Reception of phase-locked l.f. and m.f. transmissions by receivers having ferrite-rod antennas

If two l.f. or m.f. transmitters share a common frequency, there is a region between them where the signals are both equal and in antiphase. Receivers with ferrite-rod antennas experience poor reception in this region only on or near the axis joining the transmitters. Elsewhere, the magnetic fields act in different directions and do not cancel; continuous good reception can then be achieved by phase-locking the transmitters.