Depth Sounders

[Ed Colonna]

My knowledge is fairly limited when it comes to depth sounders. I have an old depth sounder in my day sailer that looks very retro and old, the old owner had it and its never worked, looks more like a clock than anything else. However after doing a spring clean I came across what I could only think is a transducer in the skin of the hull. Does anyone know whether you can wire up any ordinary digital display system to the transducer or do they have to be brand specific as I can only presume that a transducer is commonly bought with the specific branded display system e.g. Garmin.

Many thanks.

 

[l'escargot]

Some are interchangeable. I had an old Seafarer transducer bonded into the hull of one boat I had and it worked on a NASA Target digital display installed subsequently.

 

[J Neeves]

Current 'cheap' depth (and speed) transducers are all made by Airmar. Garmin, Raymarine and Navico all supply the Airmar product for the bottom end of the market and have been doing so for years. So if the transducer simply indicates depth, and maybe temeprature, its almost definitely an Airmar product. But I'm not sure when Airmar muscled in to dominate the market. Its changing now as some transducers are a lot more sophisticated and I do not know, not having one, whether these 'fishfinder' transducers are also Airmar. But they are meant to be NMEA compatible so even the newer ones might be universal (though I confess to some, or a lot, of scepticism over NMEA compatibility).

My understanding is the simple ones are interchangeable.

But do not get too excited - they do not last forever.

Might be worth looking at the Airmar website.

Jonathan

 

[William_H]

The old depth sounder has a motor driven neon light that rotates around the periphery of the "clock" This rotation is timed to the pulses sent out to the sea bed and the speed of sound through water. So that at 12 o'clock the pulse is sent out. The received pulse activates the neon with a flash of red light. The distance the neon has travelled around from 12 o'clock is an indication of depth. It was a fairly crude form of depth sounding. The operator has to decide if the flash he sees is from the bottom or from a shoal of fish and the flash can be influenced by a soft bottom etc. Modern digital readout sounders have to decide internally if a reflection is the bottom or some false echo. Usually they do that OK. More sophisticated "fish finders" will give a picture of what reflections are recived at what depth with a record of recent reflections to give a picture of possible fish groups.
As said the transducer is interchanebale with the NASA system at least.
Me? I have never had a depth sounder except for that stout GRP and lead device hanging below the hull. It can be very positive in idicating if the water is too shalloow.
good luck olewill

 

[Fantasie 19]

My knowledge is fairly limited when it comes to depth sounders. I have an old depth sounder in my day sailer that looks very retro and old, the old owner had it and its never worked, looks more like a clock than anything else. However after doing a spring clean I came across what I could only think is a transducer in the skin of the hull. Does anyone know whether you can wire up any ordinary digital display system to the transducer or do they have to be brand specific as I can only presume that a transducer is commonly bought with the specific branded display system e.g. Garmin.

Many thanks.

May be the transducer is broken rather than the display???

 

[Oldhairy]

If the head unit is a big ugly grey unit with a big round dial graduated 0-60 feet and fathom it is probably a Seafarer as mentioned above. It is interchangeable with the NASA units. Don't throw the old head unit away. If you have to move in rivers with a lot of debris nothing else will show you the bottom. Digital will just flicker numbers.