Background and Motivation:
(What is presented here is derivative work of Alex (IBCrazy). It
is based on this
article on RC Groups
Cloverleaf antennas are a circularly polarized omni-directional antenna
commonly used for FPV (First Person View) piloting of RC(Radio
Controlled) Aircraft (Also called Video Piloting). Cloverleaf
antennas significantly out-perform linearly polarized antennas in cases
where the relative orientation of the transmitting antenna and the
receiving antenna is changing, and when used at frequencies where
multi-pathing becomes problematic. Both of these conditions exist
with modern FPV flying. While references to similar circular
polarized, omni directional antennas where described in Ham Radio and
Communications publications many years ago, their recent resurgence and
use in FPV applications is credited to Alex (IBCrazy). Alex
provided a DIY (Do It Yourself) tutorial on the aforementioned RC
I originally made several cloverleaf antennas based on Alex's original
instructions. While testing proved the antennas out-performed whip
antennas, I found it impossible for me to make professional-looking
I needed a way to help me make better cloverleaf antennas.
In an effort to improve symmetry, I attempted to make them using 3
separate lobes instead of the 2 and 1 method Alex originally described.
This did produce an antenna that was more symmetrical, but it was very
difficult to hold the 3 lobes while soldering. If I
attempted to reheat them, the whole thing would fall apart. I
needed some sort of jig or holder. I had several ideas - a
"helping hands" like device with several extra arms - Too awkward and
expensive. A wood jig - Would take too long to make. Then I
realized that all I needed was a flat surface that would clamp the
bottom (horizontal) part of each lobe. I had my solution - It would be cheap,
and quick enough to build for my impatience.
The device as described is for making 5.8GHz antennas, but 2.4 or 1.3
GHz antennas can be made with the same device.
The device described is for 3 lobed cloverleafs. Obviously,
one can be made for making 4 lobed Skew Planar Wheels (WW4SSII).
Back to Contents
This article describes building antennas that can be connected
to either a transmitter or a receiver. While a faulty antenna cannot
damage a receiver, it can permanently damage your video transmitter.
The type of antenna described here was not designed by the author of
this document. The author is not attesting to the suitably of
such an antenna for any application, or its suitability for use with
any particular transmitter. Responsibility for the
construction and use of described antennas is solely the responsibility
of the reader/builder.
Certain operations described here involve potential
hazards, and require the use of proper workshop practice and personal protective
equipment (PPE). Readers not familiar with proper workshop practices,
and thus the type and use of PPE, must learn those things prior to
attempting to perform the work described here.
This describes a method for those who have already decided to take on
the challenge and receive the satisfaction of making their own
antennas. I am not suggesting or advocating making your own
antennas in leu of purchasing genuine IBCrazy commercially produced
I do, however recommend one of those 2 options over purchasing antennas
of unknown pedigree. See above about possible transmitter
damage. If you buy a poor quality cloverleaf or "mushroom
antenna", you will loose your money, and you may loose a transmitter,
or possibly a whole aircraft. You will gain nothing. "Learning"
that a certain vendor ripped you off is not really learning. If you build
the WW3SSII, and use it to make your own antenna,
even if the worst happens, and you loose a transmitter or
aircraft, at least you have gained skill and experience.
Back to Contents
Making the WW3SSII Device:
Obtain a large "Fender" washer. The one shown here has an outside
diameter of 1.25 inches (about 32mm). Make sure that an SMA
connector will easily pass through the center of the washer, otherwise
you can't get the WW3SSII device off of the completed antenna (which is
embarrassing.) Use regular grade steel, not copper or aluminum,
grade 8, stainless, etc.
(Why plain steel? - Copper or Aluminum are too good a conductor of
heat. Despite the wire (lobe) being clamped into the WW3SSII,
soldering the antenna is no problem when steel is used. Also,
softer materials will not hold the threads as well. Harder
materials are simply more difficult to drill and thread
We must now mark a line every 120 degrees. This can be done with
a protractor, but I simply placed the washer on a printed diagram of a
circle with 120 degree lines. It can also be done by drawing
equal lateral triangles. It doesn't matter how you do it, so long
as you can mark the washer every 120 degrees.
Next, center punch the washer on each line, and approximately 6 - 7mm
from the center point of the circle (The one pictured is my first
prototype, and the screws are slightly too far out for optimal use
building a 5.8GHz antenna, but it works). Where this is on the
washer will depend on the washer you use. It needs to be near the
center of the horizontal part of a 5.8GHz antenna. Even if you
build larger antennas, make the jig for 5.8GHz.
Drill holes the proper size for the tap you will use. I used 6 -
32 screws, so that is a number 32 drill. Do not clean out the hole.
We need all the material we can get to hold the threads.
A finer thread will mean more threads in a given thickness of material.
Using the correct tap, thread the holes. Once the holes are
threaded, you can remove any sharp bits with a file.
We now need to make the channels for the wire to sit in. They are
tangent to the holes, and should be straight from the inside to the
outside. You don't really need to re-measure. As long as
the screw holes are pretty close to 120 degrees, and you keep the
channels on the proper side of each screw, they should remain pretty
close to 120 degrees.
Using a Rotary tool with
a thin cut-off wheel, make the slots. I use 0.030in welding wire to
make my 5.8GHz cloverleafs, so the channels should be about 0.010in deep.
