Newnes Radio and RF Engineering Pocket Book, 3rd Edition

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Figure 4.17 Axial mode helical antenna

4.5 Loop antennas

4.5.1 Small loop antennas defined

Large loop antennas are those with overall wire lengths of 0.5λ to more

than 2λ. Small loop antennas, on the other hand, have an overall wire

length that is much less than one wavelength (1λ). According to a

Second World War US Navy training manual such antennas are those

with an overall length of ≤0.22λ. Jasik’s classic 1961 text on radio

antennas uses the figure ≤0.17λ, while John Kraus (1950) used the

figure ≤0.10λ. An amateur radio source, The ARRL Antenna Book,

recommends ≤0.085λ for small loop antennas. For the purposes of

our discussion we will use Kraus’s ...