[Laser] Mystery Modulated Light

[KD7JYK DM09]

"I agree with Stuart that most of the LED drivers I have seen data sheets
for operate above 30 kHz. I did see one that was FM-ed at a 1 kHz rate to
minimize EMC spectral density problems."

That's the driver.  You are picking up modulated light.  It may run off 60
Hz AC, but you don't see that.  Maybe half or full wave rectified DC from a
wall wart powering a switching mode power supply operating from some 30 KHz
to 200 some-odd KHz, you don't see that either.  Maybe just four AA cells in
a box powering an LED closet light...  No modulation there.  By the time the 
power is converted and sent to the LED, which you can see (hear), it's at 1 
KHz, the power source/drive could be most anyhting operating at most any 
frequency.  Take the "dancing tail lights" on cars.  The power supply is 
around 14 Volts DC,
God only knows what happens to that DC voltage before it gets to the LEDs in
the tail lights, by the time you see it, it's perhaps as high as a few 10's
of Hz.

Kurt