Not sure which of these I want to build first.
Pros: Very, very simple.
Cons: It doesn't tune or amplify. As configured above, it's set for VHF.
Pros: Simple, I have the parts already, and advertised as really wide-band (100kHz to 200MHz).
Cons: I doubt it does what the others do---it doesn't tune or amplify.
Talking Electronics's MkI - Pair-of-NPN version.
This one seems somewhere between the above and below designs.
Pros: Amplification, good docs, PCB.
Cons: More complex than the above, but without the tuning of the below, PCB (I'd almost rather just play with my own layout of a Manhattan building technique).
ARRL Antenna Book, Chapter 27
Pros: Circuit design is similar to my SWL-40+, looks like it will be versatile with its tuning and sensitivity changeability.
Cons: Least simple