From: invalid@invalid.invalid   
      
   "john larkin"  wrote in message news:l5l6hk   
   3ssdvsnumf19sf6t0jrmtjop0im@4ax.com...   
   > On Tue, 11 Nov 2025 18:38:15 +1100, Bill Sloman    
   > wrote:   
   >   
   >>On 11/11/2025 6:51 am, john larkin wrote:   
   >>> On Sun, 9 Nov 2025 18:13:52 +1100, Bill Sloman    
   >>> wrote:   
   >>>   
   >>>> On 9/11/2025 4:36 am, Edward Rawde wrote:   
   >>>>> "Bill Sloman"  wrote in message news   
   10emofm$2cnh3$2@dont-email.me...   
   >>>>>> On 8/11/2025 7:44 am, Liz Tuddenham wrote:   
   >>>>>>> Bill Sloman  wrote:   
   >>>>>>>   
   >>>>>>>> On 8/11/2025 1:46 am, Liz Tuddenham wrote:   
   >>>>>>>>> Bill Sloman  wrote:   
   >>>>>>>>>   
   >>>>>>>>>> On 7/11/2025 9:24 pm, Liz Tuddenham wrote:   
   >>>>>>>>>>> Bill Sloman  wrote:   
   >>>>>>>>>>>   
   >>>>>>>>>>>> On 7/11/2025 10:41 am, john larkin wrote:   
   >>>>>>>>>>> [...]>   
   >>>>>>>>>>>>> A real inductor is a nightmare. Especially a long solenoid.   
   Every turn   
   >>>>>>>>>>>>> inductively couples to every other turn with all possible   
   coupling   
   >>>>>>>>>>>>> coefficients. Distributed capacitances will be similarly complex.   
   >>>>>>>>>>>>   
   >>>>>>>>>>>> This is ignorant nonsense.   
   >>>>>>>>>>>   
   >>>>>>>>>>> I suspect the ignorance is yours.   
   >>>>>>>>>>>   
   >>>>>>>>>>> I worked for a company that built its reputation on the R.F.   
   inductors   
   >>>>>>>>>>> it designed; these factors were among the many problems they   
   tackled.   
   >>>>>>>>>>   
   >>>>>>>>>> Probably not very well.   
   >>>>>>>>>   
   >>>>>>>>> What makes you say that about a leading radio company that I haven't   
   >>>>>>>>> even identified.   
   >>>>>>>>   
   >>>>>>>> I spent 22 years in England in the high tech end of the UK electronic   
   >>>>>>>> business, and the understanding of the wound components they used was   
   >>>>>>>> never impressive.   
   >>>>>>>   
   >>>>>>> Just because the company you worked for didn't understand inductors, it   
   >>>>>>> doesn't exclude the possibility that other companies did understand   
   >>>>>>> them.   
   >>>>>>   
   >>>>>> I spent three years at EMI Central Research. Some of their emplpoyees   
   did get stuff wrong, but they were very high level   
   >>>>>> misunderstandings.   
   >>>>>> I got the staff briefing on their nuclear magnetic resonance imaging   
   system, and asked them why they weren't using   
   >>>>>> super-conducting magnets, and got told that that was a naive question.   
   >>>>>>   
   >>>>>>>>>> The English language text books I could find ...   
   >>>>>>>>>   
   >>>>>>>>> What is the relevance of that?   
   >>>>>>>>   
   >>>>>>>> It makes a point about the local culture. Kibble and Rayner's "Coaxial   
   >>>>>>>> AC Bridges" had some great stuff about wound components, but   
   >>>>>>>> interwinding capacitance was treated pretty superficially.   
   >>>>>>>   
   >>>>>>> How does that support your contention that an unnamed company, that   
   >>>>>>> built its reputation on the excellence of its R.F. inductors,  didn't   
   >>>>>>> design them very well?   
   >>>>>>   
   >>>>>> John Larkin doesn't understand what he is doing all that well,but if   
   you keep experimenting and testing for long enough you   
   >>>>>> can   
   >>>>>> come up with pretty impressive products. Not as good as they could be -   
   but quite good enough.   
   >>>>>   
   >>>>> You don't seem to be interested in providing information which would   
   lead to better products Bill.   
   >>>>> You seem to be much more interested in telling other people how stupid   
   they are   
   >>>>> for only designing products which are "quite good enough".   
   >>>>>   
   >>>>> The circuit below is not good enough in my view but you didn't seem to   
   be able to handle any   
   >>>>> criticism of it some time ago.   
   >>>>   
   >>>> Since it comes from the early part of a very long thread, and since I   
   >>>> subsequently posted variations which performed a whole lot better, I   
   >>>> seem to have been able to handle well-informed criticism pretty well.   
   >>>>   
   >>>> JM was a whole lot more helpful than you were.You did post a variation   
   >>>> of one of his circuits which managed to use eight transistors in the   
   >>>> adjustable gain section - which he promptly cut down to four, and I   
   >>>> subsequently increased to five which got us up to 150db suppression of   
   >>>> the higher harmonics   
   >>>   
   >>> You can Spice -150 dB as a parlor game, but you'll never build   
   >>> anything that good. Opamps won't do it. Thermals won't allow it. Not   
   >>> even real capacitors or resistors.   
   >>   
   >>JM claims to have done. Jim Williams seem to have got better than -120dB   
   >>on the bench with FET gain control Thermal effects are slow and won't   
   >>generate harmonics. Low temperature coefficient resistors don't generate   
   >>much in the way of harmonics. You'd have to be picky about your   
   >>capacitors. Some plastic film capacitors don't present much of a   
   >>problem with charge soak and other non-linear effects.   
   >   
   > Semiconductors have short thermal time constants. Opamps have internal   
   > nodes with tens-of-millisecond time constants and nonlinear junctions   
   > everywhere.   
   >   
   > Most Spice opamp models are behavioral, nothing like realistic.   
   >   
   > Resistors have thermal time constants and especially have voltage   
   > coefficients; the very best are a few PPM/volt and most are far worse.   
   >   
   > Caps are nonlinear for lots of reasons.   
   >   
   > But you'll never build your oscillator and would have no way to test   
   > it for sub-PPM distortion.   
   >   
   >   
   >>   
   >>I'd go for polypropylene film parts. One of the engineers I'd worked   
   >>with had used Teflon film capacitors in a project where this was a   
   >>problem - he talked about in his job interview with me, and it did   
   >>convince me that we ought to hire him. I wasn't the only interviewer who   
   >>liked him and he did perform remarkably well after we'd hired him.   
   >>   
   >>Some op amps are remarkably good - Jim Williams made that point decades ago.   
   >>   
   >>> And how would you demonstrate it?   
   >>   
   >>Run a Fourier transformer on the sine wave generated and look for the   
   >>harmonics?  Build a high Q filter for the frequency you are generating   
   >>and amplify the stuff that gets through it? Check out the Jim Williams   
   >>application notes that talked about the subject.   
   >   
   > How do you propose to acquire the waveform to Fourier analyze?   
   >   
   > Or make a filter with -150 dB distortion?   
   >   
   > All nonsense.   
   >   
   >   
   > John Larkin   
   > Highland Tech Glen Canyon Design Center   
   > Lunatic Fringe Electronics   
      
   If I wanted to build a very low distortion 1k Hz oscillator then I'd build the   
   circuit below.   
   I'd be happy to see 90dB in reality if that could be measured.   
   If better than 90dB can be measured then that's fine but the expense of doing   
   so will likely   
   start to increase exponentially.   
      
   Bill will be along soon to tell us who designed what and how he did this or   
   that but we   
      
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