Occupied Bandwidth
A common measurement performed on radio transmitters is that of occupied bandwidth
(OBW). This measurement calculates the bandwidth containing the total integrated power
occupied in a given signal bandwidth. There are two different methods of calculation de-
pending on the technique to modulate the carrier.
Percent of Power Method
The occupied frequency bandwidth is calculated as the bandwidth containing the specified
percentage of the transmitted power.
XdB Down Method
The occupied frequency bandwidth is defined as the bandwidth between the upper and
lower frequency points at which the signal level is
X
dB below the peak carrier level.
Required Equipment
q
Site Master S332D
q
Portable antenna for the selected signal frequency
Procedure
Step 1.
Connect the antenna to the Spectrum Analyzer connector.
Step 2.
On the Site Master, press the
MODE
key, use the Up/Down arrow key to select
the
Spectrum Analyzer
mode and press
ENTER
.
Step 3.
Press the
FREQ/DIST
key, select the frequency for the measurement by using
Center
and
Span
soft keys, the
Start
and
Stop
soft keys or the
Signal Standard
and
Select Channel
soft keys.
Step 4.
Press the
AMPLITUDE
key and select the
Ref Level
soft key to set the appropri-
ate reference level.
Step 5.
Select the
Atten/Preamp
soft key to set the input attenuation level to automatic,
manual or dynamic.
Step 6.
Press
Preamp On/Off
or
Preamp Auto
to activate the preamplifier manually or
automatically. The default preamplifier mode is auto.
Step 7.
Press the
Back
soft key to return to the previous menu.
Step 8.
Select the
Scale
soft key to set the scale. Choose a value from 1dB/div to 15
dB/div and press
ENTER
.
Step 9.
Press the
MEAS/DISP
key and select the
Bandwidth
soft key to set the resolu-
tion bandwidth and video bandwidth automatically or manually. Press the
Back
soft key to return to the previous menu.
Step 10.
Press the
Measure
soft key and press the
OBW
soft key. Select the measurement
method (dB Down or % of Power) by pressing the
Method
soft key. The cur-
rently selected method is shown in the lower left of the status window.
Step 11.
Press the dBc or % soft keys to adjust the settings as appropriate.
Step 12.
Press the
Measure
soft key to initiate the measurement.
5-10
Chapter 5 Spectrum Analyzer Measurements