New depth sounder transducer for furuno network

[BartW]

In my boat is a old Furuno depth sounder, this is not connected to the Navnet 2 network.

I would like to add a extra, net work transducer for the following reasons
- Can display anywhere on the network
- To have a backup, the old unit and transducer are +20yo
- this old unit gets too much interference from the electric stabilisers when they are working.
We did quite some tests on this, This is purely interference picked up by the transducer, nothing to do with the power supply, nor the cabling, unless perhaps a too long passive transducer cable.

I’m adviced by Furuno which unit to buy for the network, and would like to have this installed during the next liftout most probably in marsh.
Nobody can promise if a new unit would work with the stabs switched on, CMC say’s we never heard about that problem
Furuno say’s we don't know this problem, and we are not sure if a new transducer would be anny better, only way is to test.

I hoped that with a more modern network unit the interference protection would be better
Questions,
- any advice on interference protection for the depth sounder transducers ?
- Where is the best position to place this extra transducer, the old one is on the keel, about 2m ahead of the center of the boat length.
The stabilisers are approx. in the center of the boat, but on the sides of the bottom. Now there is approx 3m distance between the transducer and the stabs.

Any advice is much appriciated, thanks.

 

[rafiki_]

Bart, it sounds like a screening problem. Is there more you can do to improve the screening?

 

[BartW]

Bart, it sounds like a screening problem. Is there more you can do to improve the screening?

Next time at the boat Ill check the shielding of the brass transducer and its cable,
I have already checked that this cable goes straight away from the transducer to the front of the boat,
The cable (passive signal) might be too long, and work as a antenna, not sure if it is shielded cable, tbc.

it feels more as if there is "acoustic" interference, picked up by the transducer....

 

[MapisM]

it feels more as if there is "acoustic" interference, picked up by the transducer....

I see what you mean B, but if that would be the case, surely CMC should have faced the same problem at least with some of the other installations, I reckon...
Can't remember, is the existing sounder dual frequency (e.g. 50/200 kHz)? And if yes, does the interference change somehow when switching the sounder frequency?
If it's single frequency, you might try to borrow another sounder with a different frequency, plunge the transducer into the water, and see what happens...

 

[BartW]

CMC say they didn't hear about such a problem, but then we have to realise that most of their customers are Captains or crew on a big yacht, which don't even know
"how to switch off the power supply to the stab system "

also,
on big yachts, the depth sonar is not used/looked at very often (I think)
we use it quite a lot as you know, on a dive spot, and for anchoring, choosing and knowing the exact depth.

I do have a 2 freq transducer, one freq works slightly better then the orther, but not good enough,

on the display, I can see the interference, many dots, as if there are many fishes under the boat ;-)
but with a more regular pattern...

 

[MapisM]

Yep, I remember how the interference looks like, just forgot that it's there on both frequencies.
Anyway, pretty sure any Benetti (or similar) captain would turn on the sounder together with all the rest of nav toys, no matter what.
Did AC suggest that you might be the first to have spotted that? If so, he doesn't held superyacht captains in high esteem!
Sure, there's the good, the bad and the ugly (as in most other professions), but I just can't believe that none of them would have spotted an interference like that...

 

[BartW]

Did AC suggest that you might be the first to have spotted that?

not really,
He just told me that he never heard of such an issue,

but in another context he gave me a stupid examples of a boat crew / engineers they were talking with for doing diagnostics on a stab system,
and were really disappointed what a lack of system knowledge they had,
except for the user functions ofcause.
(but all nothing to do with a depth sounder)

I just can't believe that none of them would have spotted an interference like that...

yes agree, therefor I guess my problem is either;
- a old non selective depth sounder / transducer
and or
- a rather small installation, all very close...

any idea where depth transducers are usually placed on boat sizes 50....80ft ?
I could asc CMC to check this with SL and Az,
and asc again about the interference...

I think next step,
I'll order a active, network transducer, and test it in the water,
like your sugestion.

 

[MapisM]

any idea where depth transducers are usually placed on boat sizes 50....80ft ?

