User Manual

MDR2400 and MDR5800 User Manual
862-01881 Issue 8 Page 23
3.4 Interference Considerations
The ISM frequency bands are used by devices that can cause interference to the
MDR radio systems. Interference can be avoided by careful planning of the system
installation. The available methods for providing isolation from interfering radiators
are the following:
• Frequency diversity
• Antenna polarisation
It is recommended to scan the proposed installation areas (spectrum analyzer) to
establish the presence of interference. The frequency spectrum should be scanned
over a sufficient time period to ensure that periodic transmissions are recorded.
Interferers will cause problems if their amplitudes are not more than 20 dB below the
intended receive power level. A link path loss calculation should be performed to
determine the expected receive power level.
The procedure for selecting the optimum antenna polarisation and system frequency
plan is the following:
• Perform a spectral analysis at each site in the link direction using a high gain
antenna.
• Repeat the spectral analysis for vertical and horizontal polarisation.
• Select the polarisation with the lowest interfering levels as the system antenna
polarisation.
• Consult the MDR frequency channel plans as shown in section 2.2.1 and
select the frequency plan that would operate in an interference-free band.
• Install the ‘High Band’ and ‘Low Band’ Outdoor Units at the sites where they
would experience the lowest interference in their respective receive bands.