I was recently gifted the RadioWavz DX40 Short sans wire. I have the balun and the wound inductor, but can't find any information as to the proper lengths of wire for this antenna.

I can find general information for building OCF dipoles, but this is a special dipole with that inductor doing something that is above my knowledge level.

  • $\begingroup$ There's probably no general theory that can answer this question — it depends on the specific properties of the inductor and the matching network. Therefore, you will need to know the design of this specific antenna, and I've edited the title of your question accordingly. $\endgroup$
    – Kevin Reid AG6YO
    Mar 2 '16 at 18:00
  • $\begingroup$ Have you asked RadioWavz? I cannot imagine a situation where they would not tell you. $\endgroup$ Mar 9 '16 at 15:15

It appears that the inductor is used specifically to shorten the long leg of the OCF so that the feedpoint is still in the right place electrically even though the physical size of one leg is different.

Generally OCFs work with roughly a 2:1 ratio for the two legs, but looking at the photos, it appears that they've loaded it such that both legs are now equal. Try two lengths of wire 18.5' long, then split one of them roughly in half and install the inductor. So long as that coil isn't a trap (is there a capacitor in that piece of pipe?), it's unlikely that placement of the inductor is critical.

Your antenna will look like:
----18.5' wire----[balun]---9.5' wire---[coil]---9.5' wire---

Check your SWR. If you're close but not quite, try moving the inductor a little closer or further away from the feed point and see if it dials in.

  • $\begingroup$ So I tried this, threw it up in a tree about 5ft up, and the antenna isn't even close to resonant. I can't even get it to tune with my tuner. It will tune to 20m just fine, however. $\endgroup$
    – Patrick
    Mar 16 '16 at 0:06

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