Y'know, I remember electronics kits as a kid
always seemed to include
both an AM transmitter and receiver project...
I'm sure they weren't legal, even back then -
unless there is (or
was) some loophole for devices with really limited range/power.
I think there must be - below some minimum power, pretty much anything
must go in most bands; otherwise, things like spark plugs in car
engines would be illegal because they splatter a little power all
across the RF spectrum. (Not much power, but pretty much clear across
the band.)
However, it may be that, instead, there's a carveout for radiation
which is incidental rather than a primary function, and not
information-carrying, or some such. I know little-to-nothing about the
relevant regulations in any jurisdiction, and they often don't make
logical sense.
/~\ The ASCII der Mouse
\ / Ribbon Campaign
X Against HTML mouse at rodents.montreal.qc.ca
/ \ Email! 7D C8 61 52 5D E7 2D 39 4E F1 31 3E E8 B3 27 4B