2.5GHz Loop Yagi Antenna
Loop yagis are basically a hybrid design of a tuned loop in a yagi type array.
The best material to use for the construction of a loop yagi is brass, or copper.
Brass is the better choice since it is easier to solder and corrodes less than
copper. You may solder, bolt or even brase your antenna parts together.
I use brass for my antenna and copper waterpipe for the boom.
The brass elements I bought from my local hobby shop and cut them to length and bent
them into shape. For 2400MHz the driven element should be 130mm long and for the
directors they should be 120mm long. All elements should be 10mm wide.
Each of the dirrectors is bent into a circle and then ends soldered together.
What you should have is something that looks like a brass egg ring. Each element
is then soldered or bolted to the boom at the correct spacing according to the table.
The Driven element is slightly different. The driven loop is not soldered closed,
the core of the coax is soldered to one side and the other to the shield.
The only type of coax that you should consider using for this antenna is semi-rigid
coax. To mount it correctly you should have a hole in the boom big enough for the coax
just to fit through and a holde in the bootom off the loop. Feed the coax through the
boom and through the loop and solder the coax to the open ends. Then solder the shield
to the bottom of the loop and finally solder the loop and the coax to the boom.
Finally attach a fine wire mesh or sheet of metal to the rear of the boom to act as a
reflector and your done.
This is a nine element brass loopy yagi without its reflector installed.
This antenna to about an hour to make from scratch.
An example of a loopyagi in use. The antenna is on it's side so that the polarisation is vertical.
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