#5478--MAKE YOUR OWN ELECTRONIC FISH SENSOR AND CATCH MORE
by James G. Busse
Trout by Telemetry

You can go from a frustrated bobber-watcher to a space-age fisherman in only a few evenings. That’s all the time it takes to build this project. By next weekend you’ll be able to lure the fish to your line and detect even the feeblest nibble from trout, pike, pickerel, bass or other fish you’re after. Here’s how it works: Floating on the surface of the water is the main electronic unit called a “sonobuoy.” It contains a fish lure that generates a steady high-frequency electronic signal for about 10 seconds each time the sonobuoy is rocked by wind or a wave. This signal is then piped down to a saucer-shaped underwater hydrophone, suspended directly below the sonobuoy at the end of a length of speaker wire. The hydrophone’s speaker converts the signal into high-frequency sound waves, which travel through the water for a considerable distance in all directions to attract fish. At the same time, the line from your rod and reel runs through a swivel attached to the bottom of the hydrophone by means of a small magnet. When a fish strikes, a tiny mercury switch mounted inside the hydrophone is triggered by the movement, sending a signal up to the sonobuoy on the surface. It, in turn, relays the alarm in the form of “clicks” to the fisherman located in a boat or on shore by way of a transistorized radio transmitter inside the sonobuoy. By listening to a radio receiver near you, you know exactly when a fish is taking the bait. You also hear the random 10-second signals sent out by the sonobuoy’s electronic fish lure.
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