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d.
–
To couple the input attenuator's level with your reference level setting, select Attenuation >
Couple.
As you increase the reference setting, the attenuation level also increases acoordingly.
Optional. To change the scale unit:
1.
Select More (1/2) > Units.
2.
Select the unit of the display scale: dBm, dBV, dBmV, dBµV, V, or W.
The scale unit on the screen changes accordingly.
NOTE
This Units menu is available in the Spectrum and RF Analysis modes.
Scale per division
You can use the Scale/Div feature available for the spectrum and RF analysis. It represents the value
of one division on the horizontal scale. The default setting is 10 dB per division and the maximum
value can be set up to 20 dB.
Procedure
1.
Press the AMP/SCALE hard key.
2.
Select More (1/2) > Scale/Div.
3.
Enter a value between 1 and 20 by using the numeric keys.
4.
Press the dB soft key to complete the entry.
Pre-amplifier
You can turn the internal pre-amplifier on to correct and compensate for the gain of the preamp so that
amplitude readings show the value at the input connector.
Procedure
1.
Press the AMP/SCALE hard key.
2.
Toggle the Preamp soft key and select On or Off as needed.
NOTE
You can turn the Preamp on when the input attenuation range is from 0 dB to 10 dB. If
the attenuation value is manually set to greater than 10 dB, the instrument will
automatically turn off the pre-amplifier to display low-level signal properly on the chart.
External offset
You can turn the External Offset on and manually set the external offset value. An offset consists of a
cable loss and a user offset and the measurement result shows the value reflecting both offset values.
When the external offset value is set at 40 dB in the Spectrum mode, the measurement result
compensates 40 dB at both the Spectrum Analyzer and Signal Analyzer modes.
Procedure
To set the external offset:
Press the dB soft key or the ENTER hard key.
Using GSM/GPRS/EDGE Signal Analyzer
JD780A Series Analyzers
127
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