When you think of an antenna, you probably imagine a large conductive metal sticking straight up into the air. A loop antenna is basically an antenna that comes back around instead of sticking straight up into the air.
It doesn’t matter what shape the loop antenna is. It could be a round loop antenna, a square loop antenna or even a piece of metal shaped like a star. What makes a loop antenna what it is is that on both ends of the conductive metal are connected to the same capacitor. Adjusting the antennas capacitance will change the frequency.
There are two types of loop antennas: a small loop antenna and a large loop antenna. A loop antenna is a small loop antenna when the length of the loop stretched out is less than the wavelength divided by 10.
Small loop antennas are primarily used as receiver antennas because they have a very high reactant and the impedance is hard to match with the transmitter.
Large loop antennas usually have a circumference close to one wavelength of it’s operating frequency.
Why are loop antennas used?
Loop antennas receive radio signals more efficiently than other kinds of antennas. They are generally smaller so they are easier to carry around and they use less electricity.
Loop antennas can be used in direction finding equipment. This is important for planes or ships that need to use directional equipment as a navigational aid. Loop antennas are capable of determining which direction the frequency is coming from.