Lab 6: Square Loop Antennas
Lab 6 involved writing a MATLAB script to find an antenna configuration, building the antenna, and integrating all the parts of the radio.
The MATLAB code I wrote takes the coil edge length, coil depth, and number of turns and calculates the inductance of the coil using the formula provided in the lab manual. It then calculates the capacitance needed to receive three of the AM radio stations available in Auburn. It also calculates the difference in capacitance needed for the highest and lowest frequency station. This allowed me to shoot for a capacitance in the middle of the trimmer capacitor's range while also ensuring that the higher and lower stations would still be tunable.
My pizza box was 12" x 12", so using the script I decided on a 10-turn antenna,which would let me use a 100pF capacitor to push the capacitance high enough for our trimmer capacitor to tune all three stations.
Figure 1: MATLAB script with antenna parameters and output data
Building the antenna was straightforward. I marked out locations for slits in the corners of the box, cut them with a pocket knife, and wrapped enameled wire around the box. Figure 2 shows one corner of the box after the coil was wrapped.
Figure 2: Pizza box antenna
The antenna was connected it to the radio along with the trimmer capacitor and a 100pF capacitor in parallel. I was briefly able to receive a station faintly, but it faded nearly immediately. I never had success receiving a radio station with my radio, but I connected my antenna to another student's radio and was able to easily tune to a station, confirming that my antenna was functional. A video of this successful reception is shown below.
Figure 3: My antenna receiving a radio station