User's Manual

1.1 Health & Safety
Exposure to Non-Ionizing (RF) Radiation/Safe Working Distances
The safe working distance from a transmitting antenna may be calculated from the
relationship:
D =
√
In which D = safe working distance (meters)
PT = transmitter or combiner power output (watts)
GR = antenna gain ratio = anti log (gain dBi ÷10)
w = power density (watts/square meter)
The RF power density value is determined by reference to safety guidelines for exposure of
the human body to non-ionizing radiation. It is important to note that the guidelines adopted
differ throughout the world and are from time-to-time re-issued with revised guidelines. For
RF Central use, a maximum power density limit of 1w/m² is to be applied when calculating
minimum safe working distances. Appendix A refers.
Important Note: It must be remembered that any transmitting equipment radiating power at
frequencies of 100 KHz and higher, has the potential to produce thermal and athermal effects
upon the human body.
To be safe:
a) Operators should not stand or walk in front of any antenna, nor should they allow
anyone else to do so.
b) Operators should not operate any RF transmitter or power amplifier with any of its
covers removed, nor should they allow anyone else to do so.
Worked examples
Antenna Transmitter Power
Type Gain (dBi) Gain Ratio 2W 4W 10W 30W
OMNI
4 2.5 1 1 1.5 2.5
HELIX
20 100 4 5.6 9 15.5
PARABOLIC
DISH
35 3,162 22.5 32 50 87
MINIMUM SAFE DISTANCE (METERS)
PT. GR
4π.w
RFX-RMTC LAST REV: 14 December, 2006 Page 4 of 16