What is a Magnetic Loop?
A Magnetic loop or STL (small transmitting loop) is a large coil with a capacitor added to bring the system to resonance. It is unlike a large resonant loop (more common) in that the loop size is smaller than 1/4 wavelength and does not resonate on its own. The loop is brought to resonance by attaching a capacitor to the two open ends of the loop. The loop is tuned by a changing the value of the capacitor. An increase in capacitance will bring the resonance of the loop lower in frequency, a decrease in capacitance will make the loop resonate higher. An excellent resource for more in depth information is the ARRL Antenna Book, section 5 (there is a lot of good info, but don’t believe everything you read!).
