THE G4ZU....SPIDER BEAM......SKYPPER
elements wire Yagi comes along in a great variety of names. On the 11
meter we call it the Skypper due to the manufacturer Alex 1SD019
On Ham bands we call it the Spider beam or G4ZU.
What ever the name is its principle remains the same. It is a full-size
3 elements Yagi with the Director and Reflector bend towards the radiating
With this comes a small size Yagi with Gain 7,3 dBI and Front to Back
in the order of 30 dB
It is easy to build, with the materials in front of me I had the first
SWR test within an hour. And provided a great match within the 700 Khz
This is one antenna i will not get ride of...always handy for DX-expedition,
Holiday or Back-up for home
4 X fiberglass
Teflon wire about 5 meters
Electrical wire 15 meter
2 X U bolt
1 meter aluminum tube (80cm)
small aluminum plate about 5 centimeters long 2 centimeters wide
I used are fishermen tubes, each of a length of 4 meter lengths. You
will need only about 2,5 meter of the fishing rod but the lower part
of it is stronger therefore the antenna will stand through have wind.
It is easy possible to make the framework from other materials, I have
seen models made from bamboo as well.
used, originally wash line Teflon...4 mm, but any NON-guiding wire is
usable (perhaps from sailing boats that's extra strong)
The Electrical wire:
Any plain black and red 12 volt wire, or other form of electric guiding
wire is good..(example: loud speaker wire )
The U bolts we find on any old 27 mhz antenna are fine. You can also
buy them at the local hardware store. Just make sure it fits the mast
the beam is supposed to go on.
The 1 meter aluminum tube has either fit INTO or AROUND the fiberglass
poles in such a way that there is not to much friction.
Cut the aluminum tube in 2 pieces of 50 centimeter or 40 centimeter...no
- drill 2 holes close to the center of each tube. The sizes need to
be large enough for the U-bolts ( see picture below)
OF THE FRAMEWORK:
The first thing you should do now is put the U bolts though the aluminum
tubes and connect the aluminum tubes to a mast. Make sure you have about
30 centimeter of mast left above these aluminum tubes.
Connect the tubes above each other with 90 degrees difference. as shown
in the picture
Connect the 4 fishing rods to each open end of the aluminum tube. Now
looked from above you should see a cross.
MAKING OF THE ELEMENTS.:
Cut the electrical wires in pieces of : 5,25 meters (the reflector)
5,04 meters (the radiator)
4,84 meters (the director)
Take the reflector and put in the center of the reflector a little tape.
This will help you determine the center of the reflector later.
The same counts for the director.
Take the radiator and cut it in half. You now have two pieces of 2,52
meter. uncover the sealing from both wires at one side for about half
Solder the uncovered electrical wires. Each independent. And enter them
in the block-connector. This is your access for the coax. There are
many more ways to attach the coax cable on it but this is about the
What I did was take a small aluminum plate drill holes through it and
used that for braking the tension.
PUTTING IT TOGETHER:
Attach the radiator on the mast about 30 centimeters above the aluminum
Connect the Teflon wire (about 2x 50 centimeter) to the radiating dipole
at both ends the knobs you can use for that are as follows:
This knob will tighten itself when tension is brought on it.
Attach the Teflon wires to the fishing rods they should be in a bowl
Attach the other fishing rods...
Bend the fishing rods upwards and measure 2,5 meters from the Block-Connector.
Put a tape around both fishing rods at that point. (this will be approx
Connect the Reflector (tape on tape) on a fishing rod. And connect the
Director on a fishing rod. (again tape to tape)
You could connect them with either wire or T-reps.
Bring the Teflon wires towards the fishing rod. of the radiator and
attach them at the same point where u attached the radiator.
final small adjustments that a nice square is produced.
lasting results you could improve the coax connection, get rid of the
T-reps. and a paint on those fishing rods would not be misplaced.
I made for this project was in the order of 40 euro's I believe this
could have been around 25...30 euro's simply because I bought fishing
rods that were 4 meters long but 3 meters can do the trick as well.
For the first time building you will probably need about 3..4 hrs to
make everything right, that's not bad for an antenna that will work
as good as any 3 elements yagi!
please send an e-mail!