Square Loop Antenna

The purpose of this lab was to design and construct a square loop antenna and to tune the antenna for optimum reception. This square loop antenna was to be constructed using a pizza box and magnet wire.

We were first instructed to calculate the inductance required for 1400 kHz using a 60 pF capacitor. We measured the pizza box and determined A = 16.375 inches and B = 2.125 inches. First, I plugged f = 1400 kHz and C = 60 pF into the equation below to determine L = 0.000215 H.

Next, I plugged L = 0.000215 H, A = 16.375 inches and B = 2.125 inches into the equation below and determined the N = 15.68 turns. We rounded this up to 16.

Finally, I plugged f = 1230 kHz and L = 0.000215 H into the equation below to determine C = 51 pF. 51 pF is the maximum capacitance that is needed.

Next, we used the HP 8920A RF Communication Test Set in the back of the room to adjust the trimming capacitor. We saw a peak at -68 dB and we determined that this was good.

Finally, it was time to build the antenna as shown in Figure 1. The antenna and the trimming capacitor were connected to the circuit in place of the function generator. When we tested the radio, no noise came out of the speaker. We were expecting static, then the antenna would be moved around to pick up voices. We decided that we would test the circuit with the antenna outside but this did not work either. We are working to determine a solution.

Figure 1: Finished Antenna Connected to the Circuit