ANTENTOP- 01- 2015 # 019

Dipole Antenna for 40- and 20- meter Bands

Antenna dimensions are depended on the placement and inductance of the inductor. However the inductance of the inductor is not critical for antenna operation. Most important thing is that the inductors have the same inductance. In my case the inductors (measured by me) have inductance 31.4- micro Henry. The inductance is influenced to the parameters of the antenna. The more it is inductance of the inductor the less length of the parts of the antenna and the less passband of the antenna.

Antenna was placed at the mast in 7- meters height. The mast was made from a fiberglass plastic. Antenna was made from stranded wire in plastic insulation. Antenna was fed through 50- Ohm coaxial cable. the antenna.

I have used RG 313 type. This cable was going along the mast and then going underground to my shack. Length of the cable was near 20- meter. Weather practically did not influence to the antenna.

Antenna was easy tuned to SWR 1:1 at both Bands. Antenna had bandpass near 200- kHz (at SWR 1.5:1) at the 20 meter Band and bandpass near 75- kHz (at SWR 1.5:1) at the 40 meter Band. At first step the antenna should be tuned at the 20- meter Band by symmetrical changing lengths of the parts A. Then antenna should be tuned at the 40- meter Band by symmetrical changing parts B. Changing the length of the parts B practically did not influenced to the operation at the 20- meter Band.

Figure 2 SWR of the Dipole Antenna for 40- and 20- meter Bands from 5 to 19.5- MHz

Figure 3 SWR of the Dipole Antenna for 40- and 20- meter Bands at the 40- meter Band

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