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)

On 6/24/2014 11:10 PM, Sal M. O'Nella wrote:
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)


In the wire table and dialog box, click on the Wire menu and find Change
Height by...

Sal M. O'Nella wrote:
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?

Generally, yes, as the height above ground exceeds the element spacing.

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)


In the Wires window, click the Wire tab then find Change Heigth by... in
the list that appears.

FYI MFJ is now selling 15, 10, and 6 meter Moxons. The 10M version is
$84.95. I bought one, assembled it, but haven't put it in the air yet.

MFJ is claiming 3.3 dBi gain and 30 Db front to back.

It appears to be good quality for the money but we shall see once it is
in the air.




--
Jim Pennino

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.

Channel Jumper wrote:

"Sal M. O'Nella[_4_ Wrote:
;820890"]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)

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.

That would depend on whether the pipe was only used as a support as
opposed to the wire run through the pipe.

The relative permittivity or dielectric constant of the copper as
opposed to aluminum tubing probably caused a mismatch.

Unless the conductor is very small, it would be difficult to measure
any difference between copper and aluminum and in any case the antenna
was modeled with EZNEC where one can select the material.

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.

That's like saying a 7 element yagi is just stacked dipoles.

Its design causes it to have a little directivity, which causes it to
pretend to have some gain.

A proper Moxon has about 3.3 DBi forward gain and a F/B ration approaching
30 Db.

snip remaining babble



--
Jim Pennino

"John S" wrote in message ...

On 6/24/2014 11:10 PM, Sal M. O'Nella wrote:


snip

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)


In the wire table and dialog box, click on the Wire menu and find Change
Height by...


Thank you! After FD, I'll study every dropdown and menu choice. Smart is
good.

"Sal"

wrote in message ...

Sal M. O'Nella wrote:


snip


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)


In the Wires window, click the Wire tab then find Change Heigth by... in
the list that appears.

FYI MFJ is now selling 15, 10, and 6 meter Moxons. The 10M version is
$84.95. I bought one, assembled it, but haven't put it in the air yet.

MFJ is claiming 3.3 dBi gain and 30 Db front to back.

It appears to be good quality for the money but we shall see once it is
in the air.


===================================

Thank, Jim. I do think my modeled gain is a bit too rich. I doubt that I
will ever build a conventional 10 m dipole and then do a side-by-side
comparison.

Except for the #14 wire and one bamboo support, mine is all left-over parts
from other projects, which kept the cost down (along with other things, like
quality, durability and ease of assembly, hi-hi).

"Sal"

"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)

"Sal M. O'Nella" wrote in message ...

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.

snip

The antenna worked as advertised but band conditions were bizarre. At
first, I worked a half-dozen nearby stations on direct wave. Next, I
started hearing KH6RS about 5-5 off the back of the antenna and worked him
easily. He was on the band virtually all the time. I could sometimes hear
the NA stations he was working but just barely. I logged a few other Hawaii
stations -- but not much else.

After about four hours of that ****, I tuned a strong beacon station and
watched his signal strength for a while, observing little or no variance. I
had a turning rope on my antenna and I found I could peak the beacon at S-5
to the Northeast and null it to S-1 to the Southwest. This told me the
Moxon's vaunted F/B ratio was present and it should be working. My compadre
on 15m wasn't having much better luck. It was all very frustrating.

Eventually, I went home to sleep and came back the next morning. I began to
operate again around 8:30 Local to much the same nonsense. The band changed
shortly after 9:00 AM. I started hearing the Pacific Northwest coming in.
I easily worked about a dozen stations in Washington and Oregon. One of
them was even 5-over, off the side. For the next hour, FD was like
bowling -- I just kept knocking them over! I would have kept working but
people were coming over like a parade, all wanting to talk to me, so I hung
up the mike shortly after 10:00.

We logged over a mesh network with N3FJP's Field Day 4.2. The only hitch
was the program's demand for the registration number on two of the client
computers. Our FD chairman had to make a forty-minute R/T home to get the
number. During multiple dry runs at his house, the problem NEVER appeared
once, so it was a complete surprise. I'm pretty sure our chairman is going
to ask N3FJP about it.

"Sal"
(KD6VKW)