Through experimenting, I discovered that my Terk AM Advantage works best at a 45* angle from a radio’s internal ferrite bar antenna. Locate the radio’s (internal) ferrite bar antenna at an approximately 45* angle with the 2″ Terk AM Advantage loop.
Antenna direction
Place the, approximately, 2 inch side of the Terk AM Advantage loop facing the AM broadcast antenna source i.e. the narrow 2″ side should be perpendicular to the direction of the desired station .
small radio placement
I, also, discovered that the best placement (relative to a Terk AM antenna) for pocket AM radios is, actually, INSIDE the Terk AM antenna loop i.e. sit the pocket radio inside the Terk AM antenna loop! This results in a bit stronger signal; for example, my Degen DE1105, which has a 10 bar signal strength meter, gains an additional 2 bars by standing the DE1105 inside the Terk AM Advantage antenna (compared to its signal strength in the otherwise best location outside the Terk AM Advantage loop).
Though I don’t have the similar Select-A-Tenna or Degen TG-39, I have no doubt that due to the magnetic coupling they would work similarly to a Terk AM Advantage.