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Procedure
To automatically set the reference and attenuation level:
1
Press the AMP/SCALE hard key.
2
Press the Auto Scale soft key.
Each time you press this key, both of the Y-axis scale and input attenuation level change to be
optimized with some margin.
To set the reference or attenuation level manually:
1
Press the AMP/SCALE hard key.
2
To set the maximum reference value on the Y-axis manually, complete the following steps:
a
Press the Reference Level soft key.
b
Enter a value by using the numeric keys or the rotary knob with 10 dB increments.
c
Press the dBm soft key or the ENTER hard key.
This unit key name changes according to the setting in the Units menu.
3
To set the attenuation option, select one from the following choices:
–
To set the input attenuator's level automatically, select Attenuation > Auto.
NOTE
It is recommended that you set the Attenuation to Auto in most situations so that the
level of the input attenuator can be set automatically according to your input signal level.
–
To set the input attenuation manually up to 55 dB for JD780B series or 50 dB for JD740B
series to optimize S/N, complete the following steps:
a
b
c
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.
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
Select Attenuation > Manual.
Press the Attenuation Value soft key to set the level.
Enter a value in fives by using the numeric keys.
Press the dB soft key or the ENTER hard key.
JD700B Series User's Guide
Chapter 16 Using Channel Scanner
499
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