Is this a transducer? Can I re-use it?

[richard_b]

Hi All, looking for some advice.
I have recently purchased a wooden boat (1970 Cox & Haswell Pegasus 35) & one of the previous owner stripped it somewhat of electronics etc. I need (well really really want!) a depth sounder & found this what I think is a transducer already through the hull. I zoomed in on the photo and that is a cable sticking out of the top that has been chopped off. So question is - is it likely I can re-use this rather than drilling a new hole or fitting something else in this hole once the boat is lifted out etc? Are they transducers universal in that most depth sounders would take a feed / input from this?
Thanks for any help you can offer! **note having trouble getting the pic uploaded - will try again soon..
Richard

 

[Tranona]

Highly unlikely to be of any use. Transducers are not universal so you need to check what it was originally connected to. Also the cable needs to be one piece from the transducer to the instrument. Most modern instruments use Airmar transducers except NASA and if you are buying new they come with the correct transducer.

 

[richard_b]

Thanks for the reply. I should have guessed really. At least hopefully I can use the same hole!

 

[bedouin]

It is hard to say without knowing what electronics it was attached to. I think older equipment tended to use 150kHz transducers and some modern equipment still does. For example I believe NASA still use 150kHz. When I bought my boat it had an old Seafarer depth sounder installed and I replaced that with a Corus that used the same transducer (150kHz)

Joining transducer cables is also possible without major issues - it is only 150kHz not radio frequency.

 

[srm]

Joining transducer cables is also possible without major issues - it is only 150kHz not radio frequency.

Probably not a good idea. The transducer has a piezo-electric crystal that generates the sound frequency. The wire simply carries an electrical pulse to and from the transducer. The return echo vibrates the crystal and generates an electrical pulse that is significantly weaker than the transmission pulse. This has to be amplified before processing by the display unit. Any power loss in the cable will reduce the sensitivity of the sounder.

Also, while its 30 + years since I last installed a transducer, I am fairly sure the instructions warned against shortening the cable. Not sure why - it may be that the cable resistance was matched to the transducer.

 

[richard_b]

Thanks for the details gents, I think I will just have to bite the bullet and go for a new one.

 

[bedouin]

Probably not a good idea. The transducer has a piezo-electric crystal that generates the sound frequency. The wire simply carries an electrical pulse to and from the transducer. The return echo vibrates the crystal and generates an electrical pulse that is significantly weaker than the transmission pulse. This has to be amplified before processing by the display unit. Any power loss in the cable will reduce the sensitivity of the sounder.

Joining cables is not rocket science and the transducer only works at 150kHz. Any good connection that maintains the shielding is not going to have a significant impact on the signal. I would not use a chocolate box but any connection suitable for low power shielded audio signals is probably fine. I certainly have a join in mine that causes no problems.

Not guaranteed of course but hard to think of a reasonable design where the length of the cable is significant (because such a design would be sensitive to lots of other factors)

 

[paulbrun]

I have an in-hull depth transducer, which was fitted shortly after I bought the boat 12 years ago, and has been very reliable. However, last week the display started flashing 'LAST' intermittently, and I am wondering if I might need to check/change the oil bath it sits in..? I am not sure what make it is, but probably Raymarine, like the rest of the instruments. The hull is wooden, 1.5" carvel planking, and the depths shown have always been very accurate, so I don't want to change anything..? I think they used baby oil when it was installed. Sorry for not starting a new thread..

 

[SP2]

Hi Richard. You've got a great boat there! I had a C&H 33 TSDY - Spectrum Too - so I know you'll have plenty to keep you busy and no doubt will be visiting the forum frequently!

Where are you keeping her?

 

[richard_b]

Thanks Mike - I'm happy with my purchase so far but as you say will need constant TLC to keep her going - she is very much as per the brochure back in 1970 I think! The boat is on a mooring in Hayling Island, Chichester harbour. I just found a youtube video of Spectrum Too - very nice indeed!

 

[SP2]

The constant TLC will be worth it. Good luck with everything.

 

[oldharry]

It is hard to say without knowing what electronics it was attached to. I think older equipment tended to use 150kHz transducers and some modern equipment still does. For example I believe NASA still use 150kHz. When I bought my boat it had an old Seafarer depth sounder installed and I replaced that with a Corus that used the same transducer (150kHz)

Joining transducer cables is also possible without major issues - it is only 150kHz not radio frequency.

Modern echo sounders work at anything from 80khz to 200khz or more. Expect significant loss of sensitivity if 'detuning' it. Or not, if you are very lucky! Mine is dual frequency (80khz and I think 220khz which allows greater depth or greater accuracy. Joining cables is not rocket science, but what sort of shape are the conductors in after many years exposed to salt damp atmosphere in the bilges?. Ok if it was tinned, but otherwise it could be quite difficult to get a good connection. Then what sort of condition is the crystal in anyway? Yes it is /should be fully sealed, but we all know how damp can penetrate older gear. Re-using the hole is the simpler option imho, and even they are not standard....