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The goals of this lab are to design and construct a square loop antenna and then tune it for optimum reception. A square loop antenna is essentially a large square inductor with N turns, side length A, and depth B. A wooden frame is often used to make them. The sensitivity of the antenna increases with the area, so a larger area antenna is able to recieve stronger signals. The antenna gain is typical small, but can be increased by placing a capacitor in parallel to create a resonance structure. A trimmer capacitor, which can be tuned within a range of capacitances, works well as a frequency tuner for the AM radio.
My team's square loop antenna was designed around the constraints of a large pizza box and the trimming capacitor that came with our lab kit. To find the inductance value for our antenna, we used Joe Carr's inductance formula.
After calculating an inductance value that could pick up frequencies from 1230kHz through 1520kHZ, we used the closest value that could be achieved by our pizza box constraints.
Once the antenna was built, we used my radio circuit to test the out the antenna. It consists of the CS/CE RF amplifier, a biased diode detector, and a CE/AB push pull audio amplifier. With te square loop antenna, the radio was able to produce an easily audible sound when the radio picked up a frequency.