User Manual

MDR2400 and MDR5800 User Manual
862-01881 Issue 8 Page 22
Table 6 MDR2400 Antenna Selection
Antenna Type Gain (dBi) Distance (Km) Power level (dBm)
1.2 m Parabolic
Antenna
27 80 18
3.2 Site Evaluation
When planning a site for a digital radio link, it is of the utmost importance that you
take the operational environment of the proposed site into account.
The combined effect of atmospheric environmental factors such as rain and lightning,
atmospheric attenuation, signal path obstruction, propagation fading, air temperature
gradients, ice build-up, wind and solar radiation can contribute towards reducing the
level of performance of the system. In the higher frequency bands, rainfall is the main
attenuation mechanism that limits error performance. Ice and snow will have a similar
effect. Severely cold and excessively warm climatic conditions outside the scope of
the operating temperature range can affect the function of the system, especially the
outdoor equipment (see Environmental Characteristics on page 65 of this manual).
Also, if masts are not sufficiently rigid, very strong winds can affect the antenna beam
alignment and Outdoor equipment reliability due to wind force build-up and/or vibration
of the mast-mounted equipment.
3.3 Multipath Effects
The MDR digital radio can be influenced by the effects of multipath propagation.
Understanding these effects will help when installing an MDR digital radio link and
maximise the reliability of the link.
Multipath fading occurs when the receiving antenna receives not only the direct signal
from the transmitting antenna but also a signal from the transmitting antenna that has
reflected off the ground or nearby obstacles. The reflected signal takes a longer path
to reach the receiver and acts as interference since it is not in-phase with the direct
path signal. The amplitude of the interference can be almost equal to that of the direct
path signal, thus degrading the performance of the link.
Multipath propagation is dependent on transmit frequency and the specific geometry
of the link such as antenna heights, distance between the antennas and the local
terrain. To counteract multipath propagation, the installer can change the frequency
at which the link operates or adjust the height of one or both of the antennas.
Figure 6. Multipath Effects.
User Data
MDR OU
MDR IU
User Data
MDR OU
MDR IU
Direct RF Path
Reflection Path