Α radio communication service that has as aim the self- teaching,  the communication with each other,  the technological research, and the  telecommunications support of  enterprises of help in cases of situations of an emergency and of destructions that are carried out by amateur, that is to say by persons  permitted to deal with the radioelectric technique exclusively for personal aim and without economic profit.



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YAGI 3 ELEMENTS 7db Gamma Match Portable



FREQUENCY : 144 -146 MHZ - GAIN: 7DB  Front to back ratio 35 db. - VSWR :< 1.1 - MAX POWER RATING : 500 WATTS


Construction of antenna Yagi 3 Elements with Gamma Match, Portable.

The construction of the antenna is quite easy. I used the materials i had in storage from older constructions.
The antenna used in two peaks at low altitude and gave excellent results for its length.

 You will need one meter of square aluminum tube BOOM 20X20 mm and tube Φ 12 mm. about 4 meters. Rods aluminum Φ 6 mm, Teflon (Polytetrafluoroethylene or PTFE) or ERTALON which is easy to found and  cheaper. Plastic cover 20x20 mm, 1 female connector N TYPE for chassis preferably screwed.
The antenna coordinates in the 2 meter band 144 - 146 MHz Without a critical coordination.
Let's see  the dimensions of the antenna.

Reflector :
148 / f  In the particular case f is 145,500 MHz frequency
148/145.500 = 101718
 Final length of  reflector is 1017 mm

Dipole    or active element:
L = 300 / f = 300/145, 500 = 2,0618 is the wave's length which will be used  again later.
L / 2 = 1, 030 we will multiply by 0.925 and  will get  the final length of the active element, which is 954 mm

134 / f = 134/145.500 = 0,9209. The final length of the director is 920 mm.
These are the final lengths of the antenna.

To sum up, so far we have:

REFLECTOR                               =  1017 mm
Dipole or DRIVEN ELEMENT  =    954 mm
DIRECTOR                                   =    920 mm

Now we are going to find the distances between them.
Reflector - Dipole
0.2 x L = 0,2 x 2,0618 = 0.41
Dipole - Reflector
0.1x k = 0.1 x 2,0618 = 0,20618
20,6 cm.
Or even better with a slight increase in length
0.175 x L = 0.175 x 2.0618 = 0.360815

 36 cm.

The distance of the dipole collimator can get prices up to 0.2L

The distances are among the elements in other words at the point that ends the element of the Reflector we measure 41 cm and install  the active component of the Dipole and at the point that finish the element of dipole we measure 20.6 cm and install collimator.

Gamma matching

we are going to use a stable capacitor 12 pf for gamma match. In this way we save weight since the antenna is mending for portable use. We connect one of the ends of the capacitor in the central pole of the connector and the other in small screw of gamma match.  Do not  try  to stick to aluminum, the soldering is not going to be affective. We pierce a point of the gamma match and we a little screw at the top as you see in the picture.

In total the length of gamma match is 350 mm.

There's still the jumper which is a rectangular piece of aluminum with dimensions 11 x 56 x 18, H x W x B with two little screws sideways to keep the elements tight. The distance between the active element and gamma match is 2 cm.
The construction is easy. Firstly we count and check the distances to the boom and then drill vertically, on a base so as the elements remain vertically without leaning right or left.
After we drill the elements in the middle in order to install the screws. Our next move is to construct the box the connector.

We Pierce at first for the connector, the side of the  3x3  box ,and  3cm at the bottom we adjust the Teflon in order to fit perfectly. After the hole in the Teflon for the tube of  the gamma match and we are ready. Take a look at the Photos. They gonna help you a lot.


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YAGI 3 ELEMENTS 7db Gamma Match








All the antennas that I construct, I want them to be strong and long-lasting.

Of course i want it to be light weighted, when it's portable. The construction is simple. Searching on Google I found this plan. In explicit detail, I would say it's easy, without any hard-to-find materials. Thought I've made a few modifications. When I started the construction, I used materials that I had already stored .But now let's move on the construction of the antenna.


1 Copper tube cu Φ15

1 Equal Tee cu cu Φ 15

1 90░Elbow cu Φ15

1 piece of Teflon 95X30 mm (drawing C)

1 Racor for Φ15 for portable use only

1 SO 239 connector

 For the construction of the antenna, it's necessary some experience, regarding the soldering, but there aren't any technical difficulties.

We will also need some tools like:

A measure

A hacksaw or a pipe cutter

Propane device, soldering, soldering paste

(You will find them in stores that sell plumbing equipment)


 Calculate the dimensions of the pieces. Start out by cutting them according to the dimensions, that you want the project to have. Always remember that for any type of construction, it's wise to measure twice and cut once! After cutting them, use the sandpaper in the places that are going to be soldered. This kind of work should be done in a workbench, so as the pieces are aligned. If you follow the dimensions of the project, you will have a static 1:1 SWR.

Begin by soldering the pieces as it's shown in the pictures. Apply the soldering paste in the place to be soldered and heat the tube with circular motions with the blowtorch (mapp gas). When the tube is heated and the soldering paste has melted and foamed, we use the soldering. That's all. Be careful not to burn yourself!

With the use of devices such as mapp gas it's needed that we take all precautionary measures and follow the instructions.

We solder all the pieces and now we solder the connector, heating it as little as possible in order not to destroy the insulator Teflon or Bakelite It's better if we have tied a little wire at one side of the connector, in order to solder properly. After the process, we cut it. Join the connector's positive edge with the single wire 2.5 and go to the opposite tube. Then spin it and solder it as well.

About the version J POLE PORTABLE, it's needed to be cut to the point that the design is showing and then solder the Racor. I prefer the Racor because it screws and unscrews many times without a problem. In order to make the J POLE PORTABLE more strong, put the Teflon piece as it is shown in the drawing C before you solder the Racor. In the end, the antenna was cleaned. I used the sandpaper in all of it's length and a special paint for non-ferrous metals.

 I've taken this antenna in several mountains. The reason is that it is easy to assemble and has a good reception. Of course, if it is compared to the Yagi Gamma Match 3 Elements that I have made, it is quite below, according to the reports, that I've taken. It's advantage is its circular polarization. From SHACK and especially from Tripolis it opens several transponders like RO Laconia, RI Athens, R2 Dolianon and R7 Penteli. So, it competes the commercial antennas.

The tests are about to continue so as to make some final conclusions. For this construction I would like to thank my friend Kostas c190 for his valuable help. Take a look at the Photos.

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The designs of the antenna are from DK7ZB's site.

The antenna gain is 8.2 db.

It consists of
1 reflector
1 radiator
3 directors
The antenna dimensions are the following:
new design (Nov.2008) for better pattern:



Lengths 2,4mm






995mm (4mm)

Director 1



Director 2



Director 3



The boom is from electrical tube PVC KOUVIDIS CONDUR Φ 25 HEAVY TYPE 1250N length 1500 mm.
The data are from 2.5 mm brazing except of the dipole that is 4 mm.
The structure was designed in order to have less weight and better durability.
Also great attention was given to the assembly time of the antenna which is as short as possible.
Designed for portable use and not for permanent installation!
The construction of the antenna has several difficulties such as: Tapping screws in the center to pass the item. The incorporation of the boom required a lathe for the ERTALON pieces. The base of the connector is from properly processed aluminum. The antenna consists of two parts to be easily transported. The dipole screws onto the screws threaded and they're screwed into an ERTALON piece located snugly in the tube of the boom. It coordinates wonderfully throughout the band.

For further details look at the pictures.

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Last Update: 04 / 01 / 2018.