MTV3- ASUM-7001-07
page 5 of 25
1.4
Health & Safety
Exposure to Non Ionising (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 = maximum allowed 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-ionising 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
Gigawave use, a maximum power density limit (w) of 1w/m² is to be applied when calculating
minimum safe working distances.
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 receiver or power amplifier with any of its covers
removed, nor should they allow anyone else to do so.
Worked examples
Antenna
Receiver 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 (METRES)
P
T
. G
R
4
.w
