Electronic Entomology

Radio Bug

Revisiting Experiments from 6/2021 in New Haven, CT

This post is a documentation of a brief experiment on a bug with a new energy harvesting organ - radio antenna. This experiment is based on “FM snake” device developped by Eric Brasseur and adapted to be integrated to a bug.

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In the article Eric demonstrates harvesting energy from FM radio tower ranging from 88 ~ 100 MHz located 1 kilometer away. It is surprising how strong the signal is. It does make sense considering how far it is trying to transmit but it is something I totally forget when I am close to the towers. I kind of get the fear of radio waves and aluminum and magnetic shedding for your home. Not that I feel the need to do these things but remembering how strong these electrical magnetic pulses that radiates for miles penetrating through objects, I can empathies with that fear.

It is such an available forces that is present all the time. It is interesting this technique is not popularized as much as I thought. I presume it does not produce anywhere enough current and voltage for any common electronic devices we use today. Though it did produce enough for lighting an LED light - at least 1.2V ish and only need few micro-amp.

Energy Harvesting Organ

Here is the schematic of this organ below. Adaptation of Dipole antenna design form Eric’s website. There are pair of shotkey diodes and insulated wire. I have replaced LED (load) to positive and negative for my bug.

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Referenced from http://www.ericbrasseur.org/electrosmog_snake.html

Dipole antenna length can be calculated with formula provided by this article here

length (m) = 150 * A / f

A = variable from the gage of wire typically 0.98
f = frequency

According to the article detection diodes should be located at the 1/4 length of the entire length. The total length is adjusted to the frequency of the radio tower near by.

Hunt for the tower

Trough the website fmscan.org I found the radio tower located near New Haven CT in WestRock. I have seen this tower when I hiked around that area before.

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The tower is transmitting 94.3 mhz so

150 * 0.98 / 94.3 = 1.55m

I did make the antenna to be extra 10 cm long to start with just in case and I can cut to adjust to the needs. When I arrived to the location, length I brought was not producing any sounds so I trimmed a few round and at 158cm, it started to make sounds! It seems like some times it made more sounds in a different location of the parking lot that I was situated 1/4 miles away form the tower. Close to a building seem to deflect the waves and wind sometime is affecting as well. In this setup, frequency of the oscillator in the bug is correlating to the voltage it’s getting form the antenna.

I have relocated to another location that was about 1/2 mile away from the tower and the bug still made some sound in some position and location. It was more faint sounds but it is amazing how far this device can harvest energy from the tower. For this experiment, the circuit of the bug was extremely simple. Single oscillator that was set to be high frequency since I was expecting low voltage and current from the harvesting organ.

I am now located in Philadelphia so I will make another harvesting organ for new bugs that is native to Philly radio towers. Many experiments to come.