"Channel Jumper" wrote in message
...


"Sal M. O'Nella[_4_ Wrote:


. . . 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.



I would venture to say that the reason why you had a problem was due to
the fact that you used plastic pipe and a piece of wire as opposed to
using aluminum tube.

The relative permittivity or dielectric constant of the copper as
opposed to aluminum tubing probably caused a mismatch.
If the wavelength is too long - you simply cut it down to match the
frequency desired.

All a Moxon is - is a folded dipole antenna.
Its design causes it to have a little directivity, which causes it to
pretend to have some gain.

A dipole at 27.250 is probably somewhere around 18' long.
Doing basic Algebra - if two sides were 6' long and two sides were 3'
long, the length of the whole antenna would be 18'..

Why buy a program when you can figure it out yourself?

If a quarter wave stainless steel whip for 10 meters is 3 inches shorter
than for 11, all you would have to do is subtract about 6 inches from
the length of the dipole antenna.

I would have used two stainless steel whips as a dipole before I would
have made a Moxon.

Then again, they are calling for a 20% chance of rain where I am going,
and it has not gone more than 3 days all summer without a rainstorm or
thunderstorm so I would predict that 10 meters is not going to be open
for Field Days this year.

Lately the only useable bands has been 40 and 80 meters during the
daylight hours.

We had a 6 meter band opening the Thursday before the VHF contest two
weeks ago and some tropospheric ducting the Saturday and Sunday morning
of the contest. Between the lack of real hams and the weather
conditions, there has not been a lot to listen to on 6 meters in a long
time.

=====================================
Yes, I was concerned about the pipe. I know it affects VHF/UHF elements but
I thought I'd try it. Yes, I did trim it to resonance at 10m.

I made the Moxon choice because it was different from any prior antenna.
Last year a 20m quad; year before a 20m dipole. I get around.

True, the calculations are all in books, but not predictions for patterns,
SWR, etc, which is what I like about the program.

We have a 0% chance of rain and about a 90% chance of hot.

I may not work very many people but that's the breaks. Before I upgraded, I
worked VHF/UHF for years but our latest FD site is NG for VHF/UHF -- no
elevation, which was discouraging. I moved to HF.

"Sal"
(KD6VKW)