[Laser] Mystery Modulated Light

[steve kavanagh]

There's not a whole lot to record....it sounds just like a constant frequency tone.  My receiver has significant rolloff above 2 kHz, so the harmonics I hear are probably at lower levels than in the raw signal.  But it might be worth taking a look with an oscilloscope at the receiver output instead of a spectrum analyzer, to see what the waveform is like (duty cycle of pulse, or is it a triangle wave, etc.).

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.  

Maybe there is someone running a beacon with no ID !

73,
Steve VE3SMA