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Old 14 June 2012, 11:03   #11
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Lower freq penetrates water better. Higher freq show better detail, but doesn't get as deep.

Plotter probably can fail on one freq; wouldn't expect it on the 'ducer (though I'm not sure if there are two separate channels in it or not; wouldn't think so, but might be wrong.)

As far as I know, the 'ducer is simply a bi-directional transducer: converts the pulse from the head unit to sound to emit, then converts the reflected echo back to a signal to send back to the head unit. Don't think there's anything else in there.

jky
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Old 14 June 2012, 14:26   #12
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Quote:
Originally Posted by jyasaki View Post
Lower freq penetrates water better. Higher freq show better detail, but doesn't get as deep.

Plotter probably can fail on one freq; wouldn't expect it on the 'ducer (though I'm not sure if there are two separate channels in it or not; wouldn't think so, but might be wrong.)

As far as I know, the 'ducer is simply a bi-directional transducer: converts the pulse from the head unit to sound to emit, then converts the reflected echo back to a signal to send back to the head unit. Don't think there's anything else in there.

jky
Thanks ...can I try your words slightly differently?

The low frequency 'sees' deeper water in relative less detail. The high frequency doesn't 'see' deep but what it does see is in greater detail. Sounds like I might have a high frequency failure then. This would also explain the hysteresis as the cut-off boundary would unlikely be sharp.

again
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Old 15 June 2012, 13:05   #13
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Low frequency sound penetrates water better, so it reaches deeper. Fishermen use lower freqs for water deeper than about 180 feet.

High freq gives better detail, doesn't reach as deep, but we're talking more like < 200 feet, rather than < 20. I suspect you do not have a complete channel failure.

Should be able to select which freq you send out (in the sonar settings of the head unit), which would allow you to test the independent channels.

If you can get someone with a similar unit, try swapping transducers and see if that corrects it. Or head units.

One other thing: You may be seeing interference from some other electrical system picked up in the transducer cabling. I'd expect the effect to be more pronounced with short delay time signals (as when the echo returns quickly; i.e. skinnier water.) If you can easily get the cabling away from everything else, it might be worth a shot to relocate it apart from all other cables, at least long enough to try it.

Luck;

jky
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Old 15 June 2012, 15:22   #14
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Hmmm, interesting.

I was beginning to think my 'ducer was starting to play up this year, but the symptoms sound very similar to yours Leapy. Last year I am sure I used to get a reading at about 4' depth or so, but this year it is very erratic and sometimes doesn't start reading until 15' plus (stationary or underway). This is not great for me as the channels into my beach mooring are down to 4' depth in places . It also loses contact with the bottom more readily when going along and just flashes the last known reading. If it doesn't find a depth from first turning on it flashes blanks IIRC.

I had started to assume my 'ducer was playing up or maybe running out of glycol/oil in the housing bonded inside the hull. However all checks out ok and the only thing that has changed is a software update to the plotter (GPS5008), fitting trim tabs and AIS to the boat. The clicks from the 'ducer sound louder than I recall too .
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Old 15 June 2012, 18:03   #15
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I've arranged an appointment with a marine electrician for the end of July when we're next on the water. In the meantime, I'm tempted to send the plotter back to Garmin for them to check as they've offered to investigate.

There's nothing else I can do in the meantime as the boat is well and truly on dry land and we're about as far away from the sea here as it's possible to get in the UK.

Erin - interesting, although the problem very definately didn't start for me with a software update. I've only updated in an attempt to try and fix it, with no result.

jky - the boat in this context is as built nearly four years ago. Plotter in the console, cabling into the hull trunking along with all else and exiting with the outboard and steering stuff just forward of the transom well. Nothing has changed in that respect. In fact, the only thing on the boat to change since build is the fitment of a keel guard through which the transducer must 'see'. However, this brings it into line with most boats built by Ribcraft - our keelguard was retro-fitted by Ribcraft - rather than making it somewhat different. The issue I'm having is unknown to Ribcraft.
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Old 24 July 2012, 03:20   #16
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Did the replacement part trial yesterday with new transducer/new plotter.

Bottom line - original plotter knackt, presumed the shallow depth frequency is down. Returning the plotter to Garmin ... 140 to fix :-(
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Old 01 September 2012, 03:06   #17
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Quote:
Originally Posted by Leapy
Did the replacement part trial yesterday with new transducer/new plotter.

Bottom line - original plotter knackt, presumed the shallow depth frequency is down. Returning the plotter to Garmin ... 140 to fix :-(
Returned the (four year old plotter) to Garmin who were unable to find anything wrong. Having said that, turns out they can't test sounder performance as they're land based and can't simulate.

They exchanged the unit for a refurb unit at no charge so we'll see how that performs.
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Old 21 October 2012, 14:17   #18
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New (refurbished) Garmin 551S fitted and problem solved

No words of explanation from Garmin but the replacement was FOC even though the old unit was three years out of warranty :-)
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