ANTENTOP- 01- 2008, # 010

Two Elements YAGI for 145 MHz:

Balcony Project

Compare to 2-5/8 and 3-5/8 collinear the Two Elements YAGI has more gain. Experience shows that the more distance between radio stations the more Two Elements YAGI beat the collinear. My Two Elements YAGI has room near 100-centimeters x 40 centimeters. Collinear antenna that has close to the Two Elements YAGI gain is 3-5/8 collinear. Such collinear has height near 5 meters. So, what is easy to install at the balcony?

Two Elements YAGI loses 1-dB in gain compare to Three Elements YAGI. However, Two Elements YAGI has boom twice less in length compare to Three Elements YAGI. That is why I have chosen the Two Elements YAGI.

And the last. Why I did configuration "Vibrator- Reflector?" Because the combination has good forward gain thought not good suppression of back lobe. Combination "Vibrator- Director" has good suppression of back lobe but bad forward gain. I need good forward gain.

Figure 1 Design of the Two Elements YAGI.

Design.

Figure 1 shows the design of the Two Elements YAGI. Antenna elements are made from aluminum tube in 10-mm diameter. Traverse made of from L- Shape aluminum with sizes 20x20 millimeters. Antenna has input impedance 50-Ohms, so, coaxial cable straight away turns on to the antenna.

Several ferrite rings (that do an RF-Choke) are installed on the coaxial cable near feeding terminal.

Vibrator is insulated from the traverse. Plastic pieces are installed between antenna elements and traverse. The pieces made from a water pipe with OD 20-millimeters (3/4 inches). Length of 70 millimeters is cut (longitudinal section) on to halves. One piece is going for vibrator another one to reflector. At the vibrator's piece drill a hole in the centre.

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