...listed in chronological order with newest message last.
 

Note:  Click HERE to post an email to the MOXON Message Board

 8/27/2003

 

You may already be aware of this, but if you are adding a 20m Moxon to a 17m Moxon severe interference will occur to the inside Moxon. At least this happens with 50 ohm coax feeds. I have not tried feeding the Moxon with ladder line. LB Cebik has come up with several ways to accomplish this. However, he recommends skipping a band for nested Moxon's (i.e. 12/17, 15/20, etc.) for best results. See http://www.cebik.com/mox1712.html. I have modeled all three versions, and I agree that the last one presented (stubbed array) yields the best results. The 50 ohm feed is at the inside Moxon with a 70 ohm 0.8 VF transmission line to the outside Moxon. I haven't come up with a practical method of accomplishing this with the wire (Black Widow) version as it would require a more complicated support system. Perhaps some ingenious builder can come up with a practical idea. If your group has figured this problem out, I would like to know the solution!

I have modeled a nested 15/20m Moxon with separate feeds and still get poor results on the inner Moxon. This translates to about 1/2 the gain and 1/5 the f/b of a monoband Moxon. I would expect to see the same or worse on 17/20m. This is the one disadvantage to an otherwise excellent antenna.

 

73,

Allen Baker, KG4JJH

8/27/2003


Since I put up the moxon in place of the folded x-beam,  stations that remember the signal from the x- beam are telling me the moxon is by far the one.  I have seen on the average of 2 to 3 s units better.  I added the garden stake to support the center of the reflector, great idea.  My coax is fed thru 1/2 in pvc pipe to the feed point and wire wrapped.  I will be putting a balun on becaue I am slighly getting into the TV.  I was doing some work on the computer late the other night about  midnight and kept hearing faint voices and whistles at 18.140.  I had  the moxon pointed SW and put out a QRZ.  V73B,  Buzz came back to me and gave me a 5-9.  It may be magic but I am hearing a lot more with this moxon.  Last night I called KH6BB, working from the USS Missouri in Pearl Harbor.  Ned said my signal was extremely strong compared to other stations he had been working.  I just finished a QSO with Frank in Calif, K6KS. He mentioned several times about my signal. Even told me he could hear me without an antenna hooked up.  I must be in a good location for the angle of take off.  One thing I have seen, signals from Tasmania are not as strong as the x-beam.  I will observe a little longer.  Bad news is, my center support is drooping from the weight of the poles.  I got a bad piece of plywood from the wire spool end.
I am now looking for a 18 in dia fiberglass hub.  don't know if I want to use the 18 in dia aluminum plate I had made up.  My goal is on a 50' pushup, stacked moxons, 20m at 30ft and the 17m at 40ft.  Oh, I can't see whereby lifting the sag in the reflector helped.  If so by very little.
Really enjoy this and everyone I talk to is very interested.  This project is growing!!


Please pass along until I can figure out this Webtv-email system.


73
Ron

8/27/2003

I have gotten emails on why we decided to use crappie poles for the antenna project instead of available 6 and 8 foot poles from antenna manufacturers.You might add the following to the webb site.

 

1) the crappie poles because they are tapered, they actually droop less than the pultruded poles offered by quad manufacturers.

 

2) The crappie poles weigh less than a pound each at 16 feet in  length. This means a light weight pushup mast can support them and an economical rotor (radio shack) can turn the beam.

 

3) The crappie poles have much lower wind area for a given length. This is because they are tapered.

 

4) The crappie poles slip down nested to less than 46 inches down in length. This makes them great for portable use.

 

5) Economy.  A sixteen foot crappie pole is $10.00 and a standard spreader would cost about $40.00 each for a single 16 foot with 3 sections. This means the difference of  $40.00 for crappie pole spreaders for a Moxon versus $160.00 for standard spreaders. Or about $50.00 for a complete antenna. Shipping of the crappie poles is much cheaper.

 

6) Availability.  Depending on your area of the country, crappie poles are readily available. If not you can arrange to get some through the Moxon project.

 

7) Stealth. With a coat of  white household paint primer, and a bit of  gray paint splatter, the moxon made with crappie poles is relatively inconspicuous.  The color combo will vary depending on your area of the country and if you have trees, etc.

 

73's

John kd6wd

08/29/2003

I visited your website concerning the Moxon. I believe the antenna can be made using RG-58 coax to take advantage of the velocity factor .66 verses .95.

Using RG-58 not only would reduce the size, decrease noise and result in a 30% reduction in size.

I down loaded the moxon program, but the program does not allow for using coax rather than AWG.

I am going to build one, but it will be constructed from RG 58.

Hope to here you on the band

73
John / N0KHQ / St. Louis

Always on 17M
Antennas:
You can build 'em better than you can buy 'em.
Visit www. Hamuniverse.com - then click on Antennas

09/01/2003

Yes this project is a lot of fun and its quite rewarding to read from happy builders.
IF it was only for the commercial side (selling a few kits) I would have had to drop this project long ago... :-)  For sure it generates _a lot_ more work than ever suspected.

You are right on the poles. Fishing suppliers know how to make money...
I had to order even a larger quantity.

About the center piece, lets keep in touch if you want. If you are interested in adapting it to your needs (as your fiberglass poles meet at other angles than those for the spider beam)
it might be easy to ask my manufacturer if he is interested in making some for you.

BTW, one of my next projects might be a single band lightweight 40m MOXON, so the center cross might have to be modified anyway.

Dont know yet if a MOXON can also be made with the supporting structure I have now (square shape), but I think if one wants to gain full advantage the MOXON is better made as a rectangle...

Good luck & 73s
Con DF4SA

09/02/2003

We had more than a few Murphy's at a minimum yesterday. The temperature was well above a hundred here on the plateau.  The plastic pole holder turned into a fiasco.   The heat caused the plastic cutting boards to bend over a quarter of an inch end to end.  We spend about 4 hours messing with them and add-ons to stiffen them.  They ended up weighing more than the metal pole holders and do not appear to be worth the trouble for any ham to mess with.  As an experiment Bob used a sledge hammer to beat flats into conduit. He then used a trailer hitch to increase the bend to 22 1/2 degrees. Total time for fabricating a  bracket from raw material about 1 hour.  Time on the plastics was about 3 hours.  The plastics required a lot of special tools to fab. Hole saws, radial arm saw, 4 different drill sizes and two people to put them together. One version require a router. Total holes on the metal brackets was 10  and total holes on the plastic bracket to get it stiff enough was 48 and required a bunch of support screws for stiffeners.  In conclusion the metal bracket is the cheapest and lowest hassle of any of them.  ab0yy or Martin's setup appear to be the cheapest and easiest to fabricate out of something that is not metal. The fiber reinforced plastic panels are far to expensive (about 36 dollars per square foot) and are heavier than the metal bracket we now use. Plywood is more rigid and lighter.

 

Now to the 17/20 meter moxon.  The original one was fabricated out of  3 sizes of  Pvc sprinkler pipes. I used radio works kevlar-dacron 3/32 string to support it from a  3 foot  high extension post above the mast bracket.  I threaded 12 gauge wire thru the pipes and soldered 20 gauge wire to the end for the tails.  This gave me a x-beam on 20 meters and a moxon on 17 meters.  This setup was not too bad.  I then added a short length of ladder line from the moxon feed point to the 20 meter feed point, though this was not perfect the swrs dropped to about  2 to 1 on both bands.  I used 6 radio works  type 34 chokes end to end attached to the coax near the feed point and this kept the feed line from radiating and I had no more rf in the shack at about 400 watts with my al811. Since I did not bother to try front to back with this setup ( I didn't have a rotor on the radio shack mast) I only could point it in one direction and just work stations.  The originally one used  1/4 inch coax  I am now using  1/2  inch 211 right now.

