The N5WVX 2 Meter 7 Element Yagi with a
"Twist"
( Cool Elements)
Based on the 2 Meter Beam Project by
Larry Morgan, AG5Z
It's hot weather in Texas in
July and Larry Parker, N5WVX, shows us a novel way to
make these "cool" elements for a 2 meter Yagi and also his
method of building a gamma match. This antenna was designed for the
low end of 2 meters and Larry shares his fun with it with everyone
who loves homebrewing antennas. Here is a "Cool" 2 meter Yagi designed to
give you lots of fun on these hot summer days. Grab a glass of iced
tea.....with a "Twist".
We call Larry's 2 meter Yagi
project.... A Yagi with a "Twist".
Lemon anyone! (Hot chocolate can be used in the winter...hold the
lemon!)
See the "Twist" above? Cool!
You will notice in the closeup above
that the element is twisted.
It is made from #10 SOLID copper wire that
is twisted. If you don't have ready access to tubing for small Yagi
elements and have plenty of #10 wire laying around, then try Larry's
method of making the elements for a Yagi. Read on to learn how he does
it.
Material needed
1. 12 PIECES OF 10 GAUGE
COPPER WIRE 48" LONG BECAUSE WHEN YOU TWIST IT TOGETHER IT
SHRINKS>>> IF YOU PLACE THE TWO WIRES TOGETHER AND PLACE THE END
IN A VICE AND USE A DRILL, YOU CAN TWIST THE WIRE INTO A SPIRAL.
TRIM
FINAL LENGTHS AS NEEDED FOR EACH ELEMENT AND MOUNT TO
BOOM.
USE CAUTION WHEN USING A DRILL TO
MAKE THE TWISTS! A GOOD PAIR OF SAFETY GLASSES SHOULD BE USED IN CASE THE
WIRE COMES OUT OF THE VICE WHEN TWISTING...USE A VARIABLE SPEED DRILL AND
BE CAREFUL!
IF YOU
PREFER, USE A SCREWDRIVER OR OTHER METHOD TO GET THE
TWISTS!
2. 3/8 " COPPER TUBING 1 1/2 FT
LONG..THEN FLATTEN TUBING TO BE CUT AT LEAST 1 1/2" LONG EACH. THIS WILL
BE USED TO SOLDER OVER THE ELEMENTS WHEN ATTACHING TO THE BOOM. SEE
PICTURE ABOVE.
A SHORT COPPER STRIP CAN BE USED AS A STRAP ACROSS THE
ELEMENTS FOR SUPPORT AND SCREWED TO THE BOOM AS IN PICTURE ABOVE.
NOTICE THAT EVERYTHING IS SOLDERED WELL.
3. YOU NEED 12 OR MORE SHEET
METAL SCREWS. USE TWO ON EACH ELEMENT AS SHOWN IN PICTURE
ABOVE.
4. GAMMA MATCH--YOU NEED PIECE OF
3/8" ALUMINUM TUBING 5 1/2" LONG.
FLATTEN ONE END 1/2". THE
EASIEST WAY IS TO PUT IT IN A VICE & SQUEEZE.
TAKE A PIECE OF COAX 9913..... STRIP
OUTSIDE SHIELD OFF BUT LEAVE PLASTIC INSULATION ON CONDUCTOR WIRE.
IT SHOULD BE 7-8"LONG.. WHEN YOU STRIP WIRE LEAVE AT LEAST 5"
OF INSULATION ON AND STRIP THE REST.
Drawing of standard
gamma match and Larry's version below
it:
(Typical
gamma match above)
Larry's Gamma Match
construction
In Larry's version, he inverted the
gamma match both electrically and physically as shown in the pictures
below showing the sequence of construction.
Materials layed out for use.
All
lengths have been cut to final lengths. The SO-239 has been mounted in a
small "L" bracket made from aluminum with the appropriate hole
drilled out and secured with short bolts and nuts. Note the black
insulation over the conductor. This, along with the center conductor
of the coax, forms a tuning capacitor when inserted inside the tubing
below it in the picture. You will also see a small adjustable copper
bracket which doubles as a spacer and support that has already been
bent to fit the coax center conductor and the 3/8 inch tubing. The idea
here is to make it where it will slide for SWR adjustment later and then
can be securely tightened on the driven element end and the gamma
tubing.
