Square Loop Antennas
This week we are learning about and constructing our own square loop antennas. The purposed of this antenna is to use it in parallel with a tuning capacitor to set the resonate frequency to pick up our desired AM radio frequency. For our purposes we will construct the antenna by wrapping wire around a pizza box!
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When constructing our antenna we needed to achieve an inductance of around 215 uH with the trimming capacitor set to 60 pF. This is done to have a resonate frequency around 1400 kHz. To find out the number of time we need to wrap the wire around the pizza box to achieve this we used Joe Carr's formula, shown below.
Figure 1: Joe Carr's Forumula (1)
Figure 2: Resonance Frequency (1)
For the pizza box we used we determined that 16 loops around would give us an inductance close to what we wanted.
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Now the we had constructed the antenna we needed to test how well it worked using the spectrum analyzer and adjust the tuning capacitor to get a resonance frequency around 1230 kHz. Below is a screenshot of our results.
Figure 3: Spectrum Analyzer Results
As you can see we did pretty well getting our resonance frequency spot on to 1230 kHz. In the screenshot we had a gain of -74.6 dBm which is alright, but it went up to around -66 dBm depending on how we held the antenna. The sound from the radio sounded pretty good and I was happy with it. It was decently loud and not too noisy. Might have to listen to some talk radio during my time in isolation.
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In conclusion this lab went pretty well. Wrapping the wire around the antenna was meticulous but we got it done and were happy with the results.
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Citation
1. Stuart M. Wentworth, 2018
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