 

My conclusions:

 

1) Since the original design had the elements at angles to each other,  there was minimum interaction between the two bands.

 

2) the pvc pipe allowed the 20 meter elements to average about  2"  separation between the elements where they intersected.

 

3) The original 17 meter moxon was out of 20 gauge bare copper wire.  I used the 16 gauge wire on what you guy's got so you could run well over 500 watts.  According to w4rnl you can run a kilowatt on 18 gauge.  Rather than fry an amp, I thought 16 gauge tinned would give a safe margin.  This change in wire gauges caused more droop than my last 17 meter only moxon with 20 gauge bare copper and crappie poles. 

 

4) The slop in the original pvc pipe version with 20 meters on it and this probably helped reduce interaction between the two bands.  It sort of gave separation similar to that on a hexbeam.

 

5) I should have kept better records and taken pictures of the first version. This would have allowed me to give you guy's a better idea of what I had thrown together.

 

6) Tests with overlaying a moxon with an xbeam indicated that different styles of antennas could be on the same support structure.

 

7) Originally, I had hoped to get  12,17 and 20 (my favorite bands)  on the same setup. When I saw the "Black widow setup",  I made the assumption that with longer fishing poles, I could get this to fly.  The intent was to use hexbeam layout for 12 meters,  moxon layout for 17, and xbeam layout for 20 meters.  This way a three band beam antenna for under 50 bucks, a group test (all you guys), and a group article for QST.  I than proceed to search the net for Chinese manufacturers of poles.  I found a couple of sources of poles up to 7 meters.  A friend of mine ( who is in the import business)  looked at some when he when to china, brought me back 5 of them and setup me up to get the first cases of 25 each.  The first tests with 20 gauge on 17 meters using  the crappie  poles worked very well on my quad tower at about 40 feet, and that is when I started requesting  you guy's to volunteer for this project.

 

8) Original  17/20 had a 100 feet of  1/4 inch feed line.  I have no idea of what effect this had on the 17/20  meter setup

73's kd6wd

09/02/2003

Care and feeding of your moxon:

If you plan to leave your moxon up as a permanent installation, the following is recommended:

Protect the fiberglass poles with paint. I suggest using exterior house primer. Failure to do this will result in deterioration of the fiberglass. Instead of using tywraps at the wire junctions use a light gauge steel wire and a dab of epoxy. Seal up all coax connectors well. Water leaks in to the coax will give you a dummy load and not an antenna.

Preparation for painting: disassemble each pole to its individual elements. Then using a fine steel wool or very fine sand paper sand each segment of the pole until it is dull in appearance. This will remove the light wax layer that exists and allow for good adhesion of the paint. Then reassemble the poles, extend them fully, and paint with a light layer of paint. I painted one set of mine white with house exterior primer, splattered them with a light gray, and they were all but invisible from the street.

Safe placement of your moxon is important. So is common sense. Keep the doggone antenna away from the power lines to your house, and power lines to your neigbors house. This antenna plays like a champ at 20 feet with a hundred feet of rg58. So there are many options for mounting. Chimney mounts with a 10 ft mast and a rotor work well. Just use 4 straps instead of two for the chimney brackets. Phillystrand or dacron guys work great without detuning the antenna. So make sure that if the short push up mast should ever come down, it will fall on your property and clearly miss powerlines. If you have children or have children visit you, make sure that they cannot accidentally knock your mast over. This moxon has a wind area of less than 3 feet and is less than six pounds in weight, but should anything of even that light weight fall from 20 feet it can cause serious injury or even death. If you are new to ham radio, get another experienced ham to check things out for you.

 

73's kd6wd

10/19/2003

I thought I would drop you a line for the site. I built a moxon for 15m this weekend---works great. I used bamboo poles and #12 insulated copper stranded wire. The antenna is up about 35 feet and rotated with, what else, a radio shack rotor...

 

My first conatact was a G4 who gave me a 5-7 report...later in the day I worked 9J2BO in Zambia and C5Z in The Gambia. Infact, I have worked more DX into Africa with this antenna than I have in over 20 yrs of hamming. None of this would be half as impressive if it were not for the fact it was done with my FT-817 at 5  watts.

 

To say I am impressed is an under statement . I still have not figured out the fronto to back business yet but it is apparent...although strong sigs seam strong in any direction and every time I try to test a weak one QB messes up the test...nedd to get a local station and maybe do some tests.

 

Mant thanks for the site. I appreciate any comments concerning the front to back tests.

 

cheers,

 

scott

VA3ZW Rockland, Ontario

11/28/2003

I built a Moxon rectangle beam following the advice on your Murray State
site. It is performing about 2 -3 S units over my Sigma 5 vertical dipole
and my horizontal 88' NE-SW ladder line fed doublet.

I took an old fiberglass pruning pole and cut 1.5' lengths of the larger
diameter pole and wrapped duct tape around the bottom of the crappie poles.
Then I used an old paint brush and painted epoxy on the duct tape and then
force - fit the crappie poles into the pruning pole sleeves. I took 2 pieces
of conduit (bent using a conduit bender to just the right angles) to make
the metal spreader bracket and wrapped these with duct tape and then force
fit the fiberglass sleeved spreaders onto the conduit and drilled a hole and
bolted each spreader onto the conduit. Finally, I used a couple of round
radio shack push up pole guy rings and sandwiched the spreaders and their
bracket  so they wouldn't tip side to side and put one bolt through the
sprader bracket and through a remaining piece of a fiberglass pruning pole.
That was put into a cheapo radio shack tv rotator.

I used one of my sons varnished pine arrows for the insulator between the
driven element and the reflector.

I used an MFJ 259B to make sure it was resonant on 17M, and using the
windows calculator - it worked just as planned and designed. I use a
Heathkit tuner on all bands between 20 - 10M, where I am assuming it acts
like a rotatable dipole on bands other than 17M.

