Aha! OK, well, that name rings a bell! I'll study up on it a bit. Muchas gracias, mein cheese...
When I began to play with this last week, one thing that came back to mind was a really neato article that I remember reading in an ancient issue of CQ (or maybe QST) from somewhere in the early 1960s. (An old ham down the road from me had given me a pile of these when I was a kid - wonderful reading) Anyway, it was an article by a radio engineer named Jerzy Ostermund Tor (spelling approximate). This fellow had developed a two way radio technique using the magnetosphere as the modulated medium, and double loop ferrous antennae for tx and rx. It was called MEMTAC. Have never seen anything on thatin the literature since. Might have been a ruse, dunno; or perhaps died with the inventor before being developed. Still, I wonder if somewhere in Barkhausen noise might lurk something useful. Maybe magnetotactic bacteria could be made to speak up! N --- Keith Nagel <[EMAIL PROTECTED]> wrote: > Hi Nick, > > That'd be called barkhausen noise; a magnetic effect > even your dog can pronounce. The "wooshing" is > caused by the unpinning of domain walls, if > you look carefully at the signal with a scope > you can see the individual avalanches of domain > motion. > > Try it with various samples of transformer iron, I'm > sure you can find certain samples that will show > the effect very strongly. Your "bahhh" instinct is > correct, the effect was discovered in 1919. > Google on that keyword for more information, and > consult your Bozorth for details. You do > have a copy of Bozorth, huh? Well buy a used one, > for bogs sake! Indispensible ref for things > magnetic. > > K. > > > -----Original Message----- > From: Nick Reiter [mailto:[EMAIL PROTECTED] > Sent: Friday, November 25, 2005 4:28 PM > To: [email protected] > Subject: Radio Free GMR > > > ...or what is the sound of one electron flipping? > > Rather than go into a long winded preface describing > the circumstances of a curious little effect I have > been listening to lately, let me toss this out to > the > scholars of electrons. > > Is anyone aware of a source of white noise in > electronic circuits that is related to either > magnetic > domain or electron spin polarization? (Or > de-polarization?) I've been playing with non- or > micro-inductive coils made from ferromagnetic > materials (nickel wire mainly) and I've found a neat > effect that manifests as a burst of strong hissy > white > noise "whooshing" when a large magnet is moved by > hand > toward the coil. To get a second whoosh , I have to > pull the magnet away, flip it over to the opposite > polarity, and then push it toward the coil again. > As > if the burst of white noise comes from domains being > de-polarized and re-polarized... hysteresis noise? > Replicating the actions with an identical coil made > from copper wire produces no such effect at all. > > Just starting to play wit' dis' one, so my reports > may > be sporadic here. My "bahhhh" nature says that this > must be something well known, but I've never run > into > it before. > > Still, I've been thinking along the lines of > spin-spin > communication, and more pragmatically, spin > polarized > radio. I've been trying to bone up on GMR and spin > valve materials technology. Maybe there is some > connection here? > > NR > > > > __________________________________ > Yahoo! Music Unlimited > Access over 1 million songs. Try it free. > http://music.yahoo.com/unlimited/ > > > __________________________________ Yahoo! Mail - PC Magazine Editors' Choice 2005 http://mail.yahoo.com
