Agilent Technologies 8590 Series Service Manual page 438

Analyzer Options and Block Diagrams
Option 190 DVB-C Service Menus
Diagnostic Data
When
DIAGS ON OFF
measurements will include the display of extra diagnostic data in a
small highlighted block on the screen.
The format is: XX dB YY,Z ABCD where:
XX is the amount of dB set on the Option 190 downconverter
assembly after the automatic level setting algorithm has run. This
will be an even number from 0 to 60 dB.
YY is the final AGC (signal) reading from the Option 190
demodulator input stage in hexadecimal after the automatic level
setting algorithm has run. This will be 80 (128 decimal) or slightly
more than this. The target for the algorithm is 80 to 82.
Z is a number that indicates the sequence of action taken by the
algorithm. There are 6 possible values:
0: the initial AGC reading indicated no adjustment in was
needed. This should rarely happen since we intentionally set the
gain equation for the initial amount of attenuation to always
make it excessive to guarantee under-drive at the demodulator
input.
1: The initial AGC reading indicated excess attenuation of less
than 12 dB. The attenuation was reduced by this amount and a
subsequent AGC reading indicated the signal was within the
target. This is the most common case.
2: The initial AGC reading indicated excess attenuation of less
than 12 dB. The attenuation was reduced by this amount and a
subsequent AGC reading indicated adjustment was still required
(but less than 12 dB). The attenuation was reduced again by the
required amount and a final AGC reading was taken. This is the
next most common case.
3: The initial AGC reading indicated excess attenuation of 12 dB
(or more). The attenuation was reduced by 12 dB and a
subsequent AGC reading indicated the signal was within target.
This will rarely happen.
4: The initial AGC reading indicated excess attenuation of 12 dB
(or more). the attenuation was reduced by 12 dB and a
subsequent AGC reading indicated adjustment was still required
(but less than 12dB). The attenuation was reduced again by the
required amount and a final AGC reading was taken. This is rare,
but possible (if the downconverter has more loss than "usual").
Note that this case doesn't check the final reading and reduce the
attenuation a third time if the target is not reached. So the level
may not be optimum.
438
in the
Service Menus
is set to ON, demod-based
Chapter 10