[RFI] Mystery noise

[k1ttt.dave at gmail.com]

>   This thing shows up periodically - happily not often.  The 
>periodicity makes me think switching power supply, but aren't they 
>normally discrete , sometimes noisy, sometimes drifty but fairly narrow
>
>critters? This has a substantial 120-Hz component, but why every 19 
>KHz?

Well, when you mix several signals non-linearly you get all the +/- combinations of the fundamentals and harmonics.  So you've got 60hz line frequency harmonics giving you the 120hz component plus the switcher's 19khz switching rate and all its harmonics adding and subtracting from light to -light along the real and imaginary axis!


David Robbins K1TTT
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