Hi Mike,
The trigger input port on the SA44B is now solely used for the tracking generator synchronization. There is not external trigger support in zero-span for the SA devices, only for the BB60 and SM200 analyzers. I apologize for the confusion. Ideally we would grey that option out in zero-span mode for the SA devices. As per the product manual, there was triggering functionality in our legacy software, but it was extremely limited and had lots of stability issues.
I apologize for the inconvenience.
Regards,
Andrew