Posts Tagged ‘sonar’

Depth Sounder

3 April 2017

Here’s another piece of equipment destined for the dustbin (or in this case, electronics disposal center). I found this a few years ago at the Goodwill Outlet in Seattle. As far as I know, it is totally functional.
It does, however, lack the transducer needed to make it work on a boat.

legacy depth sounder

Location by Echo

Radar, Sonar and related distance-finding technologies all operate on the basis of echo-location. It’s a clever system, because you can measure both distance and direction from just one point. With visual methods you need two or more points to view from so you can triangulate.

In the case of this device, the transducer is fixed to the bottom of the boat, so it only points down. Thus, “depth and fish.”

Whereas cheaper versions are geared only to tell you how much water you have under your keel, this one is rigged to display multiple echos from different depths. Judging from the difficulty I had in finding the user’s manual for this instrument, I would guess it was built and sold before internet shopping became popular. Modern versions still operate on the same principle, but are computer-based.

Here’s the electronics:

depth sounder electronics

Relatively simple. It operates on the boat’s battery, 12 volts. There’s a connection for the transducer (I moved it from the back). There’s a motor to spin the lighted indicator, and some logic circuits. If you’re into electronics, you’ll also notice some RF (radio frequency) parts on the board. Per the manual, the transducer operates at 200KHz. That’s RF, and as sound, classifies as ultrasound. It’s ten times higher frequency than what we can hear with our ears. I don’t know about fish.