ANTENTOP- 03- 2003, # 004

Igor, UA6HJQ, ua6hjq@mail.ru

I need a good universal antenna for repeaters working at the 70-cm range, packet radio and for routine work. Such antenna must be satisfy the follow characteristics:

1. Real Gain 9-10-dB.

2. Low SWR at 430-440- MHz.

3. Wide forward lobel.

4. Unpretentiousness to close located subjects.

5. Simplicity in manufacturing and adjustments.

6. Possibility to create phased systems on the basis of the antennas.

7. 50- Ohm coaxial cable feeding.

8. Stability to heavy icing and to winds in 10-20 meters per second..

4 Ovals Antenna responded all of the conditions. Why an oval? At first, from the antenna theory we know that an oval radiates energy a little bit more effectively than a square. At the second, in practical, it is more easy to do an oval then a square.. So choose the OVAL! Figure 1 shows a design of the

antenna. Boom is made of iron L-plate 25x25-mm. All the four ovals are fastened to the boom by struts made of insulation stuff such as tree, hetinax, etc. Antenna is fastened by the tail, that is behind the struts.

Perimeter of elements (ovals):

Reflector- 727-mm. (-20-mm for soldering).

Driven Element: 653-mm (+10-mm distance for a RF socket).

Director-I: 649-mm. (-20 mm).

Director- II: 639-mm. (-20-mm).

Figure 2 shows the design of the Driven Element. RF socket is soldered directly by the ends of the oval. Three holes is drilled at each strut. One holes is in the center for fastened the strut to the boom, two holes are at the ends for bimetal oval. Antenna reflectors and directors have the same design as the Driven Element only difference is its ends soldered together.

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