Datawell 45100, Руководство пользователя

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Appendix A: Buoy HF data link and range
The Waverider- and Directional Waverider Buoys send their data to the shore using a HF data
link. This data link system can be represented by the functional block diagram shown in
figure
A.1 , and consists of a buoy with its transmitter and transmit antenna, a channel –the atmosphere
through which the buoy signals are wirelessly transmitted- and a receiver, namely the RX-D2
and its receiving antenna. Those functional blocks will be described in the next paragraphs,
together with technical details, error sources and solutions. An estimation of the HF range of a
buoy-receiver system can be made with the numbers in decibels or decibel milliwatts and the
calculation at the end of this appendix.
Figure A.1: H.F buoy to receiver data link system.
A.1 Buoy transmitter
The buoy transmitter converts the combined digital data stream which contains the wave height
data, wave spectra, wave direction, seawater temperature etcetera into a high frequency (H.F.)
signal.
Technical details:
The HF output signal of the transmitter is FSK modulated with a rate of 81.92 bits per second in
a bandwidth of 200 Hz and a radiated power of 75 mW (19 dBm). The transmit frequency is
crystal controlled and between 25,5 and 35,5 MHz. (35 – 45 MHz on request).
Trans-
mitter
Buoy Channel Receiver
RX-D2
Data
Natural
noise
Propa-
gation
Wave
height
Distance
Interference
Other trans-
mitters