Chapter 10 10-17
Service Key Menus and Error Messages
Service Key Menus
.
Table 10-11 Service Modes Menu Keys
Key GPIB
Mnemonic
Description
SM1 Tests the A13 and A14 fractional-N circuits. It allows you to
directly control and monitor the output frequency of the
fractional-N synthesizer (10 MHz to 60 MHz). Set the
instrument to CW sweep mode and then set FRACN TUNE
ON.
Change frequencies with the front panel keys or knob. The
output of the A14 assembly can be checked at A14J1 HI OUT
(in high band) or A14J2 LO OUT (in low band) with an
oscilloscope, a frequency counter, or a spectrum analyzer.
Signal jumps and changes in shape at 20 MHz and 30 MHz
when tuning up in frequency, and at 29.2 MHz and 15 MHz
when tuning down, are due to switching of the digital divider.
This mode can be used with the SRC TUNE mode as
described in
Chapter 7 , “Source Troubleshooting.”
N/A Accesses the functions that allow you to adjust the source:
tests the pretune functions of
the phase lock and source assemblies. Use the entry
controls to set test port output to any frequency from
300 kHz to 6 GHz. When in this mode:
— Set analyzer to CW frequency before pressing
.
— Test port output is 1 to 6 MHz above indicated
(entered) frequency.
— Instrument does not attempt to phase lock.
— Residual FM increases.
allows you to change the source
tune frequency.
toggles the automatic leveling control
(ALC) on and off.
SM3 With this mode switched OFF, the source stays in the pretune
mode and does not attempt to complete the phase lock
sequence. Also, all phase lock error messages are disabled.
The fractional-N circuits and the receiver operate normally.
Therefore, the instrument sweeps, but the source is being
driven by the pretune DAC in a stair-stepped fashion.
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