Distorted Sine Wave

I copied the wrong yandex.

Try this (29 May 2024): .

Joe Gwinn

And

I did read that, but didn't know what to make of it. I think an annotated drawing is required.

On this drawing, where do the various scope traces mentioned up-thread come from?

Joe Gwinn

Joe, I appreciate you're only trying to help, but don't worry about it. I don't believe the oscillator this thread relates to is causing the PLL unlock error so we've all gone down a bit of a rabbit hole with this one. I really need to look elsewhere for the culprit.

For what it's worth, I found a manual on the web saying that the

Jeroen Belleman

Thanks, Jeroen. It would be a pretty simple matter to provide the analyzer with an external 10Mhz source of that level from an RF signal generator, but as we've both said now, I don't think that's the issue. The service manual only says to investigate boards A19,A20,A21 and A11 - which I have done superficially. But I've just noticed in the Repair & Troubleshooting manual it says A16 should also be checked, so I'll do that next..... Many thanks.

I measured the 10MHz output of my unit with an HP 54542A digital storage 'scope and found the following:

50ohm input via 5m coax

The waveform with 1Mohm load looked like a perfect sine wave, whereas the 50 ohm loaded waveform showed some second harmonic distortion visible as a slight narrowing of the top of the sine and a slight flattening of the bottom of the sine.

The frequency measured with an HP 53131A frequency counter was 10.000199MHz. The spectrum analyzer had been on standby for a few weeks and fully powered for a few hours, so the crystal oven should have been at equilibrium. I then substituted my rubidium oscillator which indicated 9.999997MHz on the counter.

The connector that I used was the one labelled 10MHz at bottom right, not the adjacent reference output which is connected to a reference input with a short coax jumper. Is the same output that you measured?

John

Hi John, sorry for the delay in replying. You got some interesting results there. Not what I'd expected, to be honest. We have to bear in mind that the 8566B is a different beast to yours, of course, so a bit of leeway can be allowed for that. Nevertheless, the fact you're getting a decent sine wave into 1Meg is curious, given what I experienced. I'm taking my 10Mhz from a BNC socket on the rear panel which HP placed there to make it easier to check and adjust the 10.0000000Mhz out as precisely as possible. I'm sure yours