I wanted to use the 10 MHz output from a Racal Dana 1992 counter as an external reference for a Siglent SDG1025 function generator, but the output level wasn't high enough, so I made a cute little amplifier.
I also ran into what I think is a firmware bug. After setting the clock source on the SDG1025 to external, restarting it has it using the internal clock again even though the setting is saved and still says "external". Toggling the clock source to internal and back to external works to get it using the external reference again.