Path: ...!Xl.tags.giganews.com!local-2.nntp.ord.giganews.com!nntp.supernews.com!news.supernews.com.POSTED!not-for-mail
NNTP-Posting-Date: Sat, 01 Jun 2024 00:02:15 +0000
From: boB <boB@K7IQ.com>
Newsgroups: sci.electronics.design
Subject: Re: Distorted Sine Wave
Date: Fri, 31 May 2024 17:02:13 -0700
Message-ID: <9tok5j9p388ookujrtbsofskjlbekfuhjb@4ax.com>
References: <v38973$1atf2$1@dont-email.me> <3lcf5jd7li0a3c0fgddt7o8lnfocvls2pr@4ax.com> <48bd78e1-7da8-3bba-2879-d22962203fa3@electrooptical.net> <9olh5j9al34fhrebr4grqq8h6c8javjpp1@4ax.com> <seth5jlmgu2gv6lr61m31jk2q94073rvtk@4ax.com> <1n0i5jh257hiinlj2dhaatlo11s33m5n0e@4ax.com> <9k2i5jpfhu3ncfpm28ukusrok4hugal80s@4ax.com> <c6rj5j1l1gfoskul3nnvudf3nc57017k84@4ax.com> <v3d6ce$2anif$2@dont-email.me> <m38k5jlbqo39gr9223b0vg93e8lrbrpurr@4ax.com> <v3dg3k$2anif$3@dont-email.me>
User-Agent: ForteAgent/8.00.32.1272
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Transfer-Encoding: 7bit
Lines: 153
X-Trace: sv3-JuSuMuFncdlCFu4UyHNbeZHj0LyKV+vg+fa2gPd2tA/6n8DAiGx9jx3SheE1YImINtRTf93HHHvHham!HgtGOknKY7zA2bHMtjglY0uP4pcMOTu8zNdnMYC6BaZs2e4PC+YKPvKXzD7FQfHWBOn/R2jnk6m8!3fhv9YCD
X-Complaints-To: www.supernews.com/docs/abuse.html
X-DMCA-Complaints-To: www.supernews.com/docs/dmca.html
X-Abuse-and-DMCA-Info: Please be sure to forward a copy of ALL headers
X-Abuse-and-DMCA-Info: Otherwise we will be unable to process your complaint properly
X-Postfilter: 1.3.40
Bytes: 7505

On Fri, 31 May 2024 21:40:04 -0000 (UTC), Cursitor Doom
<cd999666@notformail.com> wrote:

