Hi Paul,
Thank you for the feedback.
Currently through the standard software interface it is only possible to set a period with the ARB setup. This may not be practical for you unless you know how to generate your waveform though. With the ARB setup, you can select a period for your waveform up to 64k samples. So the period length would be limited by the sample rate. We have had another request for this functionality, so I believe we will be adding the period parameter to the standard modulation setup in the near future.
Regards,
A.J.