Re: Reflected Signal Problem

[Joyce Poon <poonj@ecf.utoronto.ca>]

>From what I have been reading on the webpage, there are only certain
frequencies you can modulate your signal to for the sensors to work
(modulate = "key a certain frequency" in Tim language).  IR sensors come
in kits (an IR emitter + a detector&chip thing).  I figure there aren't
that many commercially available IR sensors so most groups may be in fact
using detectors of the same make (or of similar make).  Hence, the signal
frequencies of all the groups may actually be the same. (eg the Sharp
model -- which seems to be very popular and widely available-- runs at
40MHz.)  That's why I am slightly concerned about the reflected signal
problem.

Secondly, I think "interference" does not refer to intentional 
interference from other groups, but rather from electrical noise/light
noise from the signal & also the potential EM field generated by the
motors.  The former problem will be solved by building good filters and
boosting the good part of the signal.  The latter can be solved by 
shielding the motors.  I don't think we have to worry about other groups
deliberately interfering with beacon signals.  Apparently, this is very
hard to accomplish and I heard Malone said (to another group) that no
groups had ever succeeded in interfering with beacon signals.

Joyce :)