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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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