[time-nuts] PN/AM and 1.5Hz spur from frequency doubling?

[Anders Wallin]

I'm seeing +20-30 dBc/Hz of excess AM/PN, as well as a strong 1.5 Hz spur
created by frequency doubling from 5 MHz to 10 MHz.
https://goo.gl/photos/GFx9tQoxrSmyzUQo8
The input amplitude to the doubler should be just above the recommended 11
dBm.
What's going on??

thanks!
Anders