I'm only going to use it for basic noise detection around the house and neghborhood (smart meters, bad transformers, exc), so I am going for a very basic setup. I just need it to give a rough direction and strength, I don't need the frequency spectrum. This is more of recycling junk into a neat gadget, I love working with old tech, but I do want it to be fully stand alone. I call it an RDF but more of a directional EMI detector (IE wideband noise).
As for the antenna, I want to use multiple antennas instead of a mechanical method so I don't have to use a servo that could possibly introduce its own noise. Bulk does not matter, as long as it can be held, this won't be battery operated so it won't be able to move far from a plug. I'll ask some of the guys in my antique electronics club what type of directional antennas they could sell to me (If they have a rotating one I'll use that and modify the system accordingly).