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Licensee Limitations
Information Radio Stations may be licensed to
governmental entities or to emergency medical/health care
providers sanctioned by such entities. The legal name for the
stations is Travelers Information Stations, and the governing
rule section within the FCC Rules is Part 90.242. |
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technical Limitations
The bandwidth of Information Radio Stations is
limited to 6 kHz by FCC rules to prevent them from interfering
with standard broadcast stations, which have a 10-kHz bandwidth.
This bandwidth limitation can make broadcast messages sound “bassy,”
if messages are not equalized.
The height of Information Radio Station antennas is limited to
49 feet above ground level. |
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Signal Level Limitations
Information Radio Stations have 0-10 watt power
levels that are significantly lower than standard broadcast
stations, which is why their coverage areas are much smaller.
Because of this, their peripheral signals can be more vulnerable
to interference from a variety of terrestrial sources, nighttime
skywave interference and blockage by structures and terrain
features.
…Power lines and bridges – can distort (add hum) or
temporarily block signals, when the receivers are in the
immediate proximity.
…Nighttime “skywave” interference – can create the
perception of lower range by adding competing on-channel noise
during the dark hours. This can be especially pronounced on AM
frequencies that are shared with many standard broadcast
stations.
…Terrain features such as mountains, steep cliffs and
valleys, etc., can block signals when the listener is in
the immediate proximity.
…Noise from active interference sources such as
automobile engines, electrical systems and onboard computers can
limit the range at which a particular vehicle can clearly
receive radio signals. Likewise, passive sources such as the
presence of a poor receiver or poor receiving antenna on the
vehicle can produce the same effect.
…Information Radio Stations are designed specifically for
in-vehicle listening. Attempting to receive Information
Radio Station signals in structures will differ depending upon
many variables, including the distance of the building from the
Information Radio Station antenna, the composition of the
building walls, interference sources (computer systems) that
might be present in the building, and the type and placement of
the receiver and receiving antenna with respect to the building. |
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Service coordination Limitations
Information Radio Stations are a secondary service.
Standard broadcast stations are primary, which means that
Information Stations must make way for any changes that standard
broadcast stations would make in their service. Such changes
could include the introduction of a new broadcast station or an
increase in the power or bandwidth of an existing AM broadcast
station. Information Stations must accommodate these changes,
even if it would mean changing channels or ceasing to operate.
Fortunately this rarely, if ever, happens due to the fact that
the AM spectrum is nearly gridlocked on most channels and there
is little room for change. In fact, to date, there has never
been an instance of an Information Station being required to
cease operation due to a change in service by a broadcast
station, though there have been a few isolated instances in
which an Information Station was required to change channels in
order to continue operation.
Information Radio Stations licensed at fixed geographical points
are protected by a 9.3 mile buffer. FCC rules prevent other
fixed-point Information Stations from licensing on a given
frequency within that distance.
Portable Information Stations that are licensed to roam on a
temporary basis within a territory (because they are moveable)
are not similarly protected from encroachment by fixed-point
Information Stations. Additionally, portable stations must not
operate within 9.3 miles of fixed point stations on the same
frequency that are licensed within or near their operating
territory, including those that might be licensed subsequent to
the granting of their license to operate within the territory. |
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This page
was last updated on
November 11, 2010. |
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