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6 Input/Output

6.3 External Gain

6.3 External Gain

Contains controls that allow you to compensate for gain or loss in the measurement

system outside the instrument. The External Gain is subtracted from the amplitude

readout (or the loss is added to the amplitude readout). So, the displayed signal

level represents the signal level at the output of the device-under-test, which can be

the input of an external device that provides gain or loss.

Entering an External Gain value does not affect the Reference Level, therefore the

trace position on screen changes, as do all of the values represented by the trace

data. Thus, the values of exported trace data, queried trace data, marker

amplitudes, trace data used in calculations such as NdB points, trace math, peak

threshold, etc., are all affected by External Gain. Changing the External Gain, even

on a trace that is not updating, immediately changes all of the above, without new

data needing to be taken.

NOTE

Changing the External Gain causes the instrument to immediately stop the

current sweep and prepare to begin a new sweep. The data will not change until

the trace data updates because the offset is applied to the data as it is taken. If a

trace is exported with a nonzero External Gain, the exported data will contain the

trace data with the offset applied.

In Spectrum Analyzer Mode, a Preamp is the common external device providing gain

or loss. In a measurement application mode like GSM or W-CDMA, the gain or loss

could be from a BTS (Base Transceiver Station) or an MS (Mobile Station). So, in the

Spectrum Analyzer mode MS and BTS would be grayed out and the only choice

would be Ext Preamp. Similarly, in some of the digital communications applications,

Ext Preamp will be grayed out and you would have a choice of MS or BTS.

The Ext Preamp, MS, and BS controls may be grayed-out depending on which

measurement is currently selected. If any of the grayed-out controls are pressed, or

the equivalent SCPI command is sent, an advisory message is generated.

6.3.1 External Preamp

This function is similar to the reference level offset function. Both affect the

displayed signal level. Ref Lvl Offset is a mathematical offset only, no instrument

configuration is affected. Ext Preamp gain is used when determining the auto-

coupled value of the Attenuator. The External Gain value and the Maximum Mixer

Level settings are both part of the automatic setting equation for the RF attenuation

setting. (10dB of Attenuation is added for every 10dB of External Gain.)

2189 Vector Modulation Analyzer Mode User's &Programmer's Reference

Keysight x-series Programmer's Reference

Other manuals for Keysight x-series