Thanks for a FANTASTIC site and 73,

Rich
KY6R

12/07/2003

For some months I have been reading about the Moxon and of course found
your web site most interesting. I have been a ham for 46 years and operate
cw most of the time when not building antennas. For 30 m I have a delta loop
and a half square (another very interesing antenna), 20 to 10 , 3el and 2el
beams, dipole for 40 and for 17 m I have been using a delta loop and a
ground plane. My goal has been to have two antennas designed for each band
so as to have a basis of comparison. At long last I have a 17 m Moxon up at
25 ft. and am using the 17 m delta loop as the comparison.
Unlike other builders I decided  on a "radical" approach to the
construction in that I did not use the normal x configuration but rather I
built what I call the MBB1 ( Moxon Bamboo Beast 1) using parallel bamboo
polls as an attempt to reduce the droop that was apparent with many of the x
configurations. I used #14 covered wire for the elements and the wire does
double duty because I use it to stress the polls - a counter stress is
provided by heavy duty plastic line used in lawn trimmers. To eliminate sag
on the "bent" section of the rectangle - and to maintain parallel elements 
I have used small wooden rods that are bent to produce continued stress
against the two long sections of the beam. I built the beam "by the book"
and took a great deal of time to make it "just so". For example the bamboo
polls were first wrapped with electrical tape before they were painted.
I was feeling quite proud of my design changes as I anticipated sending you
an article of my great achievement until I attached the swr meter and found
that at design freq. of 18.120 I had swr of 2.2 - how could this be! I was
sick and then shocked as I continued to do a plot to find a swr curve and
found that my MBB1 was 1.2 swr 720 Khz below design freq. Well I ran down to
the computer and decided to "scale" the antenna by designing it for not for
18.120 but rather 18.840. By this time the rain in Louisville was turning to
snow and let me tell you that my hands were quite numb as I climbed on the
roof to trim all four ends of the antenna. Then to solder under such
conditions was even more fun. I would use a rag to dry off a section of the
wire and apply heat from the iron - the wet wire would sizzle as the
rain/snow boiled and then I would apply the solder. Only a very sick person
would do this but alas this must be what has been referred to as Moxon
Madness and by this time I had a terminal case.
Well now my MBB1 is 1.4 at design freq. although it is still too long
because it is down to 1.2 at 17.960 but at this point 1.4 is something I can
certainly live with. For the last 24 hours I have been comparing the Moxon
against the Delta Loop on receive. As you know a full wave loop they say has
gain over a dipole and I have found loops to have very good signal to noise
characertistics. The loop is broad side to Europe at 50 degrees so it is
most fair to compare the Moxon when it is at 50 or 235 degrees. Thus far I
am seeing useful gain with the Moxon in the order of 1 to 2 S units (often
much greather) but as you know with very rapid qsb on 17 often your
objective efforts become subjective as you switch back between the antennas.
As regards the mystery of the radical frequency adjustment required I can
only guess that the wire being so close to the polls may be a factor. I am
using an in line choke and the boom is wood. One good feature of the MBB1 is
that my Moxon is considerably shorter than its brothers although I retained
the boom spacing as originally called for thinking that that would not have
an adverse effect. Thus, I am only just beginning to evaluate this beast and
can only wonder what the net result is of my screw ball design is. Is my
Moxon up to par with a normal Moxon - was my quest to eliminate sag via my
"radical" design a fools folly - maybe sag is not such a bad thing. At this
point the only thing I know for sure it that I definitely have a very bad
case of Moxon Madness and W4RNL would no doubt get a laugh reading about my
improved Moxon - The Moxon Bamboo Beast.

73 de Hal KA4SDU

03/04/2004

Assuming you want to build a coax element MOXON with a design center frequency of 7.260mhz:

 

Driven Elements = 650 / 7.260 = 89.532' / 4 = 22.382' cut (2) pieces of coax to this length.

                           When you measure these lengths with the 259B they will be further

                           reduced in size due to resonance.

 

The Reflector Element will be 5% longer than the total length of the (2) Driven Elements.

In other words, lets say you end up with each Driven Element being 22' long. This equals 44' total x 1.05% = 46.2' Reflector cut length.

 

Each Driven Element will bend to form the tail. Once again, assuming a measured element length of 22'. Only 30% of the element needs to be bent to form the tail. So, 22' * .30% = 6.6'. Each tail section on the Driven elements will be 6.6' long. Leaving 15.4' of each Driven Element for radiation.

 

The Reflector Element will be 30.8' straight across and each tail will be 7.7'. This totals 46.2'.

 

Driven Element to Reflector Element spacing should be between .20% and .15% of a wave length at the design frequency. For our example, assuming a design frequency of 7.260,

984 / 7.260 = 135.537' * .20% = 27.107' (way to wide) so, 135.537' * .15% = 20.3' (still way to wide). As you can see the spacing between the DE and RE is something that we cannot do anything about it if we are to have a reasonable amount of Front to Back.

 

If you use the 9' that N5GLR used you will end up with an antenna that exhibits a hell of a lot of forward gain but the F/B ratio will suffer.

 

Is that a bad thing? Not necessarily, if you live in the center of the USA like I do, then maybe you want to hear whats going on out West when you have the antenna pointed East.

 

In any case the antenna will out perform any Hex or "X" beam out there, and don't forget, the entire array will be 30% smaller than its AWG brother.

 

I would build one, but my total air time on 40m is 2hrs. per week and I use the Sterba Curtain for that. Most of my time is spent on 17m and 75m.

 

Have fun Steve, and keep us all up to date on your progress.


73
John / N0KHQ / St. Louis

Always on 18.130

Antennas:

You can build 'em better than you can buy 'em
Please visit the sites below:

http://www.hamuniverse.com/17mcoaxmox.html
http://www.cebik.com/n0khq.html
http://www.ssb-audio.com/forum/

03/20/2004==>LESLIE A. MOXON, G6XN, SK

Leslie A. "Les" Moxon, G6XN, of Surrey, England, died March 3. He was 95

and among the oldest Amateur Radio operators in the UK. Licensed in
1928, Moxon was well-known among the amateur community for his writings on
antennas, in particular his 1982 book HF Antennas for All Locations, now

in its second edition. ARRL antenna specialist Dean Straw, N6BV, called
Moxon a "radio pioneer" and said he'd been a fan of his work for years.

"His insights into the effects of terrain were one of the factors that
got me interested years ago in this aspect of HF radio work," Straw said.
During World War II Moxon was involved in top-secret work to develop
radar. He worked for the government as a radio specialist after the war, retiring in 1969.

ARRL CEO David Sumner, K1ZZ, said Moxon's book "set the standard for
practical antenna books and remains a classic."

Moxon's son, David, recalls that his father's gardens grew antennas the
way others grew plants and shrubs, and a new antenna design was always
taking shape. "He always liked to live on the top of a hill--good for
propagation of radio waves," he said. "And when moving to their final
house in Hindhead, real estate agents were bemused to be asked about
'the long path to Australia.'"

Moxon authored a July 1952 QST article, "Two-Element Driven Arrays."
Several other of his articles appeared during the 1970s and 1980s in Ham

Radio magazine. "A 6 Meter Moxon Antenna" by Allen Baker, KG4JJH, is
among the antenna articles featured in April 2004 QST.

In later years, Moxon developed an interest in theology, and he was not
active on the air in the months prior to his death. A service was held
March 10. Survivors include his wife Nancy and his son.


-------------
Steven Hammer
K6SGH
email: k6sgh@cox.net
website: www.k6sgh.com

everything is cheaper in free space
04/05/2004

It's nice to read some articles about the moxon antennas on your website ...

About the article of F5MAG's Multiband Moxon
http://campus.murraystate.edu/org/msuarc/moxon/f5magmoxon.htm

You may want to visit F5MAG's website at www.f5mag.fr.st .
... I didn't find anything about F5MAG's antenna on his website ...
the only thing i recognized were endless windows with all kind of promotion
of his internet provider ...

Well ... now back to the antennas ...
I'm designing and using these kind of antennas now for several years
and I'm always very astonished about the performance of these antennas.

At the present time I'm using a 12/17m mixture of Hexbeam and Moxon
12m: Moxon - 17m: HexMox c/o: DF4RD - feeded with only one coaxcable.

By the way ...
Just to let You know  ... a couple of years ago an article was published in our
German hamradio club magazine "cq/DL" of the DARC.

The article is available on the web - the only handycap is ... it's written
in German ... nevertheless it might be interesting for You and the community
to click on the website and see DL2NK's design of his Multiband antenna

http://home.t-online.de/home/f.kombrink/index_0.htm

73 es hpe cuagn

de Dieter, DF4RD

04/07/2004

Hi there.  I got all of your emails off of the moxon website.  I'm a 21 year old college student making the moxon antenna, and I was wondering if you could answer a question...