>On Fri, 31 May 2024 15:10:32 -0400, Joe Gwinn wrote:
>
>> On Fri, 31 May 2024 18:54:06 -0000 (UTC), Cursitor Doom
>> <cd999666@notformail.com> wrote:
>> 
>>>On Fri, 31 May 2024 11:34:46 -0400, Joe Gwinn wrote:
>>>
>>>> On Thu, 30 May 2024 16:24:25 -0700, john larkin <jl@650pot.com> wrote:
>>>> 
>>>>>On Thu, 30 May 2024 18:53:29 -0400, Joe Gwinn <joegwinn@comcast.net>
>>>>>wrote:
>>>>>
>>>>>>On Thu, 30 May 2024 14:56:30 -0700, john larkin <jl@650pot.com>
>>>>>>wrote:
>>>>>>
>>>>>>>On Thu, 30 May 2024 16:06:47 -0400, Joe Gwinn <joegwinn@comcast.net>
>>>>>>>wrote:
>>>>>>>
>>>>>>>>On Thu, 30 May 2024 15:02:44 -0400, Phil Hobbs
>>>>>>>><pcdhSpamMeSenseless@electrooptical.net> wrote:
>>>>>>>>
>>>>>>>>>On 2024-05-29 18:59, Joe Gwinn wrote:
>>>>>>>>>> On Wed, 29 May 2024 22:11:47 -0000 (UTC), Phil Hobbs
>>>>>>>>>> <pcdhSpamMeSenseless@electrooptical.net> wrote:
>>>>>>>>>> 
>>>>>>>>>>> Cursitor Doom <cd999666@notformail.com> 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. :)
>>>>>>>>>>>
>>>>>>>>>>> That?s pretty diagnostic. There must be an LC filter on the
>>>>>>>>>>> output?mis-terminating it will cause all sorts of
>>>>>>>>>>> frequency-response whoopdedoos.
>>>>>>>>>> 
>>>>>>>>>> It also occurs to me that if there is a diode in series with a
>>>>>>>>>> resistor somewhere, the impedance presented to the feed coax may
>>>>>>>>>> be 50 ohms for positive input voltage, and say 10 Kohm for
>>>>>>>>>> negative.  At the very least one could get an inverted
>>>>>>>>>> reflection on negative.
>>>>>>>>>> 
>>>>>>>>>> Joe Gwinn
>>>>>>>>>> 
>>>>>>>>>Yeah, or an emitter follower.  Good point.
>>>>>>>>
>>>>>>>>Plus some LC filter wiggles, to distort and smooth things.
>>>>>>>>
>>>>>>>>I dug around and found a copy of the HP 8566B spectrum analyzer
>>>>>>>>service manual.  The 10 MHz ref input is an amplifier driving a
>>>>>>>>mixer,
>>>>>>>>with not hint of for instance a TTL input.  So, the problem must be
>>>>>>>>elsewhere.  Or, it's just busted.
>>>>>>>>
>>>>>>>>.<chrome-extension://efaidnbmnnnibpcajpcglclefindmkaj/https://
>>>xdevs.com/doc/HP_Agilent_Keysight/
>>>HP%208566B%20Troubleshooting%20&%20Repair%20Vol.%201.pdf>
>>>>>>>>
>>>>>>>>Joe Gwinn
>>>>>>>
>>>>>>>334 pages! Where is the issue?
>>>>>>
>>>>>>The pagination was unclear, so I didn't see a way to say.  How I
>>>>>>found it was to look at the schematics.  Look for module A22.  Don't
>>>>>>think search works on such images, but visual search didn't take that
>>>>>>long.
>>>>>>
>>>>>>Joe Gwinn
>>>>>
>>>>>Too much work for free consulting.
>>>> 
>>>> I took another look.  There is a page reference on the right edge,
>>>> near the bottom, which is not marked as a page X of Y, but is.
>>>> 
>>>> Anyway, look at pages 59 and 77.  At 77, look for A22 in the lower
>>>> left region.  Just above, look for INT and EXT jacks.  The EXT jack is
>>>> where an external reference enters.
>>>> 
>>>> Joe Gwinn
>>>
>>>It's just a block diagram of the reference oscillator module. There's no
>>>detailed schematic of the oscillator itself. At least that's the case
>>>with the PDF version of the Service Manual I have.
>> 
>> It's probably in the book that I don't have, if it was ever released.
>> 
>> Joe Gwinn
>
>HP actually published at least 5 manuals of various kinds about this 
>analyzer, so it's possible it's in one of the others. However, the actual 
>service manual is where I'd expect to find it if they published it at all.
>The other titles are:
>
>HP 8566B Operator's Manual
>HP 8566B Installation and Verification Manual
>HP 8566B Test and Adjustments Manual
>HP 8566B Troubleshooting and Repair Manual
>
>So if the answers are not in *any* of the above, it'd be jolly rotten luck 
>indeed!



Looking at that waveform again...

Could it be that the wavform you are seeing there is not a harmonic
but just a partial cancelation due to reflections ?

If you look at one peak vs. the other, they look about the same time
to me.  About 1 scope division.  Just the amplitude looks different on
alternating cycles.   A non-linearity I would think would make an even
harmonic.  2nd harmonic is usually due to non 1/2 wave symetry (DC
offset bascially)

What was tha amplitude after you loaded it down properly ?  How about
a picture ?

Where were you scoping this at again ?

boB