INTERTEK TESTING SERVICES
Test Report Number: HK08060834-1 Page 32 of 72
FCC ID: T7HCT8015
Company: RTX Consumer Products Hong Kong Ltd. Date of Test: June 24-July 7, 2008
Model: MBU 400
4.9.3 Field Strength Calculation
The field strength is calculated by adding the reading on the Spectrum Analyzer to the
factors associated with preamplifiers (if any), antennas, cables, pulse desensitization and
average factors (when specified limit is in average and measurements are made with
peak detectors). A sample calculation is included below.
FS = RA + AF + CF - AG + PD + AV
Where FS = Field Strength in dBµV/m
RA = Receiver Amplitude (including preamplifier) in dBµV
CF = Cable Attenuation Factor in dB
AF = Antenna Factor in dB
AG = Amplifier Gain in dB
PD = Pulse Desensitization in dB
AV = Average Factor in -dB
In the radiated emission table which follows, the reading shown on the data table may
reflect the preamplifier gain. An example of the calculations, where the reading does not
reflect the preamplifier gain, follows:
FS = RA + AF + CF - AG + PD + AV
Example
Assume a receiver reading of 62.0 dBµV is obtained. The antenna factor of 7.4 dB and
cable factor of 1.6 dB is added. The amplifier gain of 29.0 dB is subtracted. The pulse
desensitization factor of the spectrum analyzer is 0.0 dB, and the resultant average factor
is -10.0 dB. The net field strength for comparison to the appropriate emission limit is
32.0 dBµV/m. This value in dBµV/m is converted to its corresponding level in µV/m.
RA = 62.0 dBµV
AF = 7.4 dB
CF = 1.6 dB
AG = 29.0 dB
PD = 0.0 dB
AV = -10 dB
FS = 62.0 + 7.4 + 1.6 – 29.0 + 0.0 + (-10.0) = 32.0 dBµV/m
Level in mV/m = Common Antilogarithm [(32.0 dBµV/m)/20] = 39.8 µV/m
To Next Page
Loading...