About Playback Triggering (Input)

The Playback Trigger tab sets up triggering when playing recorded data. The same trigger parameters available when triggering from hardware are available when playing a recording, except for the trigger types and trigger holdoff. The trigger conditions of slope, level, delay, and trigger holdoff share the same operation as their identical parameters under the Input > Trigger tab, with the exception that holdoff is available for all playback trigger types except Freerun. The Display Ref Line on Active Trace selection is available and is identical to the Display Ref Line on Active Trace selection found under the Input > Trigger dialog box.

Playback Trigger is unavailable for Power Spectrum measurements.

When playing a recording, the following trigger types are available: (If a particular trigger type is not available for the recorded data, that type does not appear in the menu.)

Free Run selects free-run triggering. This means that the VSA will process time records as quickly as possible, without waiting for any kind of triggering signal (sometimes called continuous triggering).
Channel triggers the measurement when the real part of the signal changes. The measurement begins when the signal on the selected input channel meets the requirements set by slope, level, delay, and hold-off. Note that although channel trigger is available for all recordings, it is really only useful for baseband data.
Magnitude triggers the measurement when the magnitude of the envelope changes. IF Mag is usually used with amplitude modulated (AM Amplitude Modulation - CW modulation using amplitude variation in proportion to the amplitude of the modulating signal. Usually taken as DSB-LC for commercial broadcast transmissions and DSB-SC for multiplexed systems.) signals. Magnitude trigger triggers the VSA when the playback signal is within the current span AND the playback signal is varying in amplitude AND the trigger conditions (slope, IF Mag level, and delay) are met.

Playback triggering is done from the data before filtering. This is different from Magnitude or IF Mag triggering on data directly from hardware, as shown in the following illustration.

With Magnitude triggering, the magnitude of the playback signal must vary to trigger the VSA. The magnitude of the playback signal varies when it switches on and off or if it is AM modulated.

Playback Trigger and Segmented Recordings

Note the following when using Playback Trigger with Segmented Recordings:

Only the first segment is triggered. Data from the remaining segments is taken starting at the same offset within the segment as the trigger offset of the first segment.
When the trigger is found too close to the end of the segment such that the amount of data needed for a measurement update would cross the segment boundary, the trigger search routine will skip that trigger and start searching at the beginning of the next segment.