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4. For MW, due to the characteristics of radio waves, more radio stations can be
received during nighttime than daytime.
5. It is advised to repeat the ATS function for SW from time to time, since SW
reception is affected by a variety of factors. SW radio waves are affected by the
condition of the ionosphere, which varies according to the time of day, seasons
and the state of the sun. SW transmissions are also not continuous, which means
that these cannot be received the whole day. Furthermore, the receiving
environment or the receiving equipment such as the (external) antenna used, will
also affect the ATS result.
Broadcasting knowledge:
Why are more MW stations received at night than during the day?
MW stations emit radio signals or "waves" in two ways: (1) along the surface of the
earth, so-called "ground waves", and (2) by letting the signal travel from the radio
transmitter and then bounce off the ionosphere in the atmosphere back to the
surface, the so-called "sky waves". Ground wave propagation is generally not more
than two to three hundred kilometres, due to a strong absorption effect by the
surface of the earth.
During daytime, the ionosphere density increases under the effect of sunlight, making
sky wave ionospheric propagation difficult. Signals are partially absorbed by the
ionosphere with only limited reflection back to earth. Because ground waves are also
easily absorbed by the earth, this results in MW signals not being able to spread over
long distances. Therefore, during daytime, it is quite difficult to receive long-distance
MW broadcasts.
During nighttime, the ionosphere becomes thinner because the atmosphere is no
longer exposed to sunlight. A significant reduction in electrons and ions in the
ionosphere reduces its absorption effect of MW radio waves. MW sky waves are
more easily reflected back to earth and can spread over longer distances, which is
why more MW stations can be received at night.
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