Datawell 45100, Руководство пользователя

Страница: 26 / 37

26
enough to overdrive the receivers input stages.
6
Identifying an interferer can be done with a
commercial HF receiver for the 20-40 MHz band or with specialized equipment such as a
spectrum analyzer.
Fortunately interferers in general come from one direction only –usually away from the shore-
and it is often possible to use a directional antenna directed at sea so that it more sensitive in the
buoy direction and less sensitive in the direction of the interference source, usually located in
the residential and business areas closest to the buoy receiving site.
Possible error sources and solutions:

Error: an in-band interferer damages my data.
Solutions: use a directional antenna, place the antenna closer to the buoy and/or further
away from the interference source, or choose a different frequency for the link.

Error: an out-of-band interferer damages my data although the buoy signal is strong.
Solutions: use an attenuator
7
at the input of the receiver, use a directional antenna and/or
contact our service department.

Error: an out-of-band interferer damages my data and the buoy signal is weak.
Solutions: use a directional antenna and/or contact our service department.
A.3.4 Propagation
The maximum propagation distance of a radio wave from a 100 mW 30 MHz transmitter over
different types of water, ground and ice (all supposed to be flat) with a receiver capable of
receiving -110 dBm and short ¼ λ vertically polarized antenna’s at 1 m height.
Ground Type 
(S/m)

r
Distance @ 100mW
(km)
Sea water Average salinity 5 70 95
Sea water Low salinity 1 80 47
Fresh water (no salt) 3x10
-3
80 18
Land 3x10
-2
40 14
Ground Wet ground 10
-2
30 12
Land 3x10
-3
22 10
Ground medium dry ground 10
-3
15 7
Ground dry ground 3x10
-4
7 6
Ground very dry ground 10
-4
3 4.5
Fresh water ice -1°C 3x10
-5
3 4.5
Fresh water ice -10°C 10
-5
3 4.5
6
A 27 MHz CB transmitter within 100 m will overload the input stages of commercial HF receivers,
including those of the RX-D2.
7
In the range of 10 up to 50 dB, available from e.g. www.minicircuits.com .