Well, the position you previously described sounds perfect.
I really don't think it can be a matter of moving the transducer elsewhere.

Btw, if you wish to test a new one, it's not even necessary to chunk it overboard.
Just connect it, with its original cable, and place it inside the bilge, in the position where you are thinking to fit it.
It might struggle to report the bottom correctly of course, but that's not important.
What you want to check is whether the stabs interfere or not, and by turning them on and off you can easily see what happens.
If it doesn't create interferences while left inside the hull, I can't see any logical reason why it should in its final installation.

 

[jfm]

Btw, if you wish to test a new one, it's not even necessary to chunk it overboard.
Just connect it, with its original cable, and place it inside the bilge, in the position where you are thinking to fit it.
It might struggle to report the bottom correctly of course, but that's not important.
What you want to check is whether the stabs interfere or not, and by turning them on and off you can easily see what happens.
If it doesn't create interferences while left inside the hull, I can't see any logical reason why it should in its final installation.

Good thinking. BartW I am about to receive a new transducer (an airmar CHIRP B175L with many frequencies not just the 50-200 pair) and black box (Garmin GSD26, CHIRP) that the transducer connects to. The black box then connects to the garmin network via Cat5 cable. I will not fit this to the boat until the April or May 2014 lift out so you are welcome to borrow this anytime before then, keep it for a month or so, and try it in BA. But of course I do not know if it will connect to a furuno network. I can lend you a small Garmin plotter too, then you will have a network, but all this will prove is that Garmin does/doesn't work, not Furuno, hmmm. But anyway you are welcome to borrow this hardware if you want. I can mail it to Belgium

 

[BartW]

you are welcome to borrow this anytime before then, keep it for a month or so, and try it in BA. But of course I do not know if it will connect to a furuno networ I can lend you a small Garmin plotter too, then you will have a network, but all this will prove is t
in does/doesn't work, not Furuno, hmmm. But anyway you are welcome to borrow this hardware if you want. I can mail it to Belgium

Thanks for your kind offer J, your sugestion reminds me that I have a almost new Lowrance plotter with sounder at home (to be sold) so ill first try that one next weekend
Cheers


I will anyway place a new transducer, during next liftout, (backup)
Any advice on distance between the two ?

 

[MapisM]

I will anyway place a new transducer, during next liftout, (backup)
Any advice on distance between the two ?

TBH, I don't know if there's a min safe distance.
I did fit a 2nd transducer on my boat years ago, but my train of thought was that I would have rather risked some interference than place it in a sub-optimal position.
In the worst case, I could still have used either one or the other, even if not both together. But at least, each would have worked well standalone.
Bottom line, I placed the second very near to the first, just on the other side of the keel.
In spite of that, they do work nicely also when both are turned on.

One placement you should avoid is longitudinally aligned (either in front or behind) the existing one.
Transducers work best when they are placed in an undisturbed water flow, so the one behind could struggle to work as it should.
Which means also that you shouldn't place the new one behind a seacock, or any other stuff sticking out of the hull.

 

[BartW]

Now i remember,
on the karnic I had 3 transducers, at the stern, less then 40cm between them, and they could all work simultaniously,
One was the orriginal raymarine, and for a while I had a extra Lowrance plotter with depth and sidescan sonar,
And this worked all together without interference

Agree with the longitudal position, in undisturbed water

 

[Bilgediver]

Bart, it sounds like a screening problem. Is there more you can do to improve the screening?

My thoughts exactly Maybe kitchen foil in the right place !!!!

 

[BartW]

just to report that the Lowrance depth sounder works very well, also with stabs switched on,

BUT,
the old Furuno also works at one freq (50Kz) , not at 200Khz,

I was fairly sure that I have tested this before, so don't know what is different,
MapisM don't you remember ? I think you were there when we did the tests not ?

now I realise that the price for a Furuno network sensor is very steep,
especially for upgarding a "old" network system.
But I believe I have to byte the bullit, as I want it anyway.
will wait for the boat show in Dusseldorf.

 

[BartW]

on a 57' boat i'd want an open array scanner, which is another big cost.

this post is copyed from Nick's wonderfull US trailable sport fishing boat !

