@rigrunner: A quick google search turned this up: http://thumbs2.ebaystatic.com/d/l225/m/m7nQNXUOBrRbBYD1ywQbBaw.jpg
@Rufus: I didn't try that, but even AC coupled, wouldn't have that simply reduced the jitter by half (at best)?
I am suggesting there is no jitter on the signal it is just jitter in the scope trigger point because alternate cycles have different amplitudes.
I understood that, my point was that even with the signal AC coupled, the scope would still see some jitter, due to the fact that the middle point would be an average across a big chunk of the signal and not on a per cycle basis, so each cycle's middle point would still be different than the signal's middle point, so the best case scenario would be 1/2 of the original jitter.
Now, if it was indeed an amplitude issue, it's obvious to me that it wasn't symmetric, because I couldn't get a clean waveform no matter what trigger level I used, so for all intents and purposes, the jitter was real.
As for the 50 Ohm termination, I'm still not sure if that's the correct value. This OCXO has clearly been designed to drive low impedance loads, but with out a datasheet it's hard to say what that value should be, especially since it's a custom oscillator and it seems to work fine with a wide range of impedances.
Edit: I ran a little test and it turns out it was 5 MHz AM, just as you said, but AC coupling doesn't make any difference, just as I said