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.
- 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.
- 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