Re: Tecsun AN-200 = Sutekus
Yes the tuning on the loop needs to be very precise. A touch either way and you loose the peak. It is also pretty critical where you place the radio relative to the loop. With some of my small radios I actually put the radio inside of the loop. Perpendicular sitting right at the bottom. But playing with the distance and orientation of the radio relative to the antenna will make a huge difference. I also bought a Lazy Susan (rotating disk/platter on bearings) to be able to aim the radio and antenna at the same time. Remember the antenna is directional along the plane of the loop. So the edge (the direction the wire is wound) is what needs to be pointed at the signal and the radio.
From Wikipedia "The radiation pattern of a loop antenna peaks at right angles to the plane of the loop".
I have several of these small loops. When used correctly, and depending on conditions they can make the difference between a copy and none. They are also good for nulling noise and adjacent channels. I have a couple connected to fixed radios (AM/FM tuner connected to a surround receiver) just to null noise even if just for some local stations. They can definitely be very useful when used correctly.
Play with it some more, you may be pleasantly surprised.