Space Age Electronics depth Below Trabdsucer - Depth Sounder 160F

[RachShep]

Hi, Any help would be amazing. We found this depth sounder which was o our boat, and we are trying to understand how to set it up. I understand how to read it based on it has two lights, and depending on which one is lite, depend if you are reading the inner or outer numbers. However the bottom dial 'Gain' I don't understand what it is for. Any help or information would be great! Image below is of the Depth Sounder

 

[AntarcticPilot]

It's very like the old Seafarer depth sounder. The Gain knob does just what it says - that is, adjusts the gain in the amplifier that receives the echo. Basically, the greater the depth, the higher the gain needs to be. But if it's too high, the flashing light triggers too early as the electronics get swamped by the transmitted signal. Modern electronics looks after all that automatically; indeed, even with equipment of that vintage they knew how to do it, but it might have needed an extra transistor!

 

[LittleSister]

When it's running properly a thing inside whirls round and a light flashes somewhere around the circle to indicate the depth against the adjacent printed scales. It may be primitive, but it does the job, and is better at giving an immediate impression of changing depths (often the most important thing) than the digital readouts on most more modern kit.

The 'Gain' controls how sensitive it is, and needs to be adjusted periodically according to how much the underwater signal is dissipated by e.g. amount of crud/creatures etc. in water, nature of the seabed, and whether modest or great depth. If you have lights flashing all around the circle, or over too wide an arc, or in several places at once, then turn down the gain. If you can't see any light flashing at all, or it's not flashing regularly, then turn up the gain until it shows fairly consistently.

The two scales enable the device to indicate over a very wide range of depths. You need to know whether you are in very deep or shallow water to know which scale to read off. (Given the great difference between the two depth ranges' starting points this is rarely, if ever, a problem.)

Essentially, the distance between the 0 and where on the circle the light flashes reflects the time delay between the signal being sent by the transducer and received back after echoing off the seabed. Imagine if you were sailing from shallow water out to sea somewhere the depth kept increasing at a steady rate to great depth. The flashing light would gradually proceed all the way round the dial and once it reached the top (i.e at a depth indicated by the maximum of the first scale) the delay would be so long it would start going round again. Now you read off the second, deeper scale.

Hope that helps. Enjoy your fathoms!

 

[peteK]

These type of sounders will also give you an indication of the type of seabed when you know what to look for,useful if you intend drying out.