Date: Thu, 11 Mar 1999 16:52:41 -0500 (EST)

Author: Steve Wonnell

Subject: RE: More non-Barkhausen effects


I tried putting the coil, but not the whole apparatus, inside a faraday
cage with 1/4" grid (good enough for the radio in a cage demo for the
lowest radio frequencies). No change...I think the background noise is
partly due the amplifier. In fact, there seems to be a small potential
difference at the back of the amplifier...perhaps driving a small current
through the coil...adding the yoke changes the load and hence the current?

I sure wish I had a Faraday caged room. Steve, are your lights, computer,
and other stuff outside of your cage?

Steve W.

On Thu, 11 Mar 1999, Steve Anderson wrote:

> Date: Thu, 11 Mar 1999 13:41:02 -0700
> From: Steve Anderson
> To: tap-l
> Subject: RE: More non-Barkhausen effects
> Reply to: RE: More non-Barkhausen effects
> > In other words, it's sort of as
> >if there's some sort of very tiny induced current in the loop...from
> >electromagnetic fields maybe? and the insertion of the yoke increases the
> >induction.
> >
> This sounds like it to me. I have a Faraday caged room, but that is the
> only place where you can get away from the ubiquitous 60 Hz humm. In a
> doubly amplified pick up coil this doesn't sound surprising. Maybe its
> an ac material permeability checker? When I measured the magnetic
> fields from monitors it had to be done in the shielded room or the
> normal power line ac fields were 100 - 1000 times more than those
> fields.
> Steve Anderson, ET III "B here always"
> Physics & Astronomy Dept.
> Sonoma State University
> 707-664-2330 fax 664-3012

Steven K. Wonnell
Physics and Astronomy Department E-Mail:
Johns Hopkins University Phone: (410) 516-4696
3400 N. Charles Street Fax: (410) 516-7239
Baltimore, MD 21218-2686 Office: 403 Bloomberg (x0544)