ANTENTOP- 01- 2010, # 012

Simple Field One- Wire- Length HF Antennas

Expedition antenna for the bands should have length not less the 9 meter and no more the 21 meter. Why? Because we need antenna that would be work without counterpoises, so, the antenna should have length lambda or lambda/2. Shorten antenna has low efficiency, long- high weight.

Wire in length 10-meters would be enough if you would like to use bands 14- 28- MHz at the expedition. Antenna with such length is suitable for local and DX- QSO on 14- MHz and has good efficiency on 18- 28- MHz. Such antenna still is working on 7-MHz (lambda/4 length).

Wire in length 20-meters would work efficiency on 7- and 14- MHz as well as at 18- 28- MHz. The antenna provides local QSO at the 3.6- MHz. However at good propagation and if the end of the antenna is hanged up at 10 and more meters the antenna allows to make DX-QSO on the 3.6- MHz.

...How would it hang up?

Classical mountain expedition antenna is Sloper. Figure 1 shows the antenna. Use any natural support- tree, stone, etc., to install the antenna.

Figure 1 Expedition Antenna Sloper 10- meters length

For Sloper having length 20 meters use additional support. It may be any natural support- tree for example, or artificial- plastic fishing pole, for example. Figure 2 shows Sloper 20 meters length. DD of the antennas shown on Figure 1 and Figure 2 has maxima radiation in direction of the incline of the antenna wire.

Antenna wire may be placed along the fishing pole. DD of the antenna has maxima radiation into another side from the incline of the wire. Figure 3 shows Sloper with fishing pole as antenna part.

It is possible to install support or fishing pole at any place of the wire. In this case it is a variant of an asymmetrical dipole with the end fed. Figure 4 shows the antenna. Good solution is to install the support in the center of the antenna wire how it is shown on Figure 5. In this case we have got a kind of I.V. antenna with the end fed. The antenna has enough efficiency at 7- and 14- MHz.

The feature of the Sloper antennas on the base of one wire is that all of the antennas are radiated almost 50/50% horizon/vertical polarization. It looks like a lack of the antennas. If you need antenna with the vertical polarization you may try helical antenna shown in the Figure 6. However the antenna needs good grounding or counterpoises.

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