2
2 Operating
in
Safety
Guidelines for safe operation are derived from OET bulletin 65, August 1997, as recommended
by the Federal Communications Commission (FCC).
WARNING
High levels of RF power are present in the unit. Exposure to RF or microwave power
can cause burns and may be harmful to health. Remove power from the unit before
disconnecting any RF cables and before inspecting damaged cables and/or antennas.
Avoid standing in front of high gain antennas (such as a dish antenna) and never look
into the open end of a waveguide or cable where RF power may be present.
The HDX-1100, operated without an antenna will not create RF energy exceeding 1.0 mW/cm
2
,
the FCC limit for exposure. Connecting an antenna to the unit greatly enhances the potential for
harmful exposure, and you must maintain a certain distance from the radiator. The following
table shows the Maximum Permissible Exposure (MPE) safe distances from the antenna.
Antenna Gain (dB1)
0
2
3
5
11
Safe Distance (cm)
4
6
6
8
15
Safe Distance (in)
1.57
2.36
2.36
3.15
5.9
Note
Hazardous RF radiation limits and recommended distances may vary by
country. Observe all applicable state and federal regulations when using this
transmitter.
To perform calculations to understand the safe exposure margin (MPE), use the following
formula suggested by OET 65. The calculations provided are for common antennas often used
in the mobile microwave environment.
Calculating MPE
EIRP = P * (10 ^ (G / 10)) = (antilog of G/10) * P
P = RF power delivered to the antenna in mW
G = Power gain of the antenna in the direction of interest relative to an isotropic radiator
R = distance to the center of radiation of the antenna in centimeters
S = MPE in mW/cm² (milliwatts per square centimeters)
Conversions
dBi to numeric gain = Antilog (dBi/10)
Feet to centimeters = Feet * 30.48
Centimeters to Feet = cm * .0328
4
π
= 12.57
User Input
RF power delivered to the antenna = Watts
Antenna gain (referenced to isotropic antenna) = dBi
Distance from the center of radiation = Feet
Calculation steps:
1. [P] RF power input. Watts to milliwatts = Watts * 1000
2. [G] Antenna gain dBi. Numeric gain = Antilog (dBi/10)
3. [EIRP] Multiply P * G
