Cell-Phone Tracking - Big Brother is Watching

[Aggie]

Don't encourage me, Scrib. 

_{ok, ok, I'll put the NaOH away.....}

[Bob in a quantum-state-of-faith]

_{If one wanted to take revenge on a despised foe, hiding a rare-earth magnet in their wallet would do the trick nicely.}

MythBusters had an episode where they tried using magnets to wipe credit cards.

The results?  No go.

A fixed-field magnet (including all the rare-earth ones) is simply not going to have much effect on a magnetic stripe.

They tried several different varieties, leaving them overnight, etc.  Even some of Jamie's really honkin' huge rare-earth's the size and shape of hockey-pucks.  (and are strong enough to actually remove fingers, if caught underneath).  No effect-- their card reader was easily able to read the magnetic stripe after exposure to fixed-field magnets.

The key, is a moving-field magnet.   To get a fixed-field magnet to wipe a magnetic strip, you have to have either the magnetic strip or the magnet or both, moving quickly, and over a long period of time-- preferably random movements.  But even then, it does not always work reliably.

If reliable wiping is your goal:  switch to alternating-field magnets, or electromagnets powered by an AC current.  DC electromagnets are the same as fixed-field, permanent magnets, so they do not work.

But, those alternating-field AC-powered electromagnets?  They will wipe out *any* magnetic information from inches away....

---------------

How does he know all this, some may ask?

Years ago, back in the 80's, when I was deeply into a PC-based business, 5 1/4" floppy discs cost roughly $5 each, in bulk.  Much higher, in small lots.  So, I developed a regimen of recycling these into re-use.  I found the best method, was to blank-them out with AC-driven magnets, then re-format.  This ensured a nice clean "base" for the new data.  Simply reformatting them did not always work well, I discovered through experience.

And yes, I tried any number of fixed-field magnets, before settling on the field-coil salvaged from an AC-induction motor-- but it was pretty weak, and had to be physically passed over both sides of the disk, to ensure complete blankage.

From whence comes the inches away reference?  Telephones.

Back in those days (no cell phones, no electronic phones of any sort-- ancient Bell-inspired electromechanical phones only) all telephones had a lovely, and loud, bell-ringer.  This thing consisted of a pair of actual metal bells (like on a bicycle), with a metal clapper between them.  The clapper was driven by-- yep, an AC-powered electromagnet.  And it was incredibly inefficient-- most of the energy leaked out into the environment-- poor design.   The AC current is what caused the clapper to flop back and forth, striking each bell alternately.

Anywho, if you placed a 5 1/4" disk next to, underneath or near to one of these ancient testaments to barely good enough engineering, any time the phone rang, it would likely as not, wipe out your disk.

From inches away, even.   

Learned that the hard way. 

[Aggie]

I stand corrected - Myth busted!


And I do remember taking apart one of those telephones when young-ish.  I grew up with rotary-dial electromechanical phones.  I suppose inefficiency wasn't a big issue, because they were powered strictly off the telephone line, with nary an electrical outlet required.

You did clarify one point I'd wondered about - if rare-earth magnets can wipe a magnetic stripe / disc / tape from a short distance away, floppy discs would not have likely played nice next to hard drives in those old PCs without shielding (which they may have had, I don't have a clue there).

[Sibling DavidH]

I've got a videotape bulk eraser; the idea was it was supposed to restore the quality to much-used VHS tapes.  I couldn't be sure if it helped, but it  erases a floppy instantly.  I once did a bulk job for the charity: several dozen floppies wiped in a few minutes. (Of course, you have to reformat the floppies if you want to re-use them.)
Incidentally, when I've tipped out my junkbox of small screws, etc all over the table it'll pick all but the brass ones up and drop them back in the box in 2 or 3 goes.

[Swatopluk]

You did clarify one point I'd wondered about - if rare-earth magnets can wipe a magnetic stripe / disc / tape from a short distance away, floppy discs would not have likely played nice next to hard drives in those old PCs without shielding (which they may have had, I don't have a clue there).

Not to forget that the hard drives themselves are magnetic storage discs. I wondered how they could work with such a strong magnet in them.

[Pachyderm]

Just had an entertaining thought. If they can track your phone, what would make of a plot of my movements?

"Subject drove across the country, stopped for some reason (coffee), then carried on. Subject then left his vehicle (trace indicates subject no longer travelling at 70 mph), and wandered around a series of fields, apparently in a random manner. No link has been established between subject and registered owner of land. Subject drove to an area subsequently identified as woods, and wandered around, apparently in a random manner. No link has been established between subject and registered owner of land (City Council). Subject returned to vehicle, and returned to Belfast. We have no logical explanation for this behaviour, so are placing him on a watch list."

[Aggie]

There's going to be no need to be sneaky about it soon, thanks to apps like FourSquare and twittering - people are broadcasting their own whereabouts voluntarily.

http://technology.canoe.ca/2010/02/25/13019026-ap.html


LOL @ Patchy - I pack a SPOT (satellite personal tracker) unit when afield and alone.  Triangulating off the nearest towers doesn't work so well in the Canadian wilderness, 'cause there's rarely three in range.

[Sibling Zono (anon1mat0)]

Pachy, it's easier to put a harness on a cat and place the phone in it, the cat will do it's daily errands and eventually come back home.

Then you ask the feds/MI5/[insert domestic intelligence agency here] to finally solve the mystery of where does your cat go when (s)he leaves the house.

[Bob in a quantum-state-of-faith]

You did clarify one point I'd wondered about - if rare-earth magnets can wipe a magnetic stripe / disc / tape from a short distance away, floppy discs would not have likely played nice next to hard drives in those old PCs without shielding (which they may have had, I don't have a clue there).

Not to forget that the hard drives themselves are magnetic storage discs. I wondered how they could work with such a strong magnet in them.

Most of the magnetic energy is routed by iron straps around the magnets-- if you look at the construction, they are wrapped top and bottom with steel (usually plated).  Magnetic fields appear to "prefer" staying within magnetic elements, as opposed to within the air.

So those drives do contain two rare-earth magnets, within millimeters of the magnetic disk.  But the steel strapping keeps the magnetic fields in check.

But think on this:

A floppy disc, be it 5 1/4 or a 3 1/2 is basically a piece of Mylar plastic with a thin coating of rust on each side-- yet, you can have within fractions of a  millimeter-- two separate magnetic tracks on either side of that thin piece of plastic.

It's all in the intensity.