More on Antenna Modelling

Nathan Cohen in the US has ‘fractalised’ the quad loop, based on the Minkowski Square, and he has invented an array of two elements. It is thought that the biggest advantage of fractal antennas is that you achieve a wide bandwidth with a small size.

This (AN-SOF) simulation (see URL below) shows that we can almost double the bandwidth with a 3-element array. It has a reflector, a driven element, and a director.

These are the results for the 20 m band (14MHz),

• Quad size: 290 x 290 cm (0.14 x 0.14 of a wavelength)
• Element spacing: 280 cm
• 450 Khz bandwidth (VSWR < 2) around 14.5MHz
• 6 dBi gain
• 10 dB F/B
• 80° beamwidth
• Vertical polarization.

It has less gain than could be achieved with a 3-element Yagi, but it has a relatively large bandwidth and is a very compact antenna. It does not need a matching circuit and its impedance is 50 Ω at resonance, so it could be fed directly through a 50 Ω coax.

You can download the model here:

https://antennasimulator.com/.../AN-SOF_Fractal

(Source: Keith Rawlings)

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