[Lowfer] 9 Khz. & Below in USA

[Charlie , W5COV]

I know that there are some people in the USA , that are experimenting on 
these frequencies with transmitting equipment .

Can someone tell me what is legally required to experiment on these 
frequencies ? At what frequency does the FCC begin to regulate the lowest 
frequency that requires their permission of some sort to transmit on ?

I would also be interested in exchanging information and ideas with anyone 
currently involved with such projects in this frequency range .

This is a completely new area of interest to me , so I know absolutely 
nothing about it .

The lowest frequency that I am actively involved in is monitoring 24 KHz. 
for use with a SID detector , which is in the construction stage .

Any information would be greatly appreciated .

73 ,

Charlie , W5COV