User Reference and Installation Guide
3-16
© 2006 Microwave Data Systems Inc. All Rights Reserved.
MDS FOUR.9 Series
05-4561A01, Rev. A
Antenna Gain (External) – 23 dBi = Antenna Gain Difference
37.6 dBi – 23 dBi = 14.6 dB
For mode 100FE1 (single channel configuration with 30MHz emission bandwidth) the power
would be lowered from
Tx Power – Antenna Gain Difference = Tx Power (External Ant)
+5 dBm – 14.6 dB = -9.6 dBm (-10 dBm).
Table 3-1 also presents transmit power settings for various antenna dish sizes.
For link budget, EIRP (Avg) dBm = 37 dBi + Tx Power Setting (dBm).
Table 3-2. Maximum Power Settings for 4.9GHz Public Safety Band Operation (US).
Antenna
Diameter
Antenna
Gain, dBi*
(example)
Maximum Tx
Power
Setting, dBm
EIRP
8 foot dish
39.5
17
56.5
6 foot dish
36.1
21
57.1
4 foot dish
33.1
23
56.1
3 foot dish
30.5
23
53.5
2 foot dish
27.1
23
50.1
* Note: Many antenna manufacturers rate antenna gain in dBd (dB referred to a dipole antenna)
in their literature. To convert to dBi, add 2.15 dB.
Power settings for other modes of operation can be easily extrapolated from Table 3-2. For link
budget calculations,
EIRP (Avg) dBm= Antenna Gain (dBi) + Tx Power Setting (dBm).
Though transmitter radiated power is limited in the 4.9 GHz band regardless of antenna size, the
receiver benefits from gain of larger antennas.
3.6.6.2
6.4 GHz Band
In the 6.4 GHz Fixed Microwave Services band the peak EIRP (Effective Isotropic Radiated
Power) is limited to +55 dBw at the antenna for any bandwidths. 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.
EIRP is calculated for link budget with external antennas as,
Summary of Contents for FOUR.9 Series
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