From: bill.sloman@ieee.org   
      
   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.   
      
   --   
   Bill Sloman, Sydney   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)