[LAU] 'morse code' picked up by the speakers

Chris Caudle chris at chriscaudle.org
Tue Jun 13 18:40:29 UTC 2017

On Tue, June 13, 2017 12:04 pm, jonetsu wrote:
> Yes, that's the case.  Just to add to this a tiny bit, cell phone
> waves are way up there in the frequencies, so that cannot make such a
> low pulsating interference. Not sure, but it seems that the cell phone
> waves are modulated in the (very) low frequency range

Yes, correct.  GSM is especially bad in that regard, there is a time
period when the signal must either be modulated very heavily, or is going
between on and off or almost off.  Quite annoying, but has the good
property that interference is usually very noticeable, less problem of
wondering if there is or is not a problem.

> modulation is what's picked up by the (magnet of the) speakers.

Unlikely to be the magnet.  The speaker model you mentioned previously is
an active speaker, with an amplifier built in.  The first stage of the
amplifier is likely sensitive to interference.  The junction of a
transistor is the same semiconductor structure as a diode, which can be
used to demodulate AM radio. In essence the amplifier built in to the
speakers was designed without proper protection against radio frequency

Chris Caudle

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