HP 8920A, User Manual

Page: 273 / 658

273
Chapter 8, Signaling Decoder Screen
AMPS-TACS, NAMPS-NTACS Decoder
Data (hex)
(AMPS-TACS)
This display field lists the decoded data serially as it is received. This field is
labeled
RECC Data (hex)
for the NAMPS/NTACS mode, but performs the
identical function.
Gate Time
This field specifies how long the decoder analyzes a signal after it has been
triggered. The longer the gate time, the greater the number of bits analyzed.
Operating Considerations
If the gate time is too long, the decoder’s data buffer becomes full. A message is
displayed instructing you to decrease the gate time.
This function is not used with the NAMPS/NTACS RVC decoder.
See Also
Arm Meas field description, on page 272
Num of Bits
field description, on page 274
Input Level
This field specifies the expected data signal level (after de- emphasis if used). The
higher the level of signal expected by the analyzer, the higher the trigger level is
set.
Operating Considerations
The unit-of-measure is determined by the
AF Anl In
setting.
The input level should be set high enough to prevent false triggering, but low
enough to allow triggering for valid signals. This you to set the input level well
below the expected level.
Also, when using de-emphasis, the
Input Level
setting may need to be reduced
significantly to properly decode the incoming signal. De-Emphasis is enabled/
disabled using the
De-Emphasis
field on the AF ANALYZER screen.
See Also
Trig Level
field description, on page 275