Agilent Technologies 8590 Series Service Manual page 435

Menu 1 of 3
enables the display of the diagnostics data on
DIAGS ON OFF
demod-based measurements along with the measurement results. This
data is shown as a small highlighted block on the screen. The exact
meaning of each of the data items is detailed in the "Diagnostic Data"
section.
enables a mode in which demod-based measurements
IGNORE ON OFF
will ignore any QAM acquisition or measurement failure and show the
measurement anyway. This is useful to observe the constellation under
this condition since it can yield valuable clues about the particular fault
(spinning or random constellation). Note that this only ignores
acquisition or measurement unlocks; it will not ignore a 240 MHz PLL
unlock or level set failure.
enables the following diagnostic and optional control keys
KEYS ON OFF
located elsewhere in the menus.
• is located in the
Service
• and
AGC HOLD RUN
(live) demod-based measurement.
manually enter a value of Option 190 downconverter attenuation
independent of the value set by the level-set algorithm, and display
in the diagnostic data. Useful information can be gleaned by
entering values different than that set by the level-setting
algorithm, then observing the effects on the constellation, or other
measurement.
Note that values are entered "blind" into the keypad, terminated by
; there is no visible active function area on the screen. Note also
dB
that the diagnostic data does not change to reflect the new value of
downconverter attenuation. Also, only even values of attenuation
are utilized, due to only 2 dB steps are available on the board.
(hold underlined) will freeze the AGC loop on the Option
HOLD RUN
190 demodulator input. This allows subtle effects to be observed
without being obscured by the action of the AGC loop.
•
VARIANCE SD 90%
set to SD (SD is underlined), this will make averaged measurements
display the standard deviation instead of the 90% confidence value of
measurement variance.
• located in the
METRIC ON OFF
(on is underlined) will make the SER measurement display the
EVM, or MER, that accompanies the measurement in a manner
identical to the channel response measurements.
Chapter 10
menu.
lq Constln
are shown during a continuous
DNCVRTR ATTEN
DNCVRTR ATTEN
is located in the
Modulation Accuracy
SER, C/N Margin
Analyzer Options and Block Diagrams
Option 190 DVB-C Service Menus
is used to
menu. When
menu, when set to ON
AGC
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