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Some people have replaced the fixed antenna on their PMR equipment with a coaxial connector which allows them to use external antennas

I will in the following describe a four element Yagi antenna I designed and built for the PMR band, it is a real low cost design and easy to put together.

The goal was to make a design that require not to much experience and use of ordinary tools possible to find in almost every household, as an example, there is no need for a drilling machine.

List of materials (All measurement in mm)

Number	Type	Dimension	Length	Remarks
1	Wood Strip	21 x 15	600	Boom
4	Wood Strip	21 x 8	100	Support
8	Nails
1	Aluminum Tube	Ø12	326	Reflector
2	Brass Tube	Ø12	150	Driver
1	Aluminum Tube	Ø12	271	Director 1
1	Aluminum Tube	Ø12	261	Director 2
16	Plastic Strip		Min 120

od frame

The antenna consist of a wood frame, see figure 1. The dimension used is not critical, I used two different dimension of wood strip, boom

dimension is 21 x 15 and the four supports is 21 x 8. The frame is glued and nailed together. The supports shall be mounted in right angle to the

When you are ready with the frame it has to be painted. It is necessary, because it have not to take up any moister which can affect the

performance of the antenna. You can use a metallic boom instead, but in this design is it necessary to isolate all the antenna elements from the

The antenna element I used is aluminum and brass tubes with the diameter of 12mm. The brass tube is used for the driver

because it is possible to solder the coax cable to it.

All antenna elements can without problem be changed to brass or copper tubes with the diameter of 12mm, use tubes with

a thin wall to keep the weight down.

The reason using such fat elements as 12mm is because it gives the antenna wider bandwidth which makes the design less

sensitive for variations in the built up.

It is not possible to change the diameter of the antenna elements to a smaller size without recalculating the design, because

the performance of the antenna will change.

Assembly antenna element

To attach the antenna elements to the Wood frame I used plastic straps, it is easy and fast, see figure 3, 4, 5.

When you assembly the driver element leave a gap of 2mm between the two element halves, see figure 4.

Soldering the coax cable

In this text I will not describe how to split up a coax cable, you can find it some where else at the web.
IMPORTANT, do not forget to seal the coax cable after you have split it up, to avoid it to take up moister.

Also the solder joints must be sealed, use epoxy, glue, paint or what else you have in house.

When you solder the coax cable to the two halves of the driver, heat up the tubes first, it takes some seconds for the brass tube to heat up.

Apply a small amount of solder and let it melt before you solder the coax to the tubes. In figure 6 you can see the coax cable connected to

Antenna performance

In figure 7 you can se the complete antenna. The performance of this antenna is rather good, wide bandwidth with a good match to

List of materials (All measurement in mm)