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Frequency reference clocks should ..

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tautech:
FYI
10 MHz Ref Out from a $20k VNA with no OXCO installed. (default internal clock)

Bud:
If you think logically for a sec, you want to lock your receiving device to Fref. You do not want it to lock to 2Fref, 3Fref, etc. Therefore having a clean sine wave Fref makes sense.

TimFox:
Some of my old equipment, internally using a 10 MHz reference, would allow an external signal at 5 or 10 MHz, since it was passed through a narrow-band (probably crystal) filter.
Also, 5 MHz high-stability oscillators were a thing back then.

nctnico:

--- Quote from: Bud on January 26, 2023, 10:19:52 pm ---If you think logically for a sec, you want to lock your receiving device to Fref. You do not want it to lock to 2Fref, 3Fref, etc. Therefore having a clean sine wave Fref makes sense.

--- End quote ---
That is only a problem if you have lots of distortion due to impedance mismatch. First thing that is done to the incoming signal is to turn it into a square wave.

eloso:

--- Quote ---Better, still not great.  I wonder if something is being overdriven here, the output is over 2X the 50mVp-p that is specified.
--- End quote ---

It will look better if you use the 50ohm input of your scope (like you just did) but now  discard your 1M probe. Use a piece of 50ohm cable.   Make sure you don't exceed your scopes max input which will be only a few volts.

Or put a 50ohm external load on the ref signal and then use your 1M probe across the external 50ohm terminator.

Interesting thread !

Eloso

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