Marconi's
system, however improved it may be to-day, has one grave defect. The
synchronism of the two pieces of apparatus, the transmitter and the
receiver, is not perfect, so that a message sent off by one station
may be captured by some other station. The fact that the phenomena of
resonance are not utilised, further prevents the quantity of energy
received by the receiver from being considerable, and hence the
effects reaped are very weak, so that the system remains somewhat
fitful and the communications are often disturbed by atmospheric
phenomena. Causes which render the air a momentary conductor, such as
electrical discharges, ionisation, etc., moreover naturally prevent
the waves from passing, the ether thus losing its elasticity.
Professor Ferdinand Braun of Strasburg has conceived the idea of
employing a mixed system, in which the earth and the water, which, as
we have seen, have often been utilised to conduct a current for
transmitting a signal, will serve as a sort of guide to the waves
themselves. The now well-known theory of the propagation of waves
guided by a conductor enables it to be foreseen that, according to
their periods, these waves will penetrate more or less deeply into the
natural medium, from which fact has been devised a method of
separating them according to their frequency.
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