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THE
ONE ELEMENT V BEAM!
A PROJECT BY KB4XJ
A
ONE ELEMENT V BEAM FOR 15 METERS
"I refer to this as my ONE ELEMENT
BEAM, It's a horizontal Vee!"
IT OUTPERFORMED 2
ELEMENT BEAMS WE HAD ON 10 METERS AND 20 METERS IN LAST YEAR'S FIELD
DAY!
IT HAS GAIN IN A SINGLE
ELEMENT DESIGN! THE db GAIN, IF FIGURED BY THE BOOK,
IS 3db OVER A
DIPOLE!.".....DARRELL REF 1
In
log-periodic dipoles, it was found that forward tilt increased gain by
a 3 to 4 db over a regular log dipole.
REF2 Horizontal V Antenna for 15
Meters
"The HORIZONTAL V
ANTENNA FOR 15 METERS"
This often leds to
the question of what is a Beam Antenna. In it smallest of states, the
Horizontal Vee, must be one of the least researched or understood
antennas.
After stumbling on misleading data one would think the
antenna to be a dud, that efforts to make such a antenna would be a waste
of time.....
This is far from the case.....read
on......DARRELL.
A ONE ELEMENT "BEAM" FOR 15
METERS
CONSTRUCTION
DETAILS
In log-periodic dipoles it was found that forward tilt
increased gain by a 3 to 4 db over a regular log dipole. Ref 2
A little
history, 3 years ago, I was using a rotatable dipole for 15 Meters and had
good results but wanted something better. This dipole was built with a DAK
dipole mount and used 36 inch extenders with 6 foot 10 7/8 inch fiberglass
CB whip antennas. This worked well, but I wanted something a little
better. I spent more time reading about antennas and got interested in the
Horizontal V antenna and found that the basic V starts at 1/4 wave with a
90 degree angle. Ref 1
Time to build and
test my acquired knowledge.
The center of the antenna started
life as 2 mirror mount CB antenna mounting brackets,
Coax connection and mount
shown in the
picture above, the first piece was flat on both sides of 90 degree angle
and a second 5/8 inch hole was added an equal distance on the other
side.
The second mirror mount is heli-arced to the first piece, with
the top piece horizontal and the bottom piece vertical with the pole mount
going down. (See picture above) Welding was done at a local welding shop
for a $5 bill.
Now I use the insulated CB 3/8 by 24 antenna
mounting kits. You can pick these up at Radio Shack but get 2 and get the
ones with bolts and stay away from the flimsy
screws. The kits come with 2 bolts, 2 long nuts, and the plastic
insulators. Use one kit per 5/8 hole on top, going from back to front (
bolt, insulator, thru antenna bracket, insulator, long nut). Also while at
Radio Shack pickup a couple of heavy duty terminal ends for the end of
your coax. The coax is done in a pigtail fashion and connected on the bolt
side of the antenna insulator hole 3/8 dia with at least a #10 wire
connector for your terminal ends.
Extender Elements
Extender Elements
My
elements consist of two 6 foot 10 7/8 inch fiberglass CB whip antennas
with 38 inch extenders.(See picture above) and note that the original
dipole used 36 inch but do to the induction between the elements,
the resonant frequency raised to 21.350 MHZ. The 38 inch extenders
lower the frequency to 21.250 with a l to 1 SWR. I operated field day on
21.205 and only got chased off frequency twice and came back and retook
the frequency, minutes later.
Extender drawing above by John Butler, Planet Productions Dallas,
Texas
The extenders were made from 1/2 inch EMT tubing. On one
end a 3/8 by 24 long nut is inserted leaving 1/16 inch exposed for
soldering. Soldering was done with a 5% silver solder. On the other end a
3/8 by 24 bolt, 1 1/2 inch long, with a 3/8 by 24 nut attached to leave
1/2 inch of threads exposed was inserted in the other end leaving 1/16 of
the nut exposed and the 1/2 inch of threads.
The nut is soldered on
the exposed 1/16 inch of nut, take care not to weld on the exposed 1/2 of
treads. Arrows in drawing indicate weld points. Two of these must be
made.
Final Assembly and
Performance!
The final assembly starts at the center antenna
mount. (See Picture above)
Connect coax pigtail on bolt side of
antenna center insulators, connect treaded side extender to center,
connect whip to extender and repeat for the other side. (See picture
above)
The entire 15 Meter antenna weights around 6 pounds and was
used on a 20 foot tower with an 18 inch truck wheel for a base, no guy
wires were used and it withstood a 30 mile per hour wind when a
thunderstorm hit just after setup for field day 2001. It has performed
better then I could ever have imagined. I learned what it was like to be
in a pileup and have fun, we even worked DX and had 49 of 50 states in the
24 hour period! We had directivity, and rotating from NE to NW we lost the
DX, but started working the Western States. I figure the gain over a
vertical at around 6 db, and a walk around the Horizontal V with a field
strength meter, (see diagram below), was enough to tell me that this antenna will perform. A fellow ham
came by, Gordon Blauser, and I let Gordon walk around with the field
strength meter and he walked away amazed with how good the
antenna performed with 10 watts running to it. He got one of the prototype
centers and was vowing to try using 2 hamsticks on his
V.
