AM Broadcast Loop Antenna
The Loop wires pick up the radio signal from the radio station and you resonate the loop with the variable capacitor and in doing so the signal is amplified in comparison to a random wire or untuned loop antenna. Then this amplified tuned in signal is passed to your radio with the small 1 or 2 turn loop. doing it this way your radio does not interfere with the tuning of the main loop being they are separate. Also you can tune in stations better if you turn the loop broadside to the station if you know where it is. you can sort of find out by slowly turning the loop till the stations is very week or not there, note what direction the side of the loop is pointing and that's where the station is on one or the other of the broadsides of the loop antenna. so now turn you loop 90 degrees and you have the best position for that station you want.