You're welcome! I'm glad you like it. ^^
Yes, LF/VLF is very interesting and one of the oldest bands. In the beginning of radio, it was considered most useful.
That's why radio amateurs were given shortwave bands originally; everyone at the time thought shortwave would be useless for commcercial/professional use. 😉
Sub marines, by the way, use these low frequencies, too, since these bands work under water.
They are also fascinating to amateurs of astronomy and wheater (sparks, thunder storms).
You can hear the sounds of jupiter, for example, too.
Gratefuly, building an VLF receiver is not much different from building an audio amplifier.
Instead of sound waves, it just receives electro-magnetic waves.
You also don't need SMD parts to make one.
In fact, using big parts (coils, caps, etc) and long wires doesn't harm, sine the wave length is several kilometers in length, anyway.
So you can safely use a wooden board with thumbtacks or any experimental board (Europa card, Veroboard, etc.)
Or just use the soundcard. As an antenna, frame antennas are good.
Some people used big plastic dustbin as a base for their "coil antenna".
If you like to start, have a look at direct-conversation receivers.
They are simple to build and can receive signals that are modulated in AM, SSB or CW (morse code, hellschreiber etc.)
Edit: A sound card works also for reception of SAQ and other VLF signals.
Just make sure it has a sampling rate of 96 or 192KHz. Because of nyquist theorem, the frequency range is half the sampling rate.
(Also note that the soundcard might have filters or a non-linear reception range, so having a larger frequency range is "safer".)
22KHz = 0-11KHz
44KHz = 0-22KHz
48KHz = 0-24KHz
96KHz= 0-48KHz
192KHz = 0-96KHz
Edit: You can also use a band converter. I made one myself, once.
They are very simple to buld if you use a mixer IC. Like the NE612 or SO42P.
Depending on the quartz you install, it can convert signals from say 0-500KHz to 10,000-10,500MHz (if using a 10MHz quartz crystal).
That way, you can use any shortwave radio for VLF reception (around 7MHz is the 40m/41m SW band, so just install a 7 MHz quartz.)
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