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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 00:33:52 +0000 From: boB <boB@K7IQ.com> Newsgroups: sci.electronics.design Subject: Re: Distorted Sine Wave Date: Fri, 31 May 2024 17:33:51 -0700 Message-ID: <60rk5jti9l5154hqaqicohmj3u1lfd16g3@4ax.com> References: <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> <9tok5j9p388ookujrtbsofskjlbekfuhjb@4ax.com> User-Agent: ForteAgent/8.00.32.1272 MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Lines: 166 X-Trace: sv3-iiWIT03VwOUIvluU1SKaMgVBV5DMHXqVcItymrfhB1aj5u0xsygKJMHQ7qLyG2bclCub0pyRtwVJOMz!OBS+aaaGqjxyQIQcnUigDOd3ND5req85Nb4WV+4XGziqgKbI08Z+qduU1y+UfxYzjn4mutVUNMZj!EPzjf0ce 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: 7930 On Fri, 31 May 2024 17:02:13 -0700, boB <boB@K7IQ.com> wrote: >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. I thought I said the wrong thing ! I mean odd harmonic(s) from a non-linearity. > 2nd harmonic is usually due to non 1/2 wave symetry (DC >offset bascially) > Here, I meant even harmonic(s) not just second harmonic. It's rather hot today in Phoenix.. >What was tha amplitude after you loaded it down properly ? How about >a picture ? > >Where were you scoping this at again ? > >boB