[time-nuts] Inductor core material aging (was: Rohde & Schwarz XSD 2.5 MHz crystal gone bad?)

[Graham / KE9H]

The core of the inductors are commonly powdered iron (of various alloys),
held together with a plastic binder.
The early plastics shrank and changed shape with time, changing the
inductance over decades.
Later binders are much more stable.
Not much you can do about it, other than change the inductors.

--- Graham

==

On Mon, Nov 21, 2016 at 10:14 AM, Bob Camp <kb8tq at n1k.org> wrote:

> Hi
>
> > On Nov 21, 2016, at 9:23 AM, Attila Kinali <attila at kinali.ch> wrote:
> >
> > Hoi Bob,
> >
> > On Sun, 20 Nov 2016 22:21:29 -0500
> > Bob Camp <kb8tq at n1k.org> wrote:
> >
> >> 50 year old inductors may have been made with core materials
> >> that aged more than just a little bit. I have empirical data on this :)
> >
> > Do you have that data available somewhere? I would be very much
> > interested in it.
> >
>
> We had a few thousand oscillators that had to be replaced due to coil
> issues
> in the 1970’s. We were not the only ones with the problem. Other outfits
> had very
> similar experiences. Eventually the coil guys took a look at the materials
> and
> “changed something”. After that the coils did not have as much aging when
> run at 100C forever and ever.
>
> Bob
>
> >                       Attila Kinali
> >
> > --
> > It is upon moral qualities that a society is ultimately founded. All
> > the prosperity and technological sophistication in the world is of no
> > use without that foundation.
> >                 -- Miss Matheson, The Diamond Age, Neil Stephenson
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