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I recently bought a PTOC32227 OCXO (datasheet) from eBay (secondhand). It is supposed to output a square wave at 10MHz. However, it is a part of a bigger circuit that is not working properly and it seems to me that the failing component may be the OCXO.

I took it apart from the rest of the board, and connected its VS pin to +5V, GND to ground and measured the HF pin with an oscilloscope (left the VC pin not connected). This is the output:

Screenshot 1

Shouldn't it be an square wave? How can I determine then if the OCXO is working properly?

Thank you!

Edit: my oscilloscope BW is 100MHz, so it should not be a problem in the measurement

Edit 2: new measurements with my probe in x10 mode seem fine! Thanks!

New screenshot

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  • \$\begingroup\$ One thing to remember is that a 100MHz scope does only measure up to 100MHz sinusodial signals with a 3dB attenuation. A square wave contains many more harmonica and will therefore look distorted when measured with a too low bandwidth. \$\endgroup\$ – Jakob Halskov Nov 10 '19 at 15:13
  • \$\begingroup\$ @jakob Well, but for this measurement I am using its full BW, and 100MHz should be able to measure well the first harmonics, so that the wave looks more like a square, isn't it? \$\endgroup\$ – user3141592 Nov 10 '19 at 15:17
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    \$\begingroup\$ Are you driving the 'scope input directly through a coax cable? Or perhaps you're using a X1 probe position? The coax capacitance may give you grief. Try a 10X probe. \$\endgroup\$ – glen_geek Nov 10 '19 at 15:28

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