ANTENTOP- 01- 2011 # 015

Efficient Field Low Height Dipole Antenna

for the 20- meter Band

Igor Lavrushov, UA6HJQ

Credit Line: http://www.hamradio.cmw.ru/antenna/upa14.htm

The antenna was designed for using in a mountain hiking where the main requirement is a low weight and high efficiency at the limited stuff around there.

Field test shows that the antenna has almost circle diagram directivity.

Antenna Design

Why symmetrical dipole antenna?

Symmetrical dipole antenna is mostly fitted for the field conditions. Military, geologist expedition, rescue and emergency communication service- all of these are used a dipole antenna. The antenna works well in the near zone (100- 200- 300- km, depends on the Band) that is needed for communication from a mounting trip. It is important that the antenna would have some gain because in the mountain it is used a QRP-equipment. Dipole antenna works well in the forest, in the deep ravine, among tents in Alpinist Camp. Figure 1 shows design of the dipole antenna. The antenna has gain plus 5- dBi.

The antenna is a symmetrical dipole (with length a little bit more the lambdaé4) installed on the top of a plastic fishing pole. The antenna is fed by a 50- Ohm coaxial cable. The cable is matching with the antenna with the help of two fixed capacitors. One is connected to the central core another one is connected to the braid of the coaxial cable. The value of the capacitors (50- 200- pF) should be found out for the current antenna system. Coaxial cable at the feeding terminal is coiled (2- 3 turns) on to a ferrite ring. Capacitors and the ferrite ring should be protected from moisture. Those ones may be placed into a plastic box (from an old 35- mm film) or shrinked.

Figure 1 Field Dipole Antenna

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