 

I build the 20 mtr moxon using a 1:1 balun and, much to my dismay, when I used the exact dimensions that the moxon generator gave me, the driven element was at a 1:1 SWR about 600 hz below the frequency I typed into the generator (13.700 instead of 14.300).  I had to shorten the driven element to obtain a 1:1. 

 

Now, the question... Do I keep the reflector at the length that the moxon generator gave me, or do I shorten the reflector to the length that would correspond to the "shortened" driven element.  If I did the latter, the frequency that the antenna would correspond to, using the moxon generator, would be 15.070.  Keep in mind that I shortened the driven element to resonate at 14.300, and it is shorter than the dimension the moxon generator gave me  :(

 

I am confused.  If anyone has an answer, it would be much appreciated. 

 

thank you,

 

Garrett Ensign
KC7BEY
Bellingham, WA

04/07/2004

Hi Garrett,

 

Don't be concerned with making an error in calculations, at least you didn't have to add wire.:-)

 

Using the MoxGen software type in the frequency 14.300 and the ga. wire that you are using,  the numbers that appear will be your new wire lengths.

 

The reflector element will always be about 5% longer (lower in frequency) than the total length of both driven elements. Where as director element will always be about 5% shorter (higher in frequency) than the total length of both driven elements.

 

 

If I can be of further help, let me know.

 

 
73
John / N0KHQ / St. Louis

Always on 18.130

Antennas:

You can build 'em better than you can buy 'em
Please visit the sites below:

http://www.hamuniverse.com/17mcoaxmox.html
http://www.cebik.com/n0khq.html
http://www.ssb-audio.com/forum/

04/09/2004

Garrett,

 

I had the same problem when building a 15m Moxon using insulated wire. The actual resonant frequency was considerably lower than that predicted by Moxgen. Here's what I did to solve the problem:

 

Final Length = (Measured Resonant Frequency) / (Desired Resonant Frequency) X Current Element Length

 

Do this calculation for all dimensions of the Moxon (A, B, C, & D) and then trim your elements and spacers to the Final Length.

 

For example:

If the Measured Resonant Frequency = 13.7 MHz

and the Desired Resonant Frequency = 14.3 MHz

Lets say A = 301", B = 46", C = 7.5", and D = 56"

13.7/14.3 = 0.95804

A Final Length = 0.95804 x 301 =  288.37", so trim (301 - 288.37) = 12.63" from A

B Final Length = 0.95804 x 46" = 44.07", so trim (46 - 44.07) = 1.93" from B

C Final Length = 0.95804 x 7.5" = 7.185", so trim (7.5 - 7.185) = 0.315" from C

D Final Length = 0.95804 x 56" = 53.65", so trim (56 - 53.65) = 2.35" from D

 

Good luck, and I hope this helps.

 

73,

Allen, KG4JJH

04/09/2004

Garrett...

I feel your pain-please go to
http://campus.murraystate.edu/org/msuarc/moxon/ka4sdumoxon.htm and you will
see the same story and my answer. I can tell you that my Moxon is used 99%
for cw dx and as such at 25ft / 100 watts it does the job quite well. My
Moxon is about 3% smaller than design. Because my wire was covered I am told
that the skin effect caused this difference. This spring / summer I hope to
get a 30 meter Moxon up fixed on Europe - for now I am using a delta loop
and half-square on 30 so this will give me a A B C test of the three. With
10 antennas over the QTH why not just one more?

73 de hal KA4SDU (48 YRS ON CW)

04/10/2004

Hi Garrett (and all you moxon fans)...

 

I have built a number of "moxens" for various bands with all sorts of wire / balun configurations.

I have one piece of solid advice, 

Get yourself an antenna anayser - BUY, BORROW, BEG or STEAL !! .

It is suprising ( well maybe not ) just how things change with  wire types /coatings etc..Then if you start multi banding its even more fun !! - The moxgen is a good guidline but as they say over here, " the proof of the pudding is in the eating"       hi hi .

Enjoy desert and keep coming back for more.

 

Love my moxon

 

73 de Phil   g0wsp

04/10/2004

Hi Garrett,

 

You said that you are in college. I recommend that you go down to the campus book store and pick a book titled "Grob Basic Electronics". The sections that may interest you have to do with capacitance, Inductance, electromagnetic induction, inductive and capacitive reactance's. Its a good basic book.

 

Like one of the previous replies suggested, Beg, Borrow or Buy an MFJ 259B antenna Analyzer, this unit will tell you exactly what the antenna is doing and how to correct any faults. You can buy the unit for $200 at ham fests or look on Ebay....there is one there for sale now under "Meters".

 

One solution to your situation is to not use pvc covered wire at all. You can use 18ga copper clad steel wire, this wire is available from "The Wireman" and is very inexpensive.

 

One other note; it is necessary to install a 50ohm balanced to 50ohm unbalanced current balun at the feed point (from Radio Works). Failure not to use this device will result in an electrical imbalance of the antennas electrical radiating field. In other words, the entire shield of the coax, all the way down to your rig, will act as the other half of the antenna.

 

When checking the SWR, if possible, check it at the antenna, not at the other end of your coax feed line. If it is not practical to check the SWR at the antenna, cut a piece of feed line that is 1/2 wave length long at your design frequency. Using the latter method, you will see the same numbers just as though you were testing right at the antenna. 

 

Take your time, building antennas is fun, its not a mystery and its darn sure not rocket science.

 

We are all here to help, so keep the emails coming.

 


73
John / N0KHQ / St. Louis

Always on 18.130

Antennas:

You can build 'em better than you can buy 'em
Please visit the sites below:

http://www.hamuniverse.com/17mcoaxmox.html
http://www.cebik.com/n0khq.html
http://www.ssb-audio.com/forum/

04/10/2004

Hello All,

 

 

Antenna building weather is here, and we all know what that means.

 

In about two weeks I will have a 40m 2 element coaxial square up and running. The entire beam will weigh less that 10lbs on a 30' pushup pole and rotated with a tv rotor. The turning radius will be 16'-6".

 

Unfortunately I will not be able to build the antenna with the optimum spacing for a good front to back, but it will have a heck of a lot of forward gain.

 

I will keep the list up to date on the final construction details and performance.

 

From reading the list, I notice that a few of you are concerned about droopy elements.

 

Extend the mast 24" to 30" above the hub, put a PVC cap on the top along with an "eye bolt". I use 3/16" Dacron lines going out to 2 places on each pole....no runs no droops no errors. 

 

I personally do not recommend the use of PVC for a mast. You would do better to use aluminum electrical conduit.

 

Through the fall and winter months my fully rotatable (at 30') 17m linear loaded coaxial extended double zepp has performed very well when compared to my Sterba Curtain.

 

This fall I will be taking down the 40m coaxial beam and constructing a fully rotatable N0KHQ 80/75m coaxial dipole, turning radius 16'-6".

 

All of my designs are slanted toward those ham radio operators that, 1. do not have the room to erect full size AWG antennas, 2. Do not have a hefty tower and a hefty rotor, and most importantly, 3. Cheap. :-)

 

Thanks once again Don for the nice Message Board.

