Cell Phone Detection

For P150, "How Things Work", Harold Ogren asked me to construct a cell phone detector.

A google search found "The Amazing All-Band Receiver" on Charles Wenzel's www.techlib.com which was the starting point for my design. We wanted a speaker as well as headphones, so an OP-07 op amp was used to provide enough gain. Headphones, a more powerful amplifier, or a computer's audio input can also be plugged into the phone jack. It will pick up car remotes, computer WiFi, microwave ovens, strong radio stations, etc, as well as cell phones. Different diameter loops or a telescoping whip can plug into the BNC antenna input.

Here is the schematic (click on it for pdf version):

We also wanted a way to make relative measurements of the RF field strength, so a simple RF detector was constructed in a Pomona box that plugs into a digital voltmeter. A nearby cell phone gives a reading of ~1.5 volts.

Here is the schematic (click on it for pdf version):

Here are some pictures:

Waveform from a wireless remote control.

Paul Smith
Indiana University Physics
email: ptsmith@indiana.edu

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