Interior Features; Weak signal noise- Page 492

has even less range than monaural
(non-stereo) FM.

FM Station

40—50km 
(25—30 miles)

Signals from an FM transmitter are similar
to beams of light because they do not bend
around corners, but they do reflect. Unlike
AM signals, FM signals cannot travel
beyond the horizon. Therefore, FM
stations cannot be received at the great
distances possible with AM reception.

AM wave

FM wave

FM wave

100—200 km (60—120 miles)

Ionosphere

Atmospheric conditions can also affect
FM reception. High humidity will cause
poor reception. However, cloudy days may
provide better reception than clear days.

Multipath noise

Since FM signals can be reflected by
obstructions, it is possible to receive both
the direct signal and the reflected signal at
the same time. This causes a slight delay
in reception and may be heard as a broken
sound or a distortion. This problem may

also be encountered when in close
proximity to the transmitter.

Reflected wave

Direct

Flutter/Skip noise

Signals from an FM transmitter move in
straight lines and become weak in valleys
between tall buildings, mountains, and
other obstacles. When a vehicle passes
through such an area, the reception
conditions may change suddenly, resulting
in annoying noise.

Weak signal noise

In suburban areas, broadcast signals
become weak because of distance from the
transmitter. Reception in such fringe areas
is characterized by sound breakup.

Interior Features

Appendix

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2020-1-8 11:19:15