Agilent Technologies 54621A User Manual page 112

Triggering the Oscilloscope
To use TV triggering
To trigger on odd or even fields
To check the envelope of your video signals, or to measure worst case distortion,
trigger on the odd or even fields. When Field 1 is selected, the oscilloscope
triggers on color fields 1 or 3. When Field 2 is selected, the oscilloscope triggers
on color fields 2 or 4.
1 Press the Trigger
More
2 Press the softkey, then press the
Settings
appropriate TV standard.
3 Press the Mode softkey and select
The trigger circuits look for the position of the start of Vertical Sync to determine
the field. But this definition of field does not take into consideration the phase
of the reference subcarrier. When Field 1 is selected, the trigger system will find
any field where the vertical sync starts on Line 4. In the case of NTSC video,
the oscilloscope will trigger on color field 1 alternating with color field 3 (see
the following figure). This setup can be used to measure the envelope of the
reference burst.
Triggering on Color Field 1 Alternating with Color Field 3
3-50
key, then press the
TV
Standard
Field1 or Field2
softkey.
softkey to select the
.