User Manual

MDR5800 User Manual
862-01881 Issue 6 Page 21
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 64 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 MDR5800 digital radio operates at frequencies close to 5.8 GHz and can be
influenced by the effects of multipath propagation. Understanding these effects will
help when installing an MDR5800 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 4. Multipath Effects.
User Data
MDR5800 OU
MDR5800 IU
User Data
MDR5800 OU
MDR5800 IU
Direct RF Path
Reflection Path