Service manual
E-4 MOTOTRBO Base Station/Repeater – EME ASSESSMENT: Typical System Configuration
E.3 Typical System Configuration
The MOTOTRBO MTR3000 Base Station/Repeater operates in the frequency ranges 403–470 MHz
and 470–524 MHz, with up to five channels transmitting 100 W radio frequency (RF) power. The
typical system configuration comprises an omnidirectional array antenna featuring 6–10 dBd gain,
installed at or above 20 m from ground level, and fed by the MTR3000 through a combiner
characterized by a typical 3 dB transmission loss, and a 30 m 7/8” coaxial cable characterized by a
typical 2.7 dB/100m loss at 400 MHz, resulting in a total 3.9 dB transmission loss. Based on these
characteristics, the RF power at the antenna input is about 200 W.
Since shorter antennas provide a conservative EME exposure assessment from equation (1), the
parameters of a typical 6.6 dBd antennas are employed. Such an antenna (e.g., Andrew DB408)
would exhibit a typical elevation beamwidth of about 14 degrees.
E.4 Exposure Limits
Based on the MTR3000 operating frequency range, the most conservative power density limits are
those defined in the ICNIRP guidelines [1]. They are 10.1 W/m
2
for occupational exposure, and 2.02
W/m
2
for general public exposure. They will be used for the EME exposure assessment.
E.5 EME Exposure Evaluation
E.5.1 Exposure in Front of the Antenna
The assessment is based on the following characteristics of the Andrew DB408 antenna:
The compliance boundary distance is computed, from equation (1), as follows:
where S
lim
is the applicable power density limit. For occupational exposure, this equation gives:
while for general public exposure it gives:
E.5.2 Exposure at Ground Level
Since the antenna installation height above ground level in the typical system configuration (20 m) is
larger than either of the compliance boundaries determined in E.5.1, the EME exposure at ground
level is always compliant with the exposure limits defined in the ICNIRP guidelines.
5.710
10
15.26.6
==
+
A
G
WP 200
=
o
360=
δ
mL 7.2
=
δπ
ρ
180
lim
SL
P
=
m
mWm
W
OCC
2.1
360
180
/1.107.2
200
2
=
⋅⋅
=
π
ρ
m
mWm
W
GP
6
360
180
/02.27.2
200
2
=
⋅⋅
=
π
ρ