ETS-Lindgren 3161 Octave Horn Antenna - Manual (Page 27)

6.0 Radiated Emissions Measurements
Measure Ambient Field Strength Values
1. Install the antenna where measured field strength values are desired.
2. Adjust the desired orientation of the antenna, both bore site direction
and polarization.
3. Connect the output connector of the antenna to the input of the
receiving system using a low VSWR, low loss 50 Ω coaxial cable.
4. Set desired measurement frequency. Make sure that the selected
frequency is one that can be used with the antenna that is connected
to the system.
5. Measure the RF voltage, V
a
, referenced to the input port of the
receiving system. The units of the measurement should be in decibels
referenced to 1 microvolt, dB(µV). If the units of measurements are
millivolts, they should be converted to dB(µV) by:
6. Determine the field strength at the frequency of observation by adding
the voltage reading on the receiving system in dB(µV) to the
antenna factor in dB(m
-1
):
V RF voltage in microvolts
RF Voltage, dB(µV) + Antenna Factor, dB(m -1 ) =
Field Strength, dB(µV/m)
E
a
= V
a
+ AF
The losses of the coaxial cable, A
c
, should be included in the
computations. In this case, the previous equation becomes:
RF Voltage, dB(µV) + Cable Loss, dB +
Antenna Factor, DB(m -1 ) = Field Strength, dB(µV/m)
E
a
= V
a
+ A
c
+ AF
)
V V
a
a d
=
= 20
20
10
10
log (
log
Radiated Emissions Measurements | 27