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FYI I created a photo album and posted a picture of the 33622A ramp displayed on my 11801 using an SD-26 head at 1 ps/div and 2 mV/div with 1024 samples.
With a trigger signal at 100 kHz, you need a ramp at 100.0001 kHz to test the linearity of the time base. I'm just using the internal timebase, the 33622A set as close as I could and taking the photo at the right moment. It took a couple of tries. I'll try for more rigorous results later.
I'd like to thank be_moulton for suggesting the idea. I had pondered the subject, but lacked the insight needed. It's a great pleasure to have such excellent company join us.