114 Chapter2
Making Measurements
Example 9: Adjacent Channel Power Measurement
DETECTION:
RMS VOLTAGE
(POWER DETECTOR)
NOTE Power detection is invoked during adjacent channel power calculations
but is not available as a detector mode.
In addition to the warning message, the instrument-state parameter
that is causing the warning will be displayed. The instrument-state
messages that may be displayed are:
• RBW ≥ 300 kHz
• VBW < 10 × RBW
• DETECTOR MODE
• MIN HOLD
• MAX HOLD
• VIDEO AVERAGE
Even though a warning message with an invalid instrument-state
parameter was indicated, the measurement is still made and the
results are displayed in the active function area. If an invalid
instrument-state parameter is suspected, the warning message can be
viewed briefly by pressing
ACP COMPUTE repeatedly. Computation
results without rms detection can be accurate if the signals in the
adjacent channels are similar to continuous wave (CW) signals, but not
if the signals are noise-like. Also, some international standards for ACP
measurements require the video bandwidth to be equal to the
resolution bandwidth, which prohibits rms detection, while requiring
the measurement to respond to the rms sum of all signals in the
passband. If the video bandwidth is set according to this standard, the
warning message will be displayed.
In addition to the warning messages for invalid instrument-state
parameters listed above, the following three error messages may be
observed in the lower right corner of the display:
• ERR 908 BW>>SPCG indicates that the channel bandwidth is too
wide, compared to the channel spacing, for a valid computation.
• ERR 909 SPAN<ACP indicates that the frequency span is too narrow
to obtain a valid measurement.
• ERR 910 SPAN>ACP indicates that the frequency span is too wide,
compared to the channel bandwidth, to obtain an accurate
measurement.
If any of the three errors occur, the measurement is not completed. To
correct the measurement, adjust your instrument state settings
depending on the error that has occurred.
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