results culminated in a 10' length of class 125 PVC pipe (2 3/8" diameter) and 1000' of black PVC insulated 20 AWG solid tinned copper wire (Carol C2028-21-01, available from DigiKey as C2028B-1000-ND).
One end has a standard 2" PVC cap, the other end, which was belled, received a 1-1/2" to 2" adapter, into which was cemented a 1/8" thick PVC disk with a gold-plated RCA jack (Radio Shack 274-852).

Assembly

Pipe: Nothing special, just used as it came from the local Ace Hard- ware. Class 125 is all you need, as this is not a heavy device. I used 2" nominal, which has an O.D. of 2-3/8". One end was belled, but only becuase it was chopped from a 20' length of belled-end pipe. You will need two (2) 2" caps, or in the case of belled-end, one cap and one (1) 1-1/2" to 2" adapter to plug into the bell.

Caps: One cap will be left as is, the other will get a 1/4" hole drilled in the center. In the case of my BE pipe, I intended to cut a PVC disk with a 1/4" hole in the center to fit into the adapter. Lacking PVC, I used a piece of acrylic. Since acrylic and PVC will not bond, I used PVC cement in the adapter. This softened the PVC enough to sort of ooz around the acrylic disk, such that it will never come out. Put a jack into the hole, and make sure you can tighten the nut onto it. Now remove it.

Put the cap(s, and adapter) on, but do not cement them! They will only be pushed on. At a point just beyond the cap, (or bell) on the pipe, drill a hole just large enough for the wire to pass through. For the 20 AWG wire I used, that was 1/16". Drill into the print stripe, to act as a reference for counting the turns.

Remove the cap (or adapter) with the jack, or rather the hole for the jack, if you've been following the instructions . Now take the free end of the wire from its spool and pass about 6" through the hole and out the end of the pipe.

Strip enough insulation from the end to make a connection to the jack, then slip the nut, and the "chassis" or "shield" washer (the one with the solder-eye), onto the wire. You can omit the lock-washer if you need to. Now pass the wire through the hole in the cap or adapter from the inside (pipe-wise) and solder it to the center lug of the jack. Now push the jack into the hole, slip the washer over the inside portion and secure it with the nut. Bend the tab on the washer toward the center to facilitate the eventual connection of the other end of the wire.

Push the cap onto the pipe (or the adapter into the bell): You are now all set to wind up a new antenna project! Really! Turn on your SW receiver, your stereo or TV, becuase you will be spending one to two hours on a truly boring task.

I just wound each turn next to each other, snugging it up as I went along. It's easier than trying to spread them out. You can count the turns if you're nuts. I think I put 1532 +/-5 on my stick. It's all academic

Now, you will have to leave enough wire to return down the length of the pipe to connect at the washer on the jack. When the wire comes off the spool, tape the last turn, and gently stretch the wire towards the jack. If it doesn't reach, unwind enough to pass the end with about 6" to spare.

You should now start at the beginning of the winding and snug it up by twisting the turns in the applied direction while pushing toward the starting point, while working toward the free end. Locate the point where the last turn crosses the print-stripe. Back off a quarter turn. Place your drill bit next to the preceding winding on the stipe and drill a hole.

Now comes a tricky part. Tape the end of the winding to keep it from exploding (and your patience with it). Poke the end of the wire through the hole _and out the near-end of the pipe_. Pull all 8-9' out. Tie the end around a heavy object, like a large screwdriver. Remove the jack-cap, if you haven't already done so, and make sure it is clear of the bore of the pipe. Pick up the end of the pipe, make sure the wire isn't in knots or tied around your cat, and _throw_ the screwdriver down the length of the pipe.

Remove the screwdriver once the wire pops out the jack end of the pipe (it will not be needed for reception ), strip some insulation from the wire end and solder it to the washer on the back of the jack. Gently push the cap onto (or the adapter into) the pipe, and cap the other end.
This completes the Tune-A-Stick!

Read on: Technical discussion on Tune-A-Stick

To support it, I made a pair of stands out of 1/4" acrylic, each about a foot high, with a hole at the top bigger than the O.D. of the antenna. This allows them to be tilted, creating a pair of splayed feet (like a sawhorse). I have a flat roof, you see.
It could be suspended by rope, but I would recommend securing the ends about a fourth of the pipe's length in from each end, as PVC is not structural, and will sag if not properly supported.
Since the wire insulation is black PVC, I sprayed the exposed portions of the pipe with a coating of black Plasti-Dip (sp?), a liquid vinyl product. Orient the print stripe down, to place the wire holes on the underside.

And that wraps it up!


Origin: Douglas Boze, The Boardwalk! - (206) 941-3124 - Federal Way, WA (FidoNet 1:343/47)