[Lowfer] 6.78 MHz?

[JD]

>Right, but how about operating under Part 18 (not 15 at all) alone...

Because each part of the rules has its own intended purpose, and the 
purposes stated for Part 18 specifically do not permit such operation.  See 
Sec. 18.107,  Definitions:

"(c) Industrial, scientific, and medical (ISM) equipment. Equipment or 
appliances designed to generate and use locally RF energy for
industrial, scientific, medical, domestic or similar purposes, EXCLUDING 
APPLICATIONS IN THE FIELD OF TELECOMMUNICATION." etc. (emphasis added)

"Scientific" in this case means such things as research into the properties 
of materials, not the sorts of things we do.  For that, there are Parts 5 
and 97, both of which are a lot more flexible in terms of available 
frequencies and permissible equipment.

One cannot build or use just any old equipment under Part 18.  The hardware 
has to be approved and certified under equipment authorization procedures 
specified in Part 2 Subpart J, and a bunch of stuff filed by the 
manufacturer on FCC Form 731.

John