Install the washers and screws. I used what I believe are PC Hard
drive mounting screws. Optionally, peen the ends of the
screws or purposely damage (bugger) the last couple threads so that the
screws won't fall out.
(Optional - apply Teflon tape (as used in plumbing) to the screw
threads. This holds the loose screws in the threads, and allows
them to be lightly tightened while positioning the lobes.
Back to Contents
the WW3SSII Device to Make an Antenna:
The reader is encouraged to read the first several posts of the referenced
RC Groups thread
to become familiar with cloverleaf antennas and
their construction before proceeding.
Obtain some 0.025 - 0.035in dia. solid welding wire. (You will also need
a length of appropriate coax cable, or a coax assembly as shown in the
RC Groups thread.) Do not use flux core welding wire. As per the
instructions in the RC Groups thread, cut 3 of the short wires only
will not make the long wire. For 5.8GHz, the wire is 53 mm long.
Bend each wire 13 mm from each end to form a long, square "U".
Next, work along the center span, bending it into a uniform curve until
the ends of the wire meet. They will not/should not make a 90
degree angle. Work/rework the curve until it is smooth and
uniform, and the lobe can lay flat.
Holding the wire with the curve right, and one end horizontal as
shown, bend the wire slightly so that the end of the top wire
(which should be pointing down) is slightly (about 2 mm) closer to you
than the end of the horizontal wire. (Right Hand Circular
Polarization - RHCP. Bend away from you for LHCP.)
Make 2 more identical lobes.
Insert the horizontal wire of a lobe under one of the washers.
Lightly tighten the screw so that the lobe can be both pivoted,and
moved latterly. With the WW3SSII oriented so that the lobe is toward
your right (as shown), angle that lobe away from you at a 45 degree
angle (for RHCP). In other words, the plane of the lobe should be
approximately perpendicular to a line pointing at your face. You
can use a 45 degree wedge cut from paper or other material, or you can
achieve good enough results just by "eye-balling" it.
Rotate the WW3SSII clockwise 120 degrees (viewed from above),
insert the next lobe, and align in a similar manner. Repeat for
the third lobe.
If you are using a center collar or ground plane/balun, insert it
now. Move the lobes laterally as needed to put the horizontal
ends into the holes (Making a balun is not described here). If
not, move the lobes so that the horizontal leads meet in the
middle. Bend the end of the wires slightly if needed to make them
Do a final alignment of all 3 lobes. Loosen or tighten the screws
as needed to allow for alignment. Without disturbing the adjacent lobe,
tighten each screw enough to hold the lobe. There are not a lot
of threads there. Do not tighten so much that you damage the them.
Carefully examine the alignment and tweek as necessary.
Put the WW3SSII assembly in a small hobby vise or
helping hands, and solder the lower (ground) lobe ends.
Gently bend (not pivot) the lobes as needed so that the upper ends meet
about 2 mm above the lower intersection. The leads should just touch
without being under stress. If you think you might have stressed the
lower solder joint, re-flow it.
Insert the coax cable from the bottom, mark it so that the top
connection will connect to the center conductor and the bottom connects
to the shield. Remove the coax, and carefully strip it.
Re-insert, and solder the lower antenna point to the shield. If
nothing was under stress, and the screws were tight enough, nothing
should move when you re-heat it to solder the coax.
(Optional - At this point, with the
bottom (shield) soldered, and the center conductor not touching anything, you
can do an optional check. Use a MultiMeter in continuity or
resistance mode to test between the shield and center conductor.
At this point you should *not* have continuity. If you do,
either the coax assembly was bad, (i.e. connector was installed
improperly), or you overheated the coax while soldering the
If there is not continuity, solder the top antenna connection to the
center coax conductor. Again, thanks to the WW3SSII, you
should be able to do this without anything moving.
Make sure you do not solder bridge the top and
bottom. The distance between the top and bottom connections is
important. You do not want them to touch (obviously). You
also do not want them so close that they form a tiny capacitor.
At 5.8GHz even a very tiny capacitance means a significant
impedance. Similarly, too much distance distorts the antenna, and
changes it's tuning. Keep the distance about 1 - 2mm. The one
shown has a copper ground plane or balun, and the gap between the
top connection, and the bottom is larger than it would be ideally.
Let it cool, and remove it from the WW3SSII device.
Cover the connection areas with hot glue, silicone or epoxy. Do not use
epoxy that contains metallic substances.
Always do a ground range test before
WW3SSII can also be used to re-from or repair a crash (or otherwise)
damaged cloverleaf antenna. Remove any glue/covering as needed.
Lower the antenna into the WW3SSII with the lobes between the
screws. Loosen the screws, and rotate the antenna so that the
lobes go into the slots. If the lower part of a lobe is bent or
detached, leave that screw loose. Tighten the screw of each good
lobe. Clamp the WW3SSII, and reshape the antenna as needed using
2 needle nose pliers. While care must still be used so that none of the
good solder connections are stressed or torqued, the WW3SSII device
will help maintain alignment, and prevent further damage. Resolder as
Back to Contents
Please discuss this
article on the Linuxslate.com Forums.
Forums for this device
THIS DOCUMENT IS
PROVIDED BY THE AUTHOR "AS IS". IN
SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
ARISING IN ANY WAY OUT OF THE USE
OF THIS DOCUMENT, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
trademarks/tradenames and images are
the property of the companies
that own them.
Images copyright (c) 2014 linuxslate.com