Nick, why do you want an open array scanner,
I would love to have one myself, but could never justify the cost,
as there is so little usage of the radar,
and the smaller dome version (4Kw iirc) does the job perfectly in the few occasions that I'm sailing at night ?

looking for second hand / ebay is an option...

 

[MapisM]

I was fairly sure that I have tested this before, so don't know what is different, MapisM don't you remember ? I think you were there when we did the tests not ?

Yes indeed, we did some check together, when we met before the FDC.
But sorry B, I can't for the life of me remember if we tried both frequencies.
That's in fact the reason why I asked, in my previous post #4...

I fully agree that it's a good idea to fit a 2nd transducer connected to the NavNet instruments, anyway.
You might check US prices, which are usually much lower.

 

[MapisM]

Nick, why do you want an open array scanner, I would love to have one myself, but could never justify the cost, as there is so little usage of the radar, and the smaller dome version (4Kw iirc) does the job perfectly in the few occasions that I'm sailing at night ?

+1. From a functionality standpoint, open array radars are extremely hard to justify on any pleasure boat, other than those meant for ocean crossing.
The increased range vs. the smaller radomes is totally useless for collision avoidance, and can only make sense for spotting thunderstorms on long passages.
Otoh, digital vs. analog, that's a different matter. The first does give a bit "cleaner" image, particularly if compared to an analog radar not properly tuned.
Then again, also with digital, the increased range of open array does not have any practical use, in the Med.

 

[Nick_H]

Nick, why do you want an open array scanner,
I would love to have one myself, but could never justify the cost,
as there is so little usage of the radar,
and the smaller dome version (4Kw iirc) does the job perfectly in the few occasions that I'm sailing at night ?

You're right of course, there's no good reason to have one. In 6 years in the med I can count on one finger the number of times i've really needed radar, so it would be crazy to buy one when a radome would do the job fine for my purposes. My post didn't explain my thought process very well, it was more a factor in the comparison, to replace what I have now with equivalent new equipment would be £15k, because I have an open array at the moment. I also wondered whether a buyer would expect to see an open array when I come to sell, hence the "on a 57' boat" comment. It wasn't the main factor that put me off upgrading.

 

[MapisM]

I also wondered whether a buyer would expect to see an open array when I come to sell, hence the "on a 57' boat" comment.

In spite of what I previously said, I must admit that you have a point in this respect.
For some reason, the very large majority of boaters seem to think that open array radars can make a boat more seaworthy... :nonchalance:

 

[jfm]

MapisM, each to their own of course, but I don't agree. The principle difference is that the wider array gives far better angular resolution than a narrow array. The best domes give about 4 degrees resolution (because the whirler array is only 2 foot wide); the best 4ft arrays give about 1.8, and the 6 footers give I think 1.3deg.

This means that in a busy place (anchorage, whatever) you see distinct targets from quite a long way away, not a load of blobs that have merged together into a single big blob.

Now that is nice luxury, though of course not necessary on a pleasure boat. But if you accept the principle that there are lots of things that are nice to have but not necessary, then a 4 foot or even 6 foot array (an open array, of necessity) can be justified. Justified in a "boy's toys" kind of way of course, but that is true of the boat in the first place

Just on a different point, but somewhat related, you remember we discussed a while ago whether 12kw made sense compared to 4kw. Mostly it makes no sense but on one trip last year, coming back from Corsica, I saw several big rain blobs from 30 or 40 miles away, and they weren't moving or moved only slowly. I observed how their shapes developed and could see a distinct gap between two big (4 miles wide maybe) blobs of heavy rain. So I tweaked my course a couple of degrees and passed along the 1/2 mile wide corridor and had a nice dry ride! No big deal obviously, but it was fun. Separately when setting off for Corsica which is 100nm, I can look at the sky for the entire route and see if there is rain. Normally there isn't of course!

So anyway I'm not claiming any of this is essential but a 12kw x 4 or 6 foot array is a nice thing to play with and gives you some information you can use, though it wont change your life