 


73
John / N0KHQ / St. Louis

Always on 18.130

Antennas:

You can build 'em better than you can buy 'em
Please visit the sites below:

http://www.hamuniverse.com/17mcoaxmox.html
http://www.cebik.com/n0khq.html
http://www.ssb-audio.com/forum/

04/12/2004

hello all:

found this while looking for a picture of les moxon.  you wouldn't
happen to have one would you?

anyway, these guys built a triband moxon and have full descriptions.
they feed all three at the same time via a small run of twin lead down
the feedline spreader.  they have good reports.

here's the link:

http://www.qsl.net/g4prs/Activity%20HF%20Antenna.htm


Steve
--

STEVE HAMMER

KG6ENA@COX.NET
WWW.K6SGH.COM

everything is cheaper in free space

04/13/2004

Hello,

I just stumbled on your moxon antenna website. Congratulations for a
great site. It is very interesting to read about the comparisons, as
they are hard to fully simulate.  Some weeks ago I made my first
stumbling attempts with a moxon to test whether I should consider
building one. After several sessions with MMANA, having Cebiks 2 meter
version on paper I scaled it for 70 cm (433.5 MHz) and have made tests
with it. The F/B-ratio is fantastic, and I really like the sharp nulls
in the back-lobe. That was I expect to be able to stop some QRM.

I haven't built a full-sizer yet but will try to later this summer.

Oh, and my antenna website is www.isy.liu.se/~mj/HAM/ANT there I have
described the Moxon as well.

I will print out and read your entire moxon site when going by bus to
and from my job.

Best 73 GL!
/Micke

04/14/2004

I have found a reliable source for crappie poles.  somewhat better
quality than the ones john got from china.

Wendell Cothran runs www.catfishsupplyco.com .  I spoke with him this
morning and negotiated a price for poles for moxon group people if we
purchase 4 poles at a time.

The prices (plus shipping charges) are as follows:

10 foot poles= 4 for $4.75 each
16 foot poles= 4 for $7.50 each
20 foot poles= 4 for $8.95 each

Our group people should call him at 931-394-3052, ask for Wendell and
tell him they are moxon people who want the 4 poles at the special price
listed above.

I have search and searched for poles and i think this guy has the best
poles out there.  they are more sturdy than the ones i am currently
using.

I hope this will help our people to find the poles they need.

Steve

K6SGH

--

STEVE HAMMER

K6SGH@COX.NET
WWW.K6SGH.COM

everything is cheaper in free space

04/22/04

Hello to everyone...

Click HERE to view a small PDF-File with some pictures of my solution of the
12m: Moxon - 17m: "HexMox" c/o: DF4RD - fed with only one coax cable.

At the present time I'm writing an article for one of our German ham radio
magazines ... so please excuse that I don't publish more details like
dimensions, etc. 'til the article is issued ...

Nevertheless, I think, it won't be to difficult for experienced antenna
designers to do all calculations on their own ... !?

73 es hpe cuagn de Dieter, DF4RD

-----------------------------------------------------------------
Dieter Dippel, DF4RD       email: dippel -at- rrze.uni-erlangen.de
Bavarian Contest Club         http://www.bavarian-contest-club.de
-----------------------------------------------------------------

05/02/04

For those of you trying to nest moxon antennas. I have the following suggestions: 

 

1) Keep the planes of the MOXON separated with considerations given with respect to the angle of radiation. 

 

2) If your elements have to be in the same plane, make sure that they are exactly in the same plane and experiment with spacing between the two driven elements.

 

3) The moxon generator program will only be a starting point for wire length. You most likely will have to trim driven elements shorter on both bands.

 

4) physical position of the higher frequency antenna will have to be adjusted and most likely will not be centered.

 

5) The unique characteristics of the moxon creates some difficulty when using many antenna modeling programs I have seen.  I have had a 17 & 20 meter moxon up and by tweaking with open line between the feed point on 17 an the driven element on 20 ended up with very reasonable swrs (1.3) and excellent perfomance on both bands and was fed with 50 ohm 213.

 

6) I have used ferrites( twin setups of Palomars economy choke $7.95 each and have multiple toroids ) and a single feed line. Keeping radiation off of the feed line is critical to performance with multibanded moxons.  In fact, the old standby 25 ft coax wrapped on 4" pvc choke flat didn't work for my two band  setup.

 

7) I do not know Mr. LB Cebik personally, but I can tell you he is a super bright individual when it comes to antennas.   Read all of his writings (even on antennas which you have no intention of building). There is a wealth of information on his webb site. It may be a bit technical, but trust me you will learn a ton.  The side benefit of all this reading is that you will get an insight into element interaction and a clearer understanding of antennas in general.

 

73's (yes I am a young guy and only send 73 on cw! HI HI)

kd6wd

05/24/04

Hello all...

Well, I took down my 15m Moxon today after a Canadian Fall, Winter and Spring. It was in surprisingly good shape and still in tune. The weather had, however, distorted the plywood support plate where  the bamboo rods met and the bamboo itself was a bit more 'droopier' than before. That aside, however, it was A-1. Not bad for 15$ worth of materials.

 

I plan to use a new design this summer--maybe an all aluminum moxon if I can manage it.

 

Cheers

 

Scott  VA3ZW

06/11/04

Hi all

 

What a great site you have going here i am very intersted is the moxon antenna,I find it hard to find spreaders or fishing poles long enough for a 20 meter moxon.I live in CANADA and was wondering what others are using for light weight spreaders, and where to buy them crappie poles sound good but i bet they are not shipable.:(

 

Thank you

Corey

ve1kco

Webmaster's comments:  Visit www.catfishsupplyco.com .  One of the MOXON participants has negotiated a price for poles if you purchase 4 poles at a time.

The prices (plus shipping charges) are as follows:

10 foot poles= 4 for $4.75 each
16 foot poles= 4 for $7.50 each
20 foot poles= 4 for $8.95 each

Call him at 931-394-3052, ask for Wendell and
tell him that you want the 4 poles at the special price
listed above.

07/04/04

Hello all,


First I would like to thank all contributors of the Moxon Project.  The Moxon is just what I needed for 17 meters. Just got finished building one, and it works great!   I strayed a little from the conventional design because I needed to mount it under an another antenna. Works great, amazing SWR, did not have to adjust it at all.


I took pictures and tried to explain it best I can and posted it on my website. Here is the link if you want to take some info off or use it as a link.
http://www.qsl.net/n2yet/moxen.htm

Best 73,
Fred / N2YET
http://www.qsl.net/n2yet
 

07/07/04

Wow!  I just finished my first Moxon rectangle yesterday evening and will post photos shortly.  It's of conventional construction using fiberglass crappie poles and #16 AWG antenna wire.  I used a 12" square of acrylic and a PVC plumbing fixture called a companion flange for the hub and mounted the antenna on a 5 foot piece of schedule 80 PVC plumbing pipe strapped to a chimney mounted TV mast.  I'll soon install a rotator.

I cut the antenna for 14.225 MHz and was downright anal about measurements.  The results have been fantastic.  I first pointed the antenna due west from my Washington, DC area QTH, tuned up on 14.300, and raised a fella in Arizona with the first call. Domestic 20-meter conditions were a pretty "iffy" at that time (8 PM local time), but we exchanged 55 reports anyway. He was running 600 Watts into a tribander Yagi. I was pouring about 100 Watts into my new Moxon from my venerable Collins S-Line.

