Hi Jim, thanks.
I've just spent some time fishing around the outside of the chassis with a loop probe and the 60 kHz spurious is from the front of the instrument around the display. It isn't a single tone, it is spread over many kHz on the high side of 60 kHz and looks to be caused by digital traffic. It might be the display causing it. It seems to be at 59 kHz and it may be backlight related but it looks like it has some digital traffic on it.?
?
Probing around the screen area of an E5071B VNA (I think this has the same touch screen display) shows exactly the same waveform so it is definitely screen related in some way. I'm not sure how this is getting into the baseband path but because it is also there on the main phase noise display I think it is getting in at the ADC/DSP module, possibly via a power supply rail. Hopefully a tired decoupling cap is the cause.
