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From: Cursitor Doom <cd999666@notformail.com>
Newsgroups: sci.electronics.design
Subject: Re: Distorted Sine Wave
Date: Wed, 29 May 2024 20:49:27 -0000 (UTC)
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On Wed, 29 May 2024 13:42:13 -0700, john larkin wrote:

> On Wed, 29 May 2024 21:43:54 +0200, Arie de Muijnck <noreply@ademu.com>
> wrote:
> 
>>On 2024-05-29 19:07, Cursitor Doom wrote:
>>> Gentlemen,
>>> 
>>> Whilst fault-finding on my HP 8566B spectrum analyzer, I've found the
>>> 10Mhz reference oscillator is generating an 'unsatisfactory waveform'
>>> which may be causing the device to be unable to lock it's main PLL.
>>> I've come across this waveshape before, but mostly with oscillators I
>>> was building and in the process of trying to iron out the wrinkles of
>>> and certainly NOT a critical reference oscillator from a respected
>>> manufacturer. Can anyone tell what's most likely going on here?
>>> 
>>> https://disk.yandex.com/i/z6fYbeVfPRK7aA
>>
>>
>>Looks like reflections in the cable. Try the 50 Ohm termination.
>>
>>Arie
> 
> If the drive is a sine wave, a cable can't generate that 2nd harmonic.

I don't understand how a reflection can account for it either. THe cable's 
only 4' long! However, with the 50 ohm input enabled, the 2nd harmonic 
disappears. It's just one of those inexplicable mysteries that no one 
knows the answer to. :)


> Our boxes output a 10 MHz square wave. Our clock inputs have a 10 MHz
> bandpass filter, so they accept most anything.