As a portable operator, my antenna system and the accoutrements necessary to get it deployed are at the core of my decision making processes.  If you watch my videos or read these posts, you know I love putting a wire in a tree. First, it packs small – 67-ish feet of simple wire, a 49:1 transformer, and a throwline will fit in any pack.  Second, it’s simple and fast – throw a line over a limb, attach the wire, and hoist it up.  Easy Peasy Lemon Squeezy.

But, I’ve activated in 135 different parks now, and if I’ve learned anything, I’ve learned they’re all different.  They don’t all offer a tree for our End Fed convenience.  So, for drive up parks, I pack multiple choices, 40m half wave, 20m half wave, a non resonant End Fed Random Wire, 17ft whip and radials, ham sticks, an ATAS-120A.  A veritable cornucopia of antenna choices!

That is until there’s travel involved.  Then space can get really limited to what I can fit in checked luggage.  Or what I can cram into the back of an Outback wagon – along with the XYLs luggage, an ice chest, a giant fan, a herd of pillows, and a 75 pound, backseat patroling, Labrador Retriever. 

Suffice to say, antenna choice is just that – choices – when you can’t pack everything, it takes a little discrimination, some compromise to assure a successful activation.  And I’ve found a new and attractive choice.

KJ6ER, Greg Mihran, is the developer of the POTA PERformer.  The POTA PERformer has been well received by the Internet with several videos and articles describing the build and applauding the performance.  It’s an elevated 17-foot whip with a pair of elevated and tuned radials.  A pair of radials – meaning two instead of a dozen.  I haven’t gotten around to trying it.  Something about running wires parallel to the ground and four feet high in a public park seems …. problematic.  In my experience, muggles are drawn to wires and they’ll walk miles just to limbo under a wire.

KJ6ER’s POTA Challenger is something different. It entails a 25-foot whip antenna and a single wire on the ground.  Instead of a 1/4 vertical requiring the other 1/4 wave as a ground plane, the Challenger is a dipole in an L configuration.  More specifically, it’s an Off Center Fed, OCF dipole in an L configuration.

The ODF Dipole is a halfwave antenna, but it’s fed “off center”, at about 1/4 of the radiator’s length instead of the center.  The impedance is about 200 ohms so the system needs a 4:1 UnUn at the feed point.  The OCF dipole is nothing new, it’s feature in decades of books and articles.  What Greg has done is make the longer, 75% element from a 25ft vertical whip, elevated it, and made the shorter 25% element into a linked wire run along the ground. He had me at one wire on the ground!

The genius is in the linked element on the ground.  Remember, this is a dipole so to change bands, you have to adjust the length of both elements.  The whip is easily adjusted, like you do with your portable, 1/4 wave vertical.  The other half is made by cutting wires with lengths for each band and linking them together.  The whole setup is 20m and up so to QSY from 20 to 17, just unlink the little 20m length of wire, leaving you with 17m, then use your analyzer to adjust the whip.

KJ6ER put allot of math, modeling, and field testing into defining the lengths required to make an OCF dipole resonant on each band and his instructions detail this.  Or you can be a DitWit like me and skip to the illustration and cut the lengths he lists.

Long story short – it works.  My SWR was flat on each band. The setup is acceptable and the deployed footprint is tiny.  That 25% of the dipole running on the ground is less than six feet long.  Last but not least, it performed well, though hard to say if it was all about the antenna or about the solar weather.

• Chameleon 25ft whip
• Tripod
• LDG 4:1 UnUn
• RF Choke (home brew but there are several commercial options)
  • I made the choke with a 240-43 toroid, 3 feet of RG-8X, and some zip ties.
• 6 feet of wire
• A bag of spade connectors

Read the article here. He goes into great detail explaining the why and the how. More KJ6ER designs are here.

At the end of each of his articles is a link to donate.  I sent him $20.

As Always,
TNX ES 73
DitWit