Sujet : Re: Distorted Sine Wave
De : cd999666 (at) *nospam* notformail.com (Cursitor Doom)
Groupes : sci.electronics.designDate : 29. May 2024, 23:54:32
Autres entêtes
Organisation : A noiseless patient Spider
Message-ID : <v3886o$1aj2a$1@dont-email.me>
References : 1 2 3 4 5
User-Agent : Pan/0.149 (Bellevue; 4c157ba)
On Wed, 29 May 2024 23:10:56 +0200, Jeroen Belleman wrote:
On 5/29/24 22:49, Cursitor Doom wrote:
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. :)
If this oscillator is made to drive 50 Ohms and you don't provide that,
internal buffer stages may saturate or do other weird things. If it
works OK *with* the 50 Ohm load, then your problem is solved, no?
Jeroen Belleman
Unfortunately not. the suspicion that there was something wrong with that
oscillator was my main hope of an easy fix for this analyzer. Now I have
to go back to the drawing board and start trouble-shooting all over again.
And it's a complex beast!