I love a good Yagi. I also love folded dipoles. So why not mix the two up and make a nice Yagi driven with a folded dipole?
This 12 element monster is easy to make and produces a theoretical 12.75 dBd gain. The dimensions were calculated using this tool. The details are:
434.000 MHz, 12 Elements, 12.75 dBd Estimated Gain
34.0 Degrees Horizontal Beam Width
35.6 Degrees Vertical Beam Width
4.000 mm Driven Element Diameter.
4.000 mm Parasitic Element Diameter.
2.0 mm Dimensional tolerance required for element lengths.
I won’t go into element spacing as the tool will tell you everything you need to know. The spacing will also change depending on the size of your elements.
You will need
A folded dipole for your chosen frequency. Don’t have one? Build a jig by following these directions.
2000mm x 30mm x 15mm length of wood.
Some lengths of 4mm steel rod (or whatever you are using for elements).
Super glue
Step 1
Take your boom and mark out the correct positions for the elements.
Step 2
I used a router with a 4mm drill bit to create the holes for my elements. It is important to get the holes completely straight otherwise you will end up with wonky elements!
Step 3
Cut the elements to length and insert in the correct order. Do not do the reflector yet! Add a small blob of glue to secure in place.
Step 4
Assemble the folded dipole and place in position. I secured it to the boom with 2 small screws.
Step 5
Insert the reflector element and secure.
Results
The Yagi is performing very well. From the garden, it picks up repeaters that I can’t hear on a roof mounted collinear and it appears to be very directional. It’s going up on the roof soon so we shall see how it does.
