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You should read the VLF link carefully to understand the ambiguousity involved with your question. VLF radio is wireless transmission using antenna. There's no lower limit except that's set by what you regard as an acceptable antenna size.
It is probably the so called Earthquake Waves that can be heard on 1-100Hz or so.
Every radio frequency uses some kind of antenna, either it is a long wire or a loop or whatever.
You can receive so low frequency waves using an audio amplifier
And a simple way to transmit is also an audio amplifier, or spinning an AC motor at the freqiency you want, eg 50Hz Just a dirty and quick note..
Low frequency wireless electromagnetic waves are mainly used by submarines, if we limit the question to manmade signals with intension to communicate. A common frequency band is 60-70 Hz.
Waves in form of modulated air or water pressure can also be used as a kind of wireless communication but can not be transferred over electromagnetic antennas.
Other types of slow electromagnetic waves, only indirectly used for communication:
As North Pole periodically switches polarity does it cause real low frequency electromagnetic waves.
Big bang is maybe the slowest wave of them all, if it is a continuously repeating wave. We have however not got it confirmed yet.
Some experts believe that the switching will go fast, others not and some says it will not happen at all (this week).
It starts with increased instability of magnetic pole relative earth axis. The last years have magnetic north pole moved more then 50 km each year and speed seems to have quick accelerated since 1999, so it maybe already have started. It can as well also be a natural variation in north pole behavior.
When the switching occur can it be a few days with high instability. During these days is it better to remain indoor due to high levels of particle radiation. Some experts says that instability will remain during 5000 years but it will maybe not occur within 1000000 years yet.
"When" is probably similar problem as to predict when a earthquake will happen.
One of the experts will afterward say that he was the only one with correct crystal ball.
Long time to stay indoor anyway.
I am pretty sure the switch will happen. There is a big rift in the middle of the pacific ocean, and they can run a magnetometer over the area and see a complete change in the magnetic orientation of the cooled magma in distinct bands (time) over the millenia. Also, on only good navigation map, you will notice that the magnetic declination is always changing with time, albeit slowly. They tell you the magnetic declination on the date the map was published, so you can recalibrate it in future years.
I just wonder if it takes time to swap poles, and if the magnetic fields at the poles are the only thing keeping us from being fried by nasty high energy space particles, what happens for the year(s) when it is actually swapping poles midway? Do we still get the magnetic field protection, or does our magnetic shield die out for a while when the switch happens?