transducer wire splice

[TollyWally]

To snake my new transducer cable through existing access holes using the old cable as a messenger I need to clip off the factory plug then reattach. The rather vague directions in the box mention a waterproof junction box. This leads me to believe it's not that big a deal.

My preference is to solder it back together. My boat has an enclosed pilot house so water proofing is not as critical as some boats. Although if soldering I would use standard waterproofing technique, shrink tubing and liquid tape.

I don't have much fear with ordinary wires just carrying juice but transducer cables and antenna leads etc. seem mysterious with lots of doubts about shielding, interference etc.

What is the consensus on proper procedure?

Thanks,
Wally

From an electronics perspective, what you need to be careful of:

Not shortening the signal line. Sonar is about timing. Enough change in the length of the cable can cause the unit to stop working. However... I don't know what that length is. Splicing an RF cable is a big NO-NO. If you need to shorten or cut the cable, do it at the connector end. I would extract the pins, or desolder the end that goes into the head unit if I were going to attempt it.

I spent 23 years in the Navy as an elctronics technician and later as an electrical engineer. I spent the first 8 years of my career as a antisubmarine warfare technician and worked exclusively on sonar detection systems on planes. In my last tour, I ran the Navy's Advanced Technical Engineering Command at Whