The coverage statistics and maps
are calculated using a computer model and station data assuming
ideal conditions. Coverage may be 5 to 10 percent below
the computer predicted coverage for the following reasons:
The computer model is sensitive to antenna performance.
Antenna performance is a function of local conditions,
causing signals to be stronger signal level in some
directions than others.
Most NWR stations are at existing antenna towers,
provided at little or no cost.
Placement of NWR antennas is dictated by the tower
owner, which may result in a less than ideal set up.
The antenna may be affected by nearby structures or
bodies of water.
In some special instances, the antenna may have been
intentionally adjusted to be "directional"
and provide better coverage to a specific area to the
detriment of other areas.
Most of the stations employ equipment technology more
than 20 years old. Because of variations in local site
conditions, the performance of an individual transmitter
and antenna may be less than predicted or expected.
Seasonal environmental conditions, such as icing or
heavy rain, affect performance of a transmitter station
and its various components, particularly those subject
to continuous weather exposure.
The coverage maps are shown in a single color format,
which relates to an estimated signal level.
White: Signal level of greater than 18dBuV: Reliable