Transducer location question

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Falling Star

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I want to add a fish finder and have been thinking about where to locate the new transducer.

At present I have an old Navman 5100 Chartplotter installed, which I intend to keep. What is the minimum distance between transducers I will need to ensure that they don't affect each other?
 
I’m not sure about the minimum distance but I fitted a fishfinder transducer connected to my Raymarine Axiom Chartplotter without any issues. It was fitted in the bilge below the cockpit and internally (although designed to be through hull). About 1m in front of prop. Made a dam from playdough, poured epoxy resin in bottom, then fitted the transducer and poured more epoxy to cover. Ensure no air pockets. Works fine and accurate.
 
Put the transducer in a plastic bag of water and try it in different locations. If one is 150kHz and the other is 200kHz this will help.
If they are on opposite sides of the keel this will help to prevent direct transmission between transducers but the reflected signal will still potentially affect the other transducer. Hopefully the new fishfinder might have an algorithm that will reject random readings that are vastly different to the general trend. Only a trial run will tell you.
You might have to just turn off the one you are not using.
I have an old whirly one with the 150kHz transducer in the front of the keel and a 200kHz numerical unit amidships and they do not interfere.
 
I use my fish finder (as supplied with a Raymarine MFD) mainly for anchoring. It's very useful for finding clear patches among weed for anchoring. So I would recommend installing the transducer as far forward as you can, so that it sees the area where the anchor will be dropped.
 
Aquanaught said:
I’m not sure about the minimum distance but I fitted a fishfinder transducer connected to my Raymarine Axiom Chartplotter without any issues. It was fitted in the bilge below the cockpit and internally (although designed to be through hull). About 1m in front of prop. Made a dam from playdough, poured epoxy resin in bottom, then fitted the transducer and poured more epoxy to cover. Ensure no air pockets. Works fine and accurate.
Click to expand...
Which transducer did you fit ?
 
Falling Star said:
I want to add a fish finder and have been thinking about where to locate the new transducer.

At present I have an old Navman 5100 Chartplotter installed, which I intend to keep. What is the minimum distance between transducers I will need to ensure that they don't affect each other?
Click to expand...
What do you plan to fit ?
 
Falling Star said:
I'm thinking of fitting the Garmin Striker Vivid 4cv fish finder. This is supplied with a GT20-TM transom mount transducer but as it won't be suitable for my boat I was planning on fitting a Garmin GT15M-IH to the inside of the hull instead.
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The GT15M-IH is a good choice, at 85-165 kHz it's unlikely to clash with an older transducer.
 
Aquanaught said:
I fitted the P74 (puck type dual frequency 50/200 kHz). There are restrictions on suitability - thickness of hull but worked fine on my Bavaria. adapter cable kit for correct plug available.
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That's a traditional transducer, if the OP was fitting one of those it could clash with his Navman transducer. Airmar used to give instructions pretty much identical to how you fitted yours, a good solution that avoids extra holes in the hull (y)
 
The primary objective is to ensure a difference in the frequency of the two transducers. By achieving this, the transducers can be positioned quite close to each other without any interference.

A backup depth measurement is important, especially on an aluminium boat cruising remote places. Therefore, I have installed two depth transducers on the last two yachts. One transducer serves as a conventional combined speed/temperature/depth transducer, while the other is a fish finder. These transducers are mounted approximately a foot apart without causing any interference.

Edit: I have just measured the distance between the centres of our transducers on our current yacht. It is 200mm.
 
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The distance between the depth transducer at bow and additional fish finder transducer I fitted is at least 5m and no issues of clashes. However I guess much will depend on size of boat, keel configuration and power of the respective transducers but will the OP’s Navman accept other than traditional transducer?
 
Aquanaught said:
The distance between the depth transducer at bow and additional fish finder transducer I fitted is at least 5m and no issues of clashes. However I guess much will depend on size of boat, keel configuration and power of the respective transducers but will the OP’s Navman accept other than traditional transducer?
Click to expand...
It's 20 years old and only accepts basic depth data over NMEA0183, so it'll be traditional. The one he's considering is a modern CHIRP transducer operating at 85-165 kHz, so it's unlikely to clash with an older transducer.
 
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