On Wednesday, April 10, 2002, at 12:25 PM, Sampo Syreeni wrote: > On Wed, 10 Apr 2002, Tim May wrote: >> (A stack of bills, or cards, will have extremely poor radiation >> patterns >> from any but the top or bottom bill, and probably their patterns won't >> be good either.) > > How come? True, if a bill is idealized as being planar, you'll have > trouble on the plane. Spatial diversity will take care of that. > Otherwise, > a common note has plenty of surface to do your thing on. Especially at > higher frequencies, like UHF and beyond.
How come? Because I am assuming the transponders are in the same position on each bill. If you want to posit some "spatial diversity" model, that helps, but not but a huge amount. This sounds too science fictionish to actually deploy (transponders are not the same as letters, and cannot be moved around on a random basis). UHF is hard to launch/receive from a small, planar antenna. UWB is easier to launch from a small (< cm) antenna, but is usually too directional. A stack will interfere, in the sense that planar antennas will couple to each other (radiated signal from A will hit B square on, etc.). As for the proles being too cheap, too gullible to even bother to lightly shield, sounds like evolution in action. Actually, more to the point, it means that the vast infrastructure of "remote bill readers" will, perforce, pick up the proles. True money launderers will use shielding. (Actually, this is all oriented at "walking around money," so the vast infrastructure will never actually get built, as there is no interest in monitoring trivial amounts.) I'm done with this thread, though. --Tim May "They played all kinds of games, kept the House in session all night, and it was a very complicated bill. Maybe a handful of staffers actually read it, but the bill definitely was not available to members before the vote." --Rep. Ron Paul, TX, on how few Congresscritters saw the USA-PATRIOT Bill before voting overwhelmingly to impose a police state
