From: jrwalliker@gmail.com   
      
   On 12/11/2025 15:37, john larkin wrote:   
   > On Tue, 11 Nov 2025 11:10:46 -0500, "Edward Rawde"   
   >  wrote:   
   >   
   >> "john larkin"  wrote in message news:l5l   
   hkp3ssdvsnumf19sf6t0jrmtjop0im@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 ne   
   s: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   
   >>   
      
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