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THE HENTENNA
RE-VISITED
"The following article has been
re-edited for the English language from the Japanese site.
Minor
errors and corrections have been made."
The Hentenna
was developed by Japanese 6 Meter Hams, JE1DEU / JH1FCZ/ JH1YST in the
1970's and can be designed and built for hf thru uhf and possibly
beyond!
After much experimentation, finally, the antenna
was developed with good performance, however, it was difficult to explain
why the performance was so good, or how it is worked basically at that
time. So it was named Hentenna ,
"Hen" means "strange" in Japanese.
The antenna has good performance and many advantages
and it has become very popular in Japan. Many JA stations make it
and enjoy it at home or in the field. Some Japanese 6m beacon stations are
using the Hentenna antenna.
HERE ARE
SOME GOOD POINTS FOR THE HENTENNA
1. Good
performance
2.5-3 dBd
gain
Low angle radiation
* Total performance is
equivalent to 2-3 element Yagi-uda antenna,
Wide band width
2. Easy to make
It is possible to adjust impedance and SWR perfectly, This means,
not so difficult to make!
No special parts are required. You can use
any electrical conductor to make the main
rectangle.
Broad adjustment ....wide bandwidth
3.
Easy
to build up
If you use thin aluminum
pipe and thin wire, you can make this antenna for 6m very light. It can be
designed for most any band or frequency by using the included
formulas below.
Due to it's construction, it is easy to put it in a
higher position in the air. You can also use light mast for it.
As
this is a vertically long antenna, it is easy to install the antenna on a
veranda or small space.
It appears to be a vertical antenna but has
mainly Horizontal
radiation:
This is one of the reasons this antenna is
"Hen",(STRANGE)
 
This antenna is shown in drawings above horizontally
polarized....
lay it on it's side for vertical polarization.
Also
please note in the above English drawings that the Hentenna is basically a
loop fed about 1/10 wavelength from the bottom element with 50 or 75 ohm
coax attached to the top element of the bottom loop at the center
point.
Hentenna Basics
1. Basically 1
1/3 WL Loop antenna around outer edge of
antenna
2. L1 works as 1 loop antenna
3. L2 works as
matching section
4. Vertical long rectangle has more gain than
ordinary square loop and has less impedance.
L2 helps the matching and
low angle radiation.
5. 3D pattern is like shell of peanut
(maximum gain directions looking at you and away from you) so it will be
somewhat bi-directional.
How to Adjust
1. Move the
"a" and "b" points to adjust swr. (move in equal amounts), move
towards top (in the drawing) to increase resonant frequency,
move
towards bottom to decrease resonant frequency.
2. SWR may be
higher than 1:1.5 at first so move matching points "a" and "b" in small
increments up or down the loop until lowest swr is obtained and secure at
these points with whatever method you choose depending on your
construction materials. The overall outside (total) length may have
to adjusted a small amount also.
The construction
materials you use for the loop will determine how the antenna is
supported.
It will weigh more if made from aluminum or copper
tube.
It will require a non conductive support mast or structure
to attach it even if made from wire. Nylon cord or rope, heavy
string or other non conductive material can be used for support at
the four corners.
A length of pvc pipe, plexiglass, wooden
dowels, etc can be used as support for the top, bottom and coax feed
point elements with the side wires strung between them or can be used to
completly enclose the wire.
Use your own design.
Most JA hams use
wire construction.
The
final configeration in the air should be as close to a vertical rectangle
as possible.
This antenna is shown in
drawings above horizontally polarized....lay it on it's side for vertical
polarization.
Experiment with your favorite support and try to
keep conductor size under 1/4 inch. See the Japan site link below for more
info.
+++++++++++++++++++++++++++++++++
6 Meter Version
THE MATH
Calculating the
lengths for the Hentenna is simple and straightforward and can be used for
HF THRU UHF and possibly beyond.
The
formulas below will get you in the ball park for most any band or
frequency. There are two methods for getting the approximate lengths.
Chose the one that works best for your math
abilities.
First
method formulas:
Just start with 1 meter = 39.36 inches
1
inch = 2.54 cm
1 wavelength = 6 meters = 6 x 39.36 =
236.16 inches
(Remember, this is not a 1 wavelength loop! It is 1 1/3
wavelength)
1/2 wavelength per side = 3 x 39.36 =118.08 inches
1/6
wavelength = 6/6 =1 wavelength = 39.36 inches
1/10 wavelength = 236.16
x .1 = 23.61 inches
Second
method formulas (The easiest)
These formulas were extrapolated from the Japaneese
plans and should yield lengths that are a bit long for easier final
tuning.
15744 / Freqmhz = total outside
length in inches of the "rectangle"
5904 / Freqmhz = 1/2 wavelength in
inches
1968 / /Freqmhz = 1/6 wavelength in inches
1180 / Freqmhz =
1/10 wavelength matching section
feedpoints
Using these formulas in
an example for 146mhz center frequency:
15744 / 146 = 107.83 inches total
conductor length (1 1/3 wavelength)
5904 / 146 = 40.43
inches (1/2 wavelength sides each)
1968 / 146 = 13.47 inches
(1/6 wavelength in inches) (top and bottom length as in drawing
above)
1180 / 146 = 8.08 inches (1/10 wavelength for matching
section feedpoint distance from bottom of antenna.) (Coax feed point
distance from bottom)
Some adjustment of lengths may be required
for peaking at design frequency. Experiment!
From the above method calculations we arrive at the lengths
for the 6 Meter Hentenna:
1/2 wavelength sides = 118.08
inches each
1/6 wavelength top, bottom and coax connection element =
39.36 inches
1/10 wavelength matching point = 23.61 inches up from each
side of bottom element.
The 2 Meter example
yields these lengths:
40.43 inches (1/2 wavelength
sides each)
13.47 inches (1/6 wavelength
in inches) (top and bottom length as in drawing
above)
8.08 inches (1/10 wavelength
for matching section feedpoint distance from bottom of antenna.) (Coax
feed point distance from bottom)
Total distance around the
rectangle = 107.83 inches.
Again, take notice that this is not just a full wave
loop!
At 6 meters, the total length around the outside of it is
314.88 inches which comes out to be 1 1/3 wavelength
long.
AT first glance the above measurements make this 6 meter antenna
to be HUGE! IT IS
NOT . It
is only about 9.8 feet tall by 3.28 feet wide!
A scaled down Hentenna
for 2 meters would be 1/3 it's size or about 39 inches by 13
inches!
EXPERIMENT!
EXPERIMENT!
Editors comments:
" I personally have not
built this antenna YET and cannot judge it's performance....make sure
you use low power when adjusting the swr and send me any comments you
desire about this "strange" Hentenna.
IF YOU HAVE EXPERIENCE WITH THIS ANTENNA AND HAVE ANYTHING TO ADD,
PLEASE LET ME KNOW."
N4UJW
Make sure to see the WA0IPT 2 METER VERSION
below:
Click the picture to see it or here 
Flash! Just added....6 Meter Hentenna by
K5USS here
More
on the Hentenna with length table at bottom of page here
CLICK HERE TO SEE
THE SITE FROM JAPAN FROM TAKA, JR1LZK
AND BE SURE TO NOTE ANY
TRANSLATION ERRORS!
Copyright 2000 - 2007 N4UJW
Hamuniverse.com and or article author
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