I also have to get Spencer Whitmire, W4ERC's
report on how another prototype center is being tested on 6 Meter
with just a couple of stainless steal whips cut down to around 52 inches
that will work on the Magic Band. The center antenna mount could be made
with a 6 or 8 inch longpiece of aluminum angle 2 inch by 2 inch and 1/4
inch thick. This should give plenty of space for the mast clamp.
Nay
sayers may say that the aluminum mast affected the radiation pattern but
it worked for the good of the antenna.
Using the 36 inch &
38 inch extenders together with the whips puts the antenna on 17
Meters.
Previous experiments with a different length whip on the 36
inch extenders enabled operation on 12 Meters.
I lost this bit of
research and suppose that with adjustable extenders, (which I haven't
designed yet), would do the trick of getting multi-band coverage, but
below 20 Meters the antenna would lose the ability of 1 man erection.
Remember this antenna is directive and is rotated when used in
the
field and is done by the arm strong method, and if guyed, use
guy wires on a slip ring.
FOOTNOTES ADDED BY DARREL.....
KB4XJ
The dipole formula of 468/freq will work but, an
extra 2 inches must be added to the final result.The induction
between the elements changes the resonant frequency of the antenna, and
with a dipole cut for 21.250 Mhz (SWR 1:!) when folded into the V
shape, the induction of the elements moves the freqency UP to 21.350 Mhz
(SWR 1:1). The Basic principle of the V antenna, when dealing with the rf
radiation lobes are that the lobes in the bisector of the V tend to add
and the other lobes tend to cancel.
I'am President of the Local Ham
Radio Club, and the chairman of the upcoming Field Day 2002. My 20
Meter operator has vowed revenge for the beating he got in last years
Field Day from the One Element Beam and has stated that he's going to give
me a run for the money and has bought a NEW antenna which will replace his
2 element butterfly beam.
I accepted his challenge and told him I
would be using my V and that I wanted his competition AND that I wasn't
going to roll over and give up just because he got a new
antenna.
The proto-type 6 Meter Horizontal V will be used by
Spencer Whitmire W4ERC, the Vice President of the local radio club,
Spencer was on 10 Meters with a 2 element beam and was converted to a
believer when he saw the V in operation in last year's field
day.
Spencer will give 6 Meters a try with the V.
Our callsign for
Field Day 2002 was K4W (Kilo Four Whiskey).
I became an
EXTRA in 12-4-98. The One Element Beam is the results of several years of
work on various antennas, I was really depressed with the results of tests
on so called big signal antennas and finally went back to the horizontal
dipole with good reports. I remembered from my beginning in ham radio
about the inverted V that I used on 75 Meters and how I could get into
Hawaii. I also remembered that an inverted V could be made directive
by the leg angle. This was the turning point which led to the ONE
ELEMENT BEAM. While reviewing the logs of last years field day, I found
KH6, VE6, VE3, VE4, VE5, KP4, VE7, NP2, DJ2, NP4, TZ6, GO6, VE1, VE9, XE1,
RX3, DL6, EA4, OH4, G4, G0, EA5, EA3, DL1, OH1, RA3, DJ2, F6, PA3, F5, F6,
AND VE2. I found these prefixs in the log book of the DX worked during
field day, with the Horizontal V.
Antenna shown broken down for field day.
Notice
truck wheel used for base
Top view radiation pattern
"Estimate"
with a field strength meter yields a 2 to 1 ratio
off the front
THIS IS THE BEST PERFORMING
ANTENNA I HAVE EVER BUILT!
DON'T LET THE SIZE FOOL YOU.
All
that is required to use this antenna is a willingness to give it a try and
then look at the results.
It then comes down to operator skill as to
how many contacts you can do per minute.
It truly is AMAZING! Darrell
Koranda KB4XJ
E-Mail
address kb4xj@strato.net
Reference 1 The ARRL Antenna Book 1994, page 13-2
(chart gain of single long wire over a dipole\O-db ), page 13-5
(2 long wires placed in Horizontal V, give a 3 db gain over chart on
page 13-2)
Reference 2
The ARRL Antenna
Book 1994, page 10-20
(forward tilt of elements, gain increase of 4
db) log-periodic V array as compared to
log-dipole
20 THRU 6 METER VERSION
BY
LA0HV OF
NORWAY
CLICK HERE!
Editors note: Please give credit to
KB4XJ for this fantastic project!
"Many thanks to Darrell for
all his efforts, hard work and DEDICATION TO HAM RADIO
while getting
this great project up and running for all hams to enjoy!"
N4UJW
HAMUNIVERSE.COM
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