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I’m not sure if you’re interested, but the machine transmitter SAQ in Grimeton, Sweden, will send out its Christmas greetings soon (on Christmas Eve).
In case you don’t know what I’m talking about, here’s a short and simplified explanation.:
SAQ is a historical machine transmitter, using a generator to send messages using morse code (also known as CW, Continous Wave).
Every time around Christmas, it sends out best wishes on 17.2 KHz (or 17,2 KC/s for the british people).
As you notice, this frequency is very low and belongs to the VLF bands (very low frequency), which is even below longwave.
In fact, it is somewhat low that is within the frequency range that is normally used for audio (AF, audio frequency).
Now, you may ask why I’m telling you this..
Well, most sound cards with a 44KHz sampling rate can actually receive upto 22KHz (see nyquist theorem).
Which means, it is actually possible to attach an antenna to the line-in jack instead of an audio source.
This way, you can hear this historical machine without any special hardware! Cool, isn’t it ?
I didn’t find the right solution from the Internet.