Absorption of radio transmissions near the geomagnetic equator at medium frequencies

Electromagnetic waves entering the ionosphere are split by the Earth´s magnetic field into two “characteristic waves”, the ordinary wave (O-wave), and the extra-ordinary wave (X-wave) which suffers heavy absorption at medium frequencies (MF). This paper provides the basis for software to predict the polarisation match for a transmit antenna, and reviews initial measurements made near the geomagnetic dip equator.