In message , Steve
Sands writes
I need to create an AM modulated carrier of 25 Khz that is highly
focused in beam width. I am aware of part 15 and will not be using
this for any other reason than for research. I need a range of 50
feet. Receiver will be a tuned resonant tank with about 90 db of gain
post detection. I would like to be able to "focus" this beam but being
in optics I have no idea of how one might control the dispersion of a
carrier like this. In other words in my field I can collimate or focus
a light beam but dealing with this wavelength I have not a clue!

Thank You in advance for your input

Same principles, just scale up!

Mike

PS. I don't think you can do it. At 50 ft you will still be inside the
near-field for both electric and magnetic components of the RF. The wave
hasn't yet assembled itself into an electromagnetic wave.
--
M.J.Powell