From: legg@nospam.magma.ca   
      
   On Mon, 26 Jan 2026 17:56:10 +1100, Bill Sloman    
   wrote:   
      
   >On 26/01/2026 2:44 pm, legg wrote:   
   >> On Sun, 25 Jan 2026 08:08:48 -0800, john larkin    
   >> wrote:   
   >>   
   >>> On Sun, 25 Jan 2026 08:51:24 -0500, legg  wrote:   
   >>>   
   >>>> On Sat, 24 Jan 2026 19:25:35 +0000, liz@poppyrecords.invalid.invalid   
   >>>> (Liz Tuddenham) wrote:   
   >>>>   
   >>    
   >>>> In applications where power levels are important, pot core orientation   
   >>>> will affect 'N' in the flux density concentration, and produce early   
   >>>> saturation at the location where minimum x-sectional area occurs.   
   >>>>   
   >>>> RL   
   >>>   
   >>> That should have a small effect on my pulser. Ill try it.   
   >>>   
   >>> I got a 2% change in inductance when I rotated the core halves.   
   >>>   
   >>>   
   >>> John Larkin   
   >>> Highland Tech Glen Canyon Design Center   
   >>> Lunatic Fringe Electronics   
   >>   
   >> 2% FREE x-sectional area, and an indication that the previous   
   >> misalignment doesn't dominate minimum value.   
   >>   
   >> Mind you, you can get a similar change just by forcing out   
   >> the fluff and detritus present at the contacting surfaces.   
   >> That might be what you're actually seeing, even if the core   
   >> is gapped.   
   >>   
   >> In pot cores, minimum x-section usually occurs where the centre   
   >> core meets the top and bottom plates. In parts shapes designed   
   >> for power applications, this is usually corrected.   
   >>   
   >> This core rotation can be used as a tolerance trim, where   
   >> needed, but anything like that before impregnation is probably   
   >> just biting fart bubbles.   
   >   
   >There is a way of doing trolerance trims on some gapped pot cores.   
   >   
   >The manufactures put cylindrical hole down through the centre of the   
   >core, and sell an adjustor which plugs  into the hole. There a ferrite   
   >slug in the adjustor which you can screw up and down to fully or   
   >completely bridge the the gap between two core halves.   
   >   
   >I've used them, and they provide enough adjustment to let you trim out   
   >the residual tolerance on the inductance of a gapped core which can get   
   >up to perhaps +/-5%, and a bit more.   
   >   
   >The one time when I designed one in to get a precise 15MHz source for TV   
   >style video, one of my colleague engineers copied the design for a much   
   >higher volume project, he left out the adjustor - we were also using a   
   >varactor diode to accomodate the frequency difference between production   
   >TV displays and he figured that that - one its own - could cope with   
   >both sources of variation. Varactors are very non-linear, and I was   
   >worried about getting out of the region where they were linear enough.   
   >   
   >Jerry was a very good engineer - if not all that self-confident - and   
   >I'd been warned off expressing any doubts about his designs, because   
   >he'd take my doubts much too seriously.   
      
   Pot cores were developed for tube-amplitude cctry. I expect that   
   adjustible varieties had added cost. How did it compare in cost to   
    the addition of a varactor?   
      
   For semiconductors, you'd get away with slug tuned 'can' - still   
   candidate for a varactor.   
      
   Lots of headaches with pot cores - mounting, termination etc. The   
   smaller parts actually increased in price . . . .   
      
   RL   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)