From: bill.sloman@ieee.org   
      
   On 11/11/2025 8:06 pm, John R Walliker wrote:   
   > On 11/11/2025 07:38, 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:   
      
      
      
   >>> 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.   
   >>   
   >> 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   
   >   
   > Teflon has phase changes at 19 and 30 deg C which make it very   
   > hard to get stable performance over temperature.  This also affects   
   > coaxial cables in high precision applications.   
      
   A reference low distortion sine wave generator isn't going to be used in   
   hostile environments.   
      
   Nobody makes much fuss about the frequency stability of these low   
   distortion sine wave generators - I have worked out a scheme to add in a   
   small controllable quadrature component to let you stabilise the   
   frequency as well as the amplitude but it never generated any interest.   
   The phase change in the Teflon film probably wouldn't be a problem in   
   this application. It's not as if it is going to generate harmonics.   
      
   --   
   Bill Sloman, Sydney   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)