-120dBc/Hz at 1 Hz is way better than anything I've experienced. I had a look at a plot of my homebrew oscillator and it managed -116dBc/Hz at 10 Hz.? Pretty lame by comparison...
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I guess you are aware of the Jeremy Everard paper from the University of York. This describes a 10 MHz ultra low noise oscillator that achieves -122dBc/Hz at 1 Hz offset.
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They used a Symmetricom 5120A as below. Very impressive! I don't think the E5052A can get anywhere near this level of performance.
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