Radio Man wrote:

Where in the U.S. can i purchase powdered ferrite in
order to make very large ferrite rod antennas?

How big?

I'm not 100% sure but I think you might be able to bundle together commercially
available rods and also glue them end to end to make a large rod.

I'm sure the powder is available, but of course you'd need to have some kind of
press to form the rod, and a kiln to fire it.

dxAce
Michigan
USA