From: jl@glen--canyon.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:
0emofm$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
--- SoupGate-Win32 v1.05
* Origin: you cannot sedate... all the things you hate (1:229/2)
|
