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Frequently Asked
Questions
FCC Part 90 Rules
Signal Penetration
Skywave
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Information radio
stations may be licensed
to governmental entities
or to emergency
medical/healthcare
providers sanctioned by
such entities. The legal
name for the stations is
Travelers' Information
Stations, and the
governing rule section
within FCC Rules is
Part 90.242 (linked at
the bottom of this page). |
Content Limitations |
See our
Permitted Broadcast
Content webpage, which
provides a formula for
analyzing intended
broadcasts to
ensure they fit within
FCC guidelines. |
Technical Limitations |
The audio bandwidth of
information radio
stations is limited to 5
kHz by new
FCC rules,
which is the same
bandwidth many standard
broadcast stations use.
Before 2015, information
stations were limited to
3 kHz of bandwidth. This
is to prevent the
stations from
interfering with
standard broadcast
stations.
The height of
information radio station antennas is
limited to 49 feet above
ground level.
Exposure risks from such
stations are minimal,
due to the relatively
low RF power levels
involved. Even so, it is
prudent to maintain a
one-meter separation
from the antenna and its
support structure, when
it is in operation to be
in compliance with FCC
guidelines. |
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
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.
Receiving their signals inside
of
structures
depends 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. |
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 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
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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