Mike,
    The strobeperiod parameter is not what you want. That turns on strobing for the normal transient or PSS analysis output. Instead, go to the Choose Analysis form for the PSS analysis and set Noise Type to timedomain.  This would result in the noise being displayed as a function of time. This is more than what you need, and is expensive. So set the skipcount to a large value to reduce the number of timepoints at which the noise is evaluated, and add the time you would like the noise to be evaluated to Add Specific Points.

-Ken