Depth sounder problem

[richlear]

The depth capability is directly related to the frequency and therefore transducer size for any given beamwidth. Better range means a lower frequency and therefore larger transducer for a fixed beam. Increase the beamwidth (and therefore spatial resolution) and you get to use a smaller transducer....

it is all about finding the right combination. There are units that will ping (and receive) through the hull but the impedance and characteristics of the GRP can have a large effect on performance.

Flow noise can also seriously degrade performance especially when flow changes from laminar to turbulent caused by either speed or hull characteristics.

Having said all that, the reality is that you will want something off the shelf at a decent price!

PM if you need some help

Rich

 

[Mrnotming]

Help from AIRMAR re echo sounder FAQs

Our old NASA sounder appears to be finished - it keeps altering display. Am I right in assuming that the instrument as opposed to the transducer ? If so can I just buy the instrument ? Also wondering about fishfinders. I've never even seen one. Are they any good ? Is it better to buy separate depth & finder ?
Thanks in advance.

Good advice from all the posters so far and here is a link to AIRMAR's FAQ page!
They make the transducers for many of the Echo Sounder/Fishfinders on the market.
http://www.ybw.com/forums/images/smilies/wink.png
http://faq.airmar.com/index.php?action=show&cat=1

 

[dunmor]

can you mount a tranducer inside a wooden hull?

 

[richlear]

In theory, yes. However, the losses transmitting and more critically receiving may be such that the signal-noise ratio is not enough for a decent bottom return especially on softer sea floor materials and in complex water columns where the sound is attenuated and scattered significantly more than in benign conditions.
The material itself plays a big part in this, the density, air cavities and impedance (which is frequency dependent) all have an effect.

Bottom line - if you want the most efficient operation you need to minimise these effects which means a hull mounted transducer away from flow noise, away from other noise sources (engines, gearboxes, pumps etc) combined with short cable runs.

cheers

rich

 

[25931]

My thanks to everyone - I've ordered a fishfinder.