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Electronic Sound Systems
If there is a building or large structure between the antenna and
station, some of the signal "bends" around the building, but
certain spots receive almost no signal. Moving out of the
"shadow" of the structure will allow the station to return to
normal.
This condition exists when the radio waves are reflected off
objects or structures; the reflected signal cancels the normal
signal, causing the antenna to pick up noise and distortion.
Cancellation effects are most prominent in metropolitan areas,
but also can becomes quite severe in hilly terrain and depressed
roadways.
To minimize the effects of these conditions, a stereo/mono
blend circuit has been incorporated into this system. This feature
automatically switches a weak stereo signal to a clearer
monaural signal, which improves the quality of reception.
Several sources of static are normal conditions on AM
frequencies. These can be caused by power lines, electric fences,
traffic lights and thunderstorms.
Another reception phenomenon is Strong Signal Capture and
Overload. This can occur when listening to a weak station and
when passing another broadcast tower. The close station may
capture the more distant station, although the displayed
frequency does not change. While passing the tower, the station
may switch back and forth a few times before returning to the
original station.
When several broadcast towers are present (common in
metropolitan areas) several stations may overload the receiver,
resulting in considerable station changing, mixing and
distortion.
Automatic gain control circuitry for both AM and FM bands has
been incorporated into this system to reduce strong signal
capture and overload.
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