I try to take a new antenna to Field Day every year. This year I decided on
the Moxon, AKA the Moxon Rectangle. I signed up for 10m Phone, figuring I
could build that antenna and it would be small enough to be transportable.
I began reading about the Moxon design a few years ago but this was my first
time to construct one.

I drive a van. For a long-past antenna takedown party for the widow of a
Silent Key, I made a wooden frame to add length to my roof rack, about 8
feet, total. The Moxon antenna is 12 1/2 feet long, so my frame should
work.

My Moxon structure is PVC pipe and the elements are #14 wire. The
dimensions fall out of a program called MoxGen and they will come out as an
EZNEC .ez file. Nice. (I bought a licensed download of Roy Lewallen's
EZNEC for the occasion.)

I noticed a couple of things I didn't expect. One, setting the EZNEC height
of the horizontally-polarized Moxon anywhere from 0.2 to 1.0 wavelengths
above ground seemed to affect only the radiation pattern in elevation
view -- including take-off angle, upward-pointing lobes. The resonant freq
didn't seem to change much , which surprised me. I've found a common dipole
to be quite sensitive to height vs. resonance. Does the addition of a
parasitic element, in this case a reflector, make the height-above-ground
less influential?

Two, MoxGen seemed to produce a model that was too big . . . and EZNEC
seemed to agree. However, when I built the antenna, it came in around
27.600 MHz, not the 28.4 I asked for. My elements were all cut and
installed to tolerances of a millimeter or two, although I don't know what I
should have had for bend radii -- I just shaped the bends around my finger
so the measured bend point was halfway though the bend. After I checked it
with the analyzer (AA-54) I trimmed the elements and I have a nice low SWR
where I want it.

The Moxon is supposed to offer a few dB gain over a dipole. Its selling
point is a high F/B ratio, exceeding 15 dB. I can aim to Hawaii, for
example (from San Diego) and all of North America gets two S-units quieter.
Whether 10m will be open for Field Day remains a question, I may sit next
to the coffee pot for more time than I spend logging contacts.

Aside: I looked in EZNEC for a quick way to change the height of an antenna
model and found no obvious signs so I just "arrowed-down" through the
"Wires" table and changed all the Z-axis numbers. With only twelve entries,
it was not bad -- this time. Is there a hidden trick to quickly alter the
height-above-ground an EZNEC model? Yes, I could email Roy but he has other
things to do.

"Sal"
(KD6VKW)