4. Operating System and Equipment
Reception Form of AM/FM Vehicle Audio
VHF channels on FM will pass through the
ionosphere directly without reflection, but once they
hit high mountains, high-rise buildings and other
barriers, they will produce reflection. FM spreading
distance is usually about 40~50 kilometers. It will
become shorter when stereo signals are
transmitted.
The radio is far away from the broadcasting
station, so the signals are too weak to be received.
As a result, the radio will only receive noises. When
the vehicle is driven between the areas to receive
two strong stations with a close signal frequency at
the same time, the radio may lose sound suddenly
or produce noise interference.
Although MW or SW of AM cannot pass
through ionosphere, it will produce diffraction. As a
result, when the radio waves hit high mountains
and high-rise buildings, its spreading distance will
be farther than that of FM. Therefore, it is likely to
simultaneously receive the signals from two AM
stations.
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