User Reference and Installation Guide
3-15
© 2006 Microwave Data Systems Inc. All Rights Reserved.
MDS FOUR.9 Series
05-4561A01, Rev. A
Only directional antennas can be used with the radios. Consult factory for antenna manufacturer
options.
1. Select where the cable will enter the building from the outside.
2. Determine the length of cable required. Allow three extra feet on each end to allow for strain
relief, as well as any bends and turns.
3.6.6
ODU Transmit Power Setup
Setting the ODU transmit power is conditional on the band and application. The installer of
this equipment is responsible for proper selection of allowable power settings.
If there are
any questions on power settings refer to your professional installer in order to maintain
the FCC legal ERP limits.
The SDIDU
TM
employs spectrally efficient shaped Quadrature Amplitude Modulation (QAM). This
waveform is not a constant envelope waveform. Therefore, the average power and peak power
are different. The difference in peak and average power depends on the constellation type and
shaping factor, where spectral efficiency such as more constellation points or lower shaping
factor leading to peak powers higher than average powers. The peak power is typically 5-7 dB
greater than the average power in the SDIDU
TM
, and never exceeds 7 dB. Regulatory
requirements are usually based on peak EIRP which is based on peak power and antenna gain.
3.6.6.1
4.9 GHz Band
In the 4.9 GHz Public Safety band the peak EIRP (Effective Isotropic Radiated Power) is limited
to +57.8 dBm at the antenna for bandwidths up to 15 MHz and is reduced for narrower
bandwidths in accordance with FCC Part 90.1215. The ODU must therefore be adjusted so that
the station does not exceed the allowable limit.
The installer is responsible during set up of transmit power to not exceed FCC limits on
transmission power. These maximum power levels are provided in Table 3-2 for various antenna
configurations, along with the operational bandwidths.
Note that though regulatory limits are stated in terms of peak power, the system transmit power
levels are calibrated as averaged power readings. Average power is used for link calculations.
Therefore the levels provided in table 3-2 are average power levels that have been certified to
correspond with the maximum peak EIRP allowed.
EIRP is calculated for link budget with external antennas as,
EIRP(avg) dBm = External Antenna Gain (dBi) + 23 dBm
3.6.6.1.1
ODU with External Antenna
When using external antennas with gains greater than 23 dBi, the transmit power must be
reduced in dB from that given in Table 3-1 by the antenna gain difference above 23 dBi for the
mode that is being used.
For example, using a 6-foot dish antenna with 37 dBi gain, the output power would be dropped by
Summary of Contents for FOUR.9 Series
Page 2: ......