SX BLUE GPS iSXblue II+ GNSSTM, Руководство пользователя

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SXblue Series User Manual 51
2.3.1 RadioBeacon Range
The broadcasting range of a 300 kHz beacon is dependent upon a number of
factors, including transmission power, free space loss, ionospheric state, surface
conductivity, ambient noise, and atmospheric losses.
The strength of a signal decreases with distance from the transmitting station, due
in large part to spreading loss. This loss is a result of the signal’s power being
distributed over an increasing surface area as the signal radiates away from the
transmitting antenna.
The expected range of a broadcast also depends upon the conductivity of the
surface over which it travels. A signal will propagate further over a surface area
with high conductivity than a surface with low conductivity. Lower conductivity
surfaces, such as dry, infertile soil, absorb the power of the transmission more than
higher conductivity surfaces, such as sea water or arable land.
A radio beacon transmission has three components:
•
Direct line of sight wave
•
Ground wave
•
Sky wave
The line of sight wave is not significant beyond visual range of the transmitting
tower and does not have a substantial impact upon signal reception.
2.3.2 Signal Reception
Various sources of noise affect beacon reception and include:
•
Engine noise
•
Alternator noise
•
Noise from power lines
•
DC to AC inverting equipment
•
Electric devices such as CRT’s, electric motors and solenoids
Noise generated by this type of equipment can mask the beacon signal, reducing
or impairing reception.
When using the internal beacon receiver as the correction source, selecting an
appropriate location for installation of the antenna will influence the performance
of the internal beacon receiver. The following list provides some general guidelines
for deciding upon an antenna location: