At 10:14 PM 2/8/98 -0800, Tim May wrote:
At 9:19 PM -0800 2/8/98, Ryan Lackey wrote:
The physics suggests just the opposite: the RF emissions from laptops are expected to be lower from first principles, and, I have heard, are measurably much lower. (I say "have heard" because I don't have any access to RF measurement equipment...I once spent many hours a day working inside a Faraday cage, but that was many years ago.) ...later... But before going this route, I'd want to see some measurements. Laptops might already be "quiet enough." (Measurements are needed to determine the effectiveness of any proposed RF shielding anyway, so....)
The interference that laptops can cause with avionics is prima facie evidence that laptops are not quiet.
The first principles part is that the deflection yokes in a CRT are the largest radiated component of what got named "van Eck radiation." (I'd just call it RF, but whatever.)
Laptops are missing this component. (It might be interesting to see the radiated RF numbers for various kinds of flat panel displays.)
They are not missing the periodic pixel clocking signals though. ...
With some of these glasses, gargoyle-style, one could completely encase the laptop in a shielded case (like a Zero Haliburton) and then use a palm keypad...
Yes, but cables radiate. Wires are antennae. Used to be a big problem when laptops had wired mice. BTW, in van Eck's original paper, he gives a way to make screen spying a little tougher: pick random raster-lines to draw instead of the usual order. This of course would not be a significant barrier to modern interception. ------ Enrico Fermi used to tune a regular music radio to a cyclotron(?) so he could tell that it was working, I've read. ------------------------------------------------------------ David Honig Orbit Technology honig@otc.net Intaanetto Jigyoubu Lewinsky for President '2012