I then climbed onto the roof and swung my Moxon to the ENE.  Predictably, the UK and the Continent came alive on my old 75S-3.  My first contact -- on sideband -- was with a gent in Italy who gave me a "very big" signal report of 59 plus. This was followed immediately by two UK contacts who favored me with 59 + 5 and 59 + 10 reports respectively. 

After signing with the Brits, I retuned to 14.030, called a short CW CQ and created a pileup -- the first in my 35-year-long ham career! Guys from France, Germany, Spain, Poland, the UK and Russia vied for my attention.  I picked up one of the Russians, who had a dipole, and got a 579 from him. He barely wiggled my S-meter, but -- because of the quiet nature of my new antenna -- was perfectly Q5.  After we signed another Russian station called me to congratulate me on my "large" signal and inquired about my rig and antenna.  I told him about the old Collins pair and my new Moxon.  I'm not sure he understood what a Moxon was, but expressed more congratulations.

Constructing the antenna was a bit more "fiddley" than I thought it would be, but well worth the two-day effort.  I learned a lot along the way and subsequent Moxons will be much easier to assemble. Oh, here's one tip that will probably be obvious to old-timers: don't allow any big metal objects to "bisect" the rectangle. At first, I mounted the antenna so that the metal TV mast was resting on the bottom of the antenna's central mounting hub. Consequently, the antenna simply would not tune up.  By raising the Moxon just three feet above the TV mast, so that the top of the metal mast was just below the wire elements, the problem was cured.  My Moxon is now essentially flat from one end of 20 meters to the other with an SWR no higher than about 1.2:1 anywhere. I am amazed at how broad-banded it is. At a height of only 25 feet above ground, it defies logic and my EZNEC modeling software.

My sincere thanks to Don for his terrific website and to all the participants who've shared their knowledge and to that very nice man in Tennessee, L.R. Cebik, who's been gracious enough to correspond with me and lend his encouragement.

73,

Craig Roberts
W3CRR

 

 
07/12/04

Hi again,

Here's a little more info on my newly completed "Moxon Lite". As I mention in the narrative, I'm planning to construct a commercial quality aluminum tubing version in the next couple of weeks. I'm thrilled with this antenna design and -- again -- am very grateful to this website for helping me with this project.

Here's my story thus far:

I have just finished my first full week of living with my new 20-meter Moxon rectangle and have found it to be the most pleasing antenna I've used in 35 years of amateur radio operation. What fun!!!

This past weekend's IARU HF World Championship contest provided a terrific opportunity to test the rookie skyhook "in battle". It proved to be a tough little warrior.  I pointed the Moxon northeast from my Washington, DC QTH and, although not officially participating in the competition, amassed scores of very easy European contacts in just two, extremely casual half-hour operating sessions.  Every signal report from my vintage barefoot Collins station was "5-9" or "5-9 plus".

Of course, I don't take signal reports given during contests at all seriously since EVERYBODY, unless completely unreadable, is "5-9".  What told the story of the antenna's efficiency was the fact that I broke through each pileup on the first or second call (usually the first) over 90-percent of the time. The only time my call went unanswered was during my very first attempt - and that was because, in my excitement, I had the transmitter and receiver tuned to frequencies 100 KHz apart (oops)!

Earlier in the week, I had swung the Moxon westward and spent an hour or so on a couple of evenings chatting with domestic brethren.  Easy, coast-to-coast QSOs were commonplace, with solid Q5 signals transmitted and received.  Most reports were 5-7 to 5-9 in both directions.  I seem to work a little better "across the pond", but that's a matter of geography, not the Moxon's "Moxie". 

The Moxon's forward gain is certainly useful, but the antenna's real strength is in its rejection of off-axis signals. When pointed toward Europe, for instance, I feel like a "local" since North American signals are either substantially muted or absent altogether.  It's a welcome respite from the chaotic band reception offered by my old standby dipole.

For the most part, construction of my Moxon is conventional. I utilized 16-foot crappie poles as spreaders and 16 gauge stranded antenna wire as elements. The wire's attached to the lightly sanded spreaders with heavy-duty electrician's UV-resistant cable ties (a Home Depot item) and a wrapping of premium Scotch 88 electrical tape.  The element spacers are small diameter lengths of PCV pipe. Here's a helpful hint regarding them, by the way. Drill a single hole on each end and thread your antenna wire through these. In other words, don't use the full diameter of the pipe when attaching the wire. If you do, the resultant loop of wire can de-tune the antenna.  Of course, using a flat spacer - like a piece of acrylic sheet - would do the trick and look better, too. That'll be an "upgrade" on my antenna.

The antenna's hub/mounting plate is a bit unusual.  It's a 12-inch square clear " acrylic sheet with a 1-1/2-inch PVC plumber's "socket flange" bolted to the bottom. The antenna is then mounted on a mating 5-foot length of Schedule 80 PVC pipe to separate it from the steel TV mast upon which it is ultimately lashed (see photo at right). It is imperative that no large metal pieces bisect the rectangle. All metal hardware on my antenna is stainless steel and kept to a minimum.  For instance, the spreaders are attached to the mounting plate with PVC conduit straps rather than the usual metal ones. That may be overkill, but I'm comfortable.

I employed a homebrew 1:1 current balun at the antenna's feed point and combated the resultant spreader/element sag by suspending the center of the driver and reflector with an appropriate length of Schedule 80 -inch PVC pipe. There's still some harmless sag, but it's of no operative consequence.  Nevertheless, for esthetic purposes, I plan to replace the strut with a piece of Schedule 120 pipe as soon as I can locate a length.  I'll also be installing a rotator shortly to save myself the trouble of climbing onto the roof every time I want to "take a bead" on a fella.

During the next thirty days, I plan to build a very rugged, permanent, commercial quality Moxon rectangle with aluminum tubing and heavy-duty PVC mounting components.  I'll keep you posted on the project and the results.

VY 73, fellow Moxonites!

Craig Roberts
W3CRR

07/17/04

Hello all...

OK, I'm convinced to give the Moxon a go...skeeters or not, here in the hot & humid Arkansas Delta.  I've been thinking about a creative way to use 1/2 of a two-piece 2 el cubical quad boomless aluminum spider I acquired recently with some type of "X-Hex-Mox" type design for 20M.  Since the 45 degree angle would put the wire a little further up in the air, I would think that could be a bit of an advantage with my small push-up mast.  But then again, is this likely to be tricky since the quad spider is configured for 'square,' vs. rectangular configuration? 

 

Another couple of questions:  Has anyone tried this technique before, and what considerations will I likely encounter?  And since I'm 99% CW, what frequency should I begin with (w/MoxGen on 20M) to provide advantageous SWR and overall performance in the low end of the band?  I was thinking about using adjustments tweaked for 14.025MHz, but perhaps the antenna is more broad-banded...

 

BTW, I've been a ham for 42 years and am amazed that I only recently "heard of" these designs...I've yet to actually hear anyone using a Moxon, but the testimonials are convincing. Is it a commercial antenna manufacturer conspiracy? ;-)

 

Tks/73/DX,

 

 

Ron, K5XK

(See W3CRR's response below)

 

07/18/04

Hi Ron,

I put together a 20 meter a few weeks ago using the usual fiberglass Crappie poles,  a 12-inch square acrylic sheet, a few PVC conduit straps (to lash the pole spreaders to the plastic sheet, and a 1-1/2-inch plumbing "companion flange" with a 5-foot PVC pipe mast.  So far, it's weathered several thunderhowers, including a severe storm with 50 MPH + wind gusts, with no problem.

