Earlier this year I obtained a vlf converter from Datong trough eBay. The total cost including shipping was about 12 euro. A real bargain. I saw the same converter a few weeks later again on eBay, this time it was won by a Frenchman for more than 60 euro. The Datong converter converts the vlf band to 28 MHz, so 28.000 MHz is actually 0.000 MHz.
28.136 MHz is the 136 kHz amateur band. And so on.
You can also convert the medium wave bands too but at reduces sensitivity according to the manual.
I attached a kind of loop antenna to the input wich hung in the bedroom (XYL not happy) and started listening to all kind of stations. I heard a NDB beacon from North-France and many others. DHO38 on 23,4 KHz was loud and clear. Many other stations were heard.
The transmission of the VLF transmitter at Grimeton was planned fot july first. On a sunday. My XYL had to work so I took the kids and all my gear to my parents home. This time the videocamera was packed too.
The antenne I made that day was a bit too large for the converter, the manual says that it has a lot of gain, a small whip antenna should be enough. The 14 by 2 meter loop produced strong broadcast signals everywhere. Found a potentiometer and wired it in the coax line to reduce the signal. Much better.
The result of this setup can be heared and seen on this short video I made and posted on YouTube :