5 to 28 MHz Random wire antenna – 12.8m (42 ft)

Some time ago I had a S2S-QSO with N1ZF. In the following e-mail contact we exchanged information and photos about the antennas used for this QSO.
This is when I became aware of the „Random Wire Antenna“ that Paul had successfully used. It consists of a 12.8 metre long wire as radiating element and an equally long ground radial. Matching is done with the KX3’s internal ATU. Since the ATU cannot match any impedance, it is important to choose a wire length that is not a multiple of half a wavelength. This way the „odd“ length of 12.8 meters emerges.

The antenna is available from SOTAbeams under the name ‚Bandspringer Midi‘. The design is very simple, which makes it a candidate for homebrewing. Only pre-requisite is a transceiver with internal ATU.

2020-11-17 14.11.34
Both wires are connected directly to the KX3 through a suitable BNC adapter. I prefer forked cable lugs over 4 mm ‚Banana‘-plugs.

The radial is laid on the ground, the radiator is stretched in any configuration possible (vertical, inverted L or inverted Vee). The internal ATU of the KX3 is able to match all bands from 60 metres to 10 metres with a VSWR << 2:1 (somtimes it will need a second attempt for this).

The main advantage of this antenna compared to my other end-fed half-wavelength antennas is its lower weight. This is because the wire is shorter and no separate ATU or UnUn is needed. Additionally, band changes can be done even faster than with the QRP-L-Tuner.
So far I have done about 100 QSOs with this very simple antenna (thereoff 20 with NA) and I am impressed by its performance.

Further information about random wire antennas can be found here:
http://www.arrl.org/random-wires
https://udel.edu/~mm/ham/randomWire/

2020-11-17 14.11.39 (Kopie)

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