This coming weekend, I'm assembling a commercial prototype using a more conventional Yagi boom and aluminum tubing element design. I'm sold on this fantastic antenna!

 

 

As for its bandwidth -- I, like you, am primarily a CW guy. I cut the first Moxon, however, for 14.225 in order to "show it off" to my buddies on the Collins Collectors' Association net (14.263 SSB).  I was astounded to discover, however, that my 'phone-tuned Moxon, had an SWR of less than 1.3:1 over the whole 20 meter band -- better than my modeling software had predicted.  If you cut your Moxon for 14.175, erect it at least 20-feet off the ground and keep metal away from it (especially out of the "rectangle", you'll have a beautifully "flat"  response.  Of course, like any Yagi-derived design, your forward gain will be higher below the resonant frequency at the expense of F/B ratio and vice-versa, but I've found this antenna to perform well in both aspects throughout the band.

 


The performance of the Moxon, compared with a dipole, is amazing. With the antenna pointed eastward from my Washington, DC-area QTH, my usual CW signal reports from the UK and Europe are 599 and above. SSB is equally strong. Swinging westward, domestic reports are no less than 589 90% of the time.  On sideband, results are equally good again. And the offaxis signal rejection on reception is like that of a 3 or 4 element monobander. During this past weekend's sun-induced propagation disaster, I was one of only a half dozen stations heard nationwide by the Collins net control station in Dallas. (The usual number is about 30).  I was 20-over down there!  (By the way, I run "barefoot.")

I'm not sure of how well your quad spider would work as a spreader for the Moxon.  If it's metal, it could severely detune the antenna -- especially if it's mounted on a metal mast.  As I mentioned, experiments with my Moxon have shown it to be somewhat sensitive to metal near it. A 40 meter dipole within 3-feet of the side of the Moxon's driven element caused the SWR to rise to over 2:1 at its resonant frequency. The proximity effect actually lowered the resonant frequency from 14.225 to about 14.050 and probably screwed up its pattern quite a bit.  Then, too, the "square" configuration dictated by the quad spider would work, but the antenna wouldn't be a true Moxon and its F/B ratio would suffer greatly.

By the way, R.L. Cebik, the guy who really pioneered and perfected the Moxon design, says the most critical measurement to maintain in the antenna is the spacing between the ends of the driver and reflector elements.  Nothing else matters as much. He suggests that even making loops in the wire elements when attaching them to the driver/reflector spacers can compromise the performance -- since it effectively changes the apparent diameter of the wire at that point.

Anyway, have fun with your experiments. I'd like to make a Moxon to Moxon sked with you when you're done.

All the best and VY 73,

Craig Roberts
W3CRR
Silver Spring, MD

Note:  Craig has now perfected  a great design for a 20 meter MOXON.  Click HERE for photos and construction notes.

 

08/26/04

Hello all...

I was curious about the basic electrical design of the Moxon, and converted your construction dimensions to simpler wavelength fractions. In this way I could get a better minds eye view of the antenna as an electrical device.

 

My interest is to perhaps use a Moxon on 6 Meters for mountaintop contesting. While (by your gain figures) it will probably have a couple dB's less gain than the 2 element Cubical Quad I now use (2 elements at .12 wavelength spacing) it will be physically smaller and present a better overall mechanical configuration with my other beams on 2 Meters as well as 135, 70, and 23 centimeters.

 

Your "Performance" reports seem somewhat anecdotal. Has anyone built one of these for the VHF or UHF spectrum? This would of course be a way to obtain real gain figures in dBm.

 

73! de John "KF6GDJ"

(see response below)

08/26/04

John,

 

I have had a lot of fun and great success with the 6m Moxon. During my last camping trip over the July 4th holidays, I logged Portugal using 100w ssb with the antenna on a painter pole at 15 feet. The antenna is mechanically robust as it is constructed of 6063-T832 drawn aluminum tubing, structural aluminum channel, solid fiberglass rod insulators, polypropylene tubing clamps, and stainless steel U-bolts/hardware. Overall dimensions (centerline to centerline) are approximately 84.5" x 31.5" and the total weight is 8.5 pounds. As to the antenna's gain and other characteristics, I have no hard information other than what I have modeled in EZNEC and measured on my MFJ analyzer.

 

At 15 feet elevation, the horizontally polarized version has the following modeled specs at 50.5 MHz:

  • 11.06 dBi gain
  • 25.18 dB front to back
  • 18 degree take-off angle
  • SWR @ 50.5 MHz: 1.07:1, 48.8 +j3.3 ohms
  • SWR @ 50-51 MHz: < 1.25:1
At 30 feet elevation:
  • 11.58 dBi gain
  • 30.96 dB front to back
  • 10 degree take-off angle
  • SWR @ 50.5 MHz: 1.1:1, 54.2 +j2.9 ohms
  • SWR @ 50-51 MHz: < 1.3:1 
For more technical information, go to LB Cebik's site at http://www.cebik.com/6m.html. I think you will find this antenna to be great for portable use. So, in case you are interested, I am attaching the drawings & EZNEC files to this email. Please keep Don and the group informed of your progress should you decide to build one. Good Luck!

 

73,

Allen, KG4JJH

10/11/04
 

Hello,

 

I want to put a dual-fire 40M moxon in the attic, made of wire but I'm a whisker short on space. Traditional Moxon designs show that I need over 15 meters width - but I only have about 13. By the way, by "dual-fire", I mean feeding coax to both elements and switching them in the shack - this will give me some West and East gain (North-South attic).

 

To shorten the Moxon, I am firstly about to test out tomorrow morning a home-brew shortened di-pole, using a couple of home-brew coils I made up after dinner tonight. Once tuned for about 7.1 Mhz, I will make up a matching dipole and proceed to the attic to construct my Moxon.

 

Do you think I'm off at a tangent or will I get some results on this one? I'm worried about the dimensions too. I feel some experiementing might be in order.

 

So, rather than experiement blind, I thought I would share this with you and ask if anyone else had tried to "shorten" a Moxon in this fashion and what their results were..?.

 

I'll pop back in a few days.

 

Kind regards,

 
_____________________________________________

Callum McCormick

M0MCX
Birmingham, UK

callum@mccormick.uk.com

 

p.s.

I love detailing my projects by the way and have already taken pictures of the coils and stuff I'm using. Right now I'm just wondering whereabouts along the dipole I should mount them. I think about 66% sounds neat.

 

The below link leads to some pictures of my current project which is almost finished. With the CQWW contest coming up, I need some gain on 40, hence the Moxon "project" which sounds better than a straight forward 2 ele beam, particularly with the nulling properties.

 

http://www.mccormick.uk.com/towerproject/

 

10/11/04

The 'Dual Fire' concept that Callum refers to, I believe, is what I did with the 40 Meter Moxon in Boston. It is possible to electrically switch the 40 meter Moxon. You get rid of the reflector by making it into a driven element. Thus you have two driven elements in the Moxon rectangle. You set up a relay to feed either. The length of coax between the remote relay and the center of either driven element is cut so as to introduce the reactive component needed to lower the resonant frequency of the unfed element sufficiently so as to cause it to behave as a reflector. A tricky operation. Within an attic it is likely to not exhibit performance levels which would justify the effort of constructing and tuning it.

BILL W1ZY

bdesj@earthlink.net

10/12/04

During the last six months I have made three Moxon antenna's and following the formula exactly, all of them worked perfectly on completion, without any further adjustment.