Step 1. "L" bracket mounted
to driven element with a bolt of proper length.
You should also notice the very long bolt extending thru the driven
element.
This bolt is used to mount the driven element to the
boom.
Cut off any excess length after mounting on boom.
The
bolt length will depend on the diameter of your
boom.
Step 2. 3/8 inch tubing with flattened
end mounted to center pin of SO-239. It is difficult to see in the
picture, but a hole is drilled in the end of the flattened portion of the
tubing and a screw or small bolt was used for the mounting. Don't
over tighten. The end result is that the tubing is
insulated from the outer shell of the
SO-239 by mounting it on the center pin.
The spacing between the gamma
match assembly and the driven element should be about 1 1/2
inches after completion.
Step 3. Showing the insertion of
the coax assembly inside the tubing.
Also note the wedding ring on the
left hand and the pin and pad nearby.
The pad is used for "excuses"
for the XYL as to why he is not mowing the yard.
Larry will have
a page full of excuses when he is done!
The antenna should work fine,
but will the excuses?
Step 4. Final assembly of gamma match mounted to the driven element!
Larry has gone for some
lemon for his iced tea! That list of excuses is
growing!
You can use the gamma
match mounted either on the top or bottom of the boom. Your choice.
See picture below.
GAMMA MATCH 5 1/2 " LONG 1 1/2 " SPACING
FROM DRIVEN ELEMENT.
Tune by sliding the coax inside the tube and
adjusting the sliding clamp back or forward toward the boom for lowest
SWR. The two will interact so when you tune one for lowest SWR, then tune
the other adjustment.
You will eventually reach the lowest
setting.
Finished antenna in the
air!
Note - Picture above shows 7 "twisted"
directors and the driven element with the reflector out of frame on a
9 element version. You can use as many directors as you want, but maintain
the 16 inch spacing and decrease the length of each successive director by
1/8 inch.
Larry used a length of tubing for the driven element in the
picture above for more stability with the gamma match attached.
(7 Element version not drawn to
scale)
Note: All lengths are in
inches
1ST ELEMENT, THE
REFLECTOR ON LEFT IN DRAWING ABOVE, IS 40",
2ND
ELEMENT 37 7/8" (The driven element) DE
3RD ELEMENT 36,
D1
4TH ELEMENT 35 7/8 D2
5TH ELEMENT 35 3/4 D3
6TH ELEMENT 35 5/8
D4
7TH ELEMENT 35 1/2 D5
SPACING IS 16" BETWEEN EACH
ONE
Final SWR reading were:
SWR 1.2 ON 144.200-145.600
Running the lengths and
spacing using the Quick Yagi Program by WA7RAI yielded these results based
on an element diameter of about 1/4 inch.....
Gain - 11.66 dbi (thats
about 9 dbd gain)
F/B ratio - 17.00
Editor's note:
There are many ways to put together a
Yagi. There are also many ways to use different types of materials such as
hollow aluminum tubing, solid aluminum tubing, and also wire supported on
wooden dowels, fiberglass rods, even small diameter PVC, etc for the
elements and to build a gamma match.
This article and project shows 2
different ways of building and attaching a gamma match...it is your choice
to choose which is best for your building experience...either will work
just as well as the other. Use your own ingenuity and "ham engineering"
to make one work for you. Larry has shown us a cool way to make the
elements with wire and much stronger than just using one single wire and
his method works for him. Now it's your turn....get building and
experiment! 73 N5WVX, Larry!
Email Larry here for
questions ~~~~~ larry_969 (at) hotmail.com
Note: This
is a spam fighting email address above. Make sure you reinsert the @ sign
in the appropriate place in his email address.
Many thanks to Larry, N5WVX for
sharing his "cool" ideas with us!
N4UJW
