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Old 10 August 2012, 08:16   #11
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Andy if the transducer was angled wrong this could be the reason. as the water gets deeper the signal would cover a wider area and the bounceback would also give a wider signal so would hit the transducer. However as you get shallower the signal would narrow and the bounceback might be missing the transducer.

However I will say that I am guessing and this might all be complete bollix ;-)

Before you moved the transducer into the hull did you have the same problems?

Is it a dual frequency transducer. If so can you try setting it to just one frequency to test?

Chris
No I'm with you Chris, mines a Garmin 178c, dual frequency. If the transducer isn't lined up so its horizontal I lose the depth in shallow water, if it is its all good
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Old 10 August 2012, 11:05   #12
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Andy if the transducer was angled wrong this could be the reason. as the water gets deeper the signal would cover a wider area and the bounceback would also give a wider signal so would hit the transducer. However as you get shallower the signal would narrow and the bounceback might be missing the transducer.

However I will say that I am guessing and this might all be complete bollix ;-)

Before you moved the transducer into the hull did you have the same problems?

Is it a dual frequency transducer. If so can you try setting it to just one frequency to test?

Chris
That's a good idea Chris.

Yes it is dual frequency and I have tried it on both frequencies. The transducer is sat on the inside of the planing pad, so I would have thought this pretty horizontal whilst underway and at rest.

From memory the transducer emits an elliptical pattern and on the transom mounted bracket this was originally mounted to, had the facility to turn up to 90 degrees so that the pattern could go front to back or side to side. Perhaps it's worth turning this to see if I can get a better result.
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Old 11 August 2012, 01:30   #13
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I just don't understand why when reading depths greater than 35' it works fine.
Most likely a timing issue. Your system probably isn't handling the signal returned with little delay (i.e. shallow water.) give it enough time to recover and it works OK. Why that would be may be due to a lot of things, and I couldn't make a guess as to which is most likely. Doubt it's a power issue, as that's the same no matter what depth (though the return signal isn't.)

Leapy: The LF side is used for deep water. might want to think about a new marine engineer.


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Old 11 August 2012, 05:13   #14
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So if it's a timing issue I guess I have limited options.
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Old 11 August 2012, 06:37   #15
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Have you checked to see if there's a firmware update for either the DSM 25 or the head unit? I have a DSM 300 which had loads of gremlins which were sorted with updates.
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Old 11 August 2012, 07:35   #16
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I'll look at the firmware over the weekend.

What I have found out is the transducer I've got installed says it shouldn't be used at 50 khz and as my sounder is dual frequency 50 and 200khz and I've been using it on auto settings I might have fried my transducer a little.

what do you guys think?
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Old 11 August 2012, 08:52   #17
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I would get the right transducer and start there. Sounds like it is the problem.
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Old 11 August 2012, 09:56   #18
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I would get the right transducer and start there. Sounds like it is the problem.
Yes, that's what I'm thinking.

Out of interest, does anyone know what the effect would be by pumping in the the wrong frequency?

It's obviously working to some degree, it's pinging out sonar and as it's working in deeper water.
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Old 11 August 2012, 13:08   #19
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Leapy: The LF side is used for deep water. might want to think about a new marine engineer.
More likely is I need to remember what he and Garmin say rather than transpose their diagnosis ;-)
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Old 11 August 2012, 13:12   #20
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Yes, that's what I'm thinking.

Out of interest, does anyone know what the effect would be by pumping in the the wrong frequency?

It's obviously working to some degree, it's pinging out sonar and as it's working in deeper water.
If I remember right, the heart of a transducer is just a crystal. Converts an electric signal to mechanical, and vice versa. Wrong freq shouldn't do much to it, I'd think (but I may be wrong here), just wouldn't work as expected.

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