YOUR ELECTROMAGNETIC RADIATION DETECTOR
In all likelihood you own an electronic device that can detect lightning discharges in approaching thunder storms as far away as the Mississippi River. While still out of range of audible thunder, you will be able to tell if the lightning is in a large system, or in isolated storms. In the latter case it can tell you their general direction from you.
t further it will detect the unique patterns of the stray RFI (Radio Frequency Interference) transmitted from light dimmers, fluorescent lights, TVs, computers, calculators, tablets, cell phones and really any active electronic device.
A recent use of the device was to locate where to drill a hole in a living room floor for a gas fireplace valve. That consisted of first placing a cell phone on the floor at the desired valve location. There it served as a transmitter of RFI. Then, by moving the detection device around on the basement ceiling, it precisely picked up the radiation pattern of the cell phone when directly below it. The valve is now located within a couple of inches of where it was wanted.
So what is this marvelous and useful RFI detector? It’s an old fashioned AM (not FM) transistor radio. Tune it to the high end of the band and try to find a tuning where there is no radio station, or at least a very weak one. Radios have AGC (Automatic Gain Control) which means that they greatly turn down their sensitivity when tuned to a strong station. However, when off-station, their sensitivity is very high. That is why the combination of lightning’s powerful radio transmission bursts and the radio’s high sensitivity can detect the lightning when far away.
It’s tough to find a place where there’s NO stations in the Summer time when AM radio frequencies travel a long way, but do your best. You can still readily hear the bursts of static from lightning strokes once you get used to listening for them. When far away you hear quick, weak bursts of static. When the storm gets closer, you hear louder and more prolonged bursts because lightning does not really consist of a single discharge, but rather a whole quick series of them.
BTW, these radios are somewhat directional, with the strongest pick up when the radio is end-on toward the source, so you can use that to determine the general direction of an isolated storm. If you get a continuous series of discharges no matter where you aim, you can be sure that’s a good-sized system.
It’s fun to bring your detector up to different electrical and electronic devices in your home and hear the unique and surprisingly strong signal you are getting from many of them. If near a laptop, for instance, the sound pattern alters when you change what the computer is doing. Even when a TV is supposedly off, of course, you will still detect some electronic activity working away so it can detect a signal from your remote control.