Products > Test Equipment
Frequency reference clocks should ..
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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