38 Chapter 2
Instrument Functions: A - L
AMPLITUDE / Y Scale
Instrument Functions: A - L
Key Path: AMPLITUDE / Y Scale
Dependencies/
Couplings: This function is not available (grayed out) if:
• the microwave preselector is off. (See Input/Output, Microwave
Preselector
.)
• external mixing is selected and Mixer Type is unpreselected.
• the frequency range is entirely within band 0 (0 Hz to ~3.05 GHz).
History:
Modified in revision A.06.00.
Remote Command:
[:SENSe]:POWer[:RF]:PCENter
Remote Command Notes: This command is sent in a non-preselected band, or the active
marker is less than 3 GHz, an error message is sent.
Example: POW:PCEN
2.1.6 Presel Adjust
Allows you to manually adjust the preselector filter center frequency to optimize its
response on the signal of interest. This function is not available in frequency band 0. It is
for signals
≥2.85 GHz in band 1 and higher. And it is not available if the preselector is
turned off. The key also accesses the menu to choose the desired preselector.
For general purpose signal analysis, using
Presel Center is recommended. Centering the
filter minimizes the impact of long-term preselector drift.
Presel Adjust can be used instead
to manually optimize the preselector. One application of manual optimization would be to
peak the preselector response, which both optimizes the signal-to-noise ratio and
minimizes amplitude variations due to small (short-term) preselector drifting.
The analyzer can contain more than one preselector. E4446A and E4448A analyzers both
have 3-26.5 GHz preselector bands and >26.5 GHz preselector bands. The adjustment is
preselector specific and the analyzer stores a value for each preselector. Therefore, when
the desired frequency range includes frequencies both below and above 26.5 GHz, you
must center and adjust each preselector.
The key readout shows which preselector will be adjusted when the key is pressed. The
choices are [3-26 GHz], [26-50 GHz], and [External]. After performing a
Presel Center, the
value that is shown on the
Presel Adjust key is the offset from nominal of the affected
preselector’s frequency.
With
Presel Adjust selected, press the key again to access the preselector selection menu to
select the preselector you wish to adjust. Some instrument settings will force a preselector
selection. The following flowchart shows the conditions that cause the preselector selection
to change:
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