They were made to operate on 2 meters, 4 meters, and 6 meters and each one has an SWR of 1:2:1 or 1:3:1. The first one was made for 4 meters, a band not available in the USA and on testing it I was astounded to find that the SWR was so low. I expected to have to make adjustments, but none were required. The biggest problem was having to find ways of fitting the
different sizes of aluminum tubes that I have to make the antenna and then find the appropriate Jubilee or circlip clips to hold the 3/4" and 5/8" tubes together and then fix it to a mast.  I was also able to adjust the antenna so that it could be used in the vertical or horizontal position.

After making it  and buying a small 4 meter FM rig I found that operators on the band were as rare as hens teeth so I sold the rig and the antenna to a fella who lived 900 ft.ASL.

The 6 meter Moxon has yet to be used, the only operator I have heard was a mobile who answered a call from an Italian station and their contact lasted about 45 seconds!  This antenna was made with 10 mm aluminum tube and the problem on this model was fitting the 1/4" aluminum rod for the corners into the 10 mm tubes and making a tight fit as there are no clips available which are small enough to do the job.  This was done by drilling the correct size hole into plastic washers that I made and then squeezing them over the slotted tube and the washers held the rod and the tube together very tightly.

The next project will be a Moxon for 10 meters but there is no rush to get started as the band will not be available for any decent DX until about 2008.

73,

Mel  G0GQK

11/06/04

Hello all..

There are some great variations of the moxon theme on the site, especially "Bills Baby" W1ZY `s 40mtr beast !

- well done guys.

My multi  MOXON was still going strong up till 12 months ago - it was a dreadful night - blowing a real hoolie as we say over here, the xyl and I were off to V44 the following day , so we decided to take the MOXON down, to cut a long story short a big gust of wind blew up and took us all to the ground !!! - guess what ?, the MOXON broke my fall - and YES !! - I broke the MOXON. - Boo Hoo !!!

Not to be deterred we licked our wounds in St.Kitts and I strung up a 20mtr "mini mox" to work QRP with my faithful FT817 ( Incidentally - there are some great guys over there - Carl V44NK - Terry V44KBP and Earl V44NEF were extremely helpful and hospitable).

Holiday over, it was back to the workshop in "G" land where we resurrected the remains of the "MULTI - MOX" but this time as a single bander for 20 mtrs, to try and evaluate the differences.

Obviously without a "reference" antenna it is a bit of a meaningless exercise - but I do have a good friend G0MUR who lives just down the way from me - he works the world on his G5RV and we have made many comparisons over the years, so he is my reference antenna.

Again with cycle conditions changing we can only be subjective - but yes - I think the single bander does have the edge. In the past 11 months the DXCC has risen 6 to 295 countries ( the latest being XX9,YV0D,FO/A,FO/M,V63 and V73), all having been "MOX`d".

DONT THINK IT - DO IT !!!.

Cheers to all and keep up the good work.

Phil G0WSP

11/09/04

Hi to all....

I am contemplating building a moxon like W3CCR's moxon (20 mtr), and also a 17 mtr moxon in the same fashion. Both will be on the same mast using the same rotor, but separate coax feedlines. I figure the 17 mtr moxon will be about 3-4 ft. above the 20 mtr moxon. Will I get any interaction or degraded performance from either, or should I install on two separate masts, say,75 ft. from each other?

  I wanted to get some input before I start building so my efforts aren't futile and waste valueble time before the snow flies here.

Thanks in advance. 

Paul  AD3G

(see two replies to Paul's question below)

11/09/04

Hi Paul,

You can safely stack the 20 and 17 meter Moxons. A four to five foot
separation should be sufficient.  Next week I'm delivering that very
combination and configuration to a ham radio dealer in Arkansas.

Good luck with your project. Let me know how it goes...and visit me at
www.aerialacts.com.

73,

Craig
W3CRR

11/10/04

Paul,

 

I have looked at stacking Moxons in an earlier attempt to get two or more bands on the same mast. 20/17m modeling results are listed below. In general, the antennas will become detuned when separated by 5 feet, especially for 17m. Also, the 17m gain is down 1 dBi and the f/b ratio is less than one half that of a monoband Moxon. If you can live with these numbers and tune both bands back into resonance you will have a working antenna, but not one that retains the monoband Moxon characteristics. 20/17m antennas vertically separated by 30 feet or more require no modifications to stack and come closer to monoband figures.

 

Until reading LB Cebik's article on Moxon Nesting I had problems multibanding the Moxon (http://www.cebik.com/mox1712.html). Cebik's advice is to skip a band when nesting (i.e. 10/15m, 12/17m, 15/20m, etc.). After many hours of EZNEC modeling I came away with a "buildable" dual band wire Moxon for 12/17m that retains the characteristics of the monoband version. Since then, I have successfully built and used the antenna with excellent results. The elements are at the same elevation with one common 50 ohm feed. A construction article was submitted to QST and will be published in the future.
 

I hope this answers some of your questions. Good Luck!

 

73,

Allen, KG4JJH

Stacking Moxon Rectangles

KG4JJH

 

 

1.       Moxgen generated elements (20m = 1.5 alum, 17m = 1 alum). EZNEC model for each antenna individually:

Band

Elevation

EZNEC Resonance

Gain @ resonance

F/B @ resonance

20m

50 ft.

14.15 MHz

10.98 dBi

20.18 dB

17m

55 ft.

18.118 MHz

11.42 dBi

27.85 dB

 

2.       EZNEC model for both antennas with 5 ft. separation:

Band

Elevation

EZNEC Resonance

Gain @ resonance

F/B @ resonance

20m

50 ft.

14.05 MHz

11.04 dBi

20.13 dB

17m

55 ft.

18.65 MHz

10.45 dBi

11.5 dB

 

3.       EZNEC model for both antennas with 20 ft. separation:

Band

Elevation

EZNEC Resonance

Gain @ resonance

F/B @ resonance

20m

50 ft.

14.15 MHz

10.82 dBi

16.61 dB

17m

70 ft.

18.108 MHz

11.99 dBi

29.78 dB

 

4.       EZNEC model for both antennas with 30 ft. separation:

Band

Elevation

EZNEC Resonance

Gain @ resonance

F/B @ resonance

20m

50 ft.

14.15 MHz

10.93 dBi

20.53 dB

17m

80 ft.

18.118 MHz

12.44 dBi

17.31 dB

 

Conclusions:

1.       Compared to monoband Moxons, at 5 ft. separation the resonance of the 20m Moxon shifts down 100 KHz, gain & F/B are OK. The resonance of the 17m Moxon shifts up 600 KHz, gain is down 1 dBi, & F/B is down 16.35 dB. If you can live with the reduced gain and F/B, change the dimensions of the both antennas to move resonance into the bands.  Multiply each dimension of the 20m Moxon by 0.99293, and each dimension of the 17m Moxon by 1.02936.

 

After this adjustment the EZNEC model for both antennas with 5 ft. separation looks like this:

Band

Elevation

EZNEC Resonance

Gain @ resonance

F/B @ resonance

20m

50 ft.

14.15 MHz

11.13 dBi

24.5 dB

17m

55 ft.

18.118 MHz

10.38 dBi

11.67 dB

 

2.       Mount the 17m Moxon 30 ft. higher than the 20m Moxon. 20m figures are the same as monobander. 17m gain is up 1.4 dBi (due to increased elevation) but f/b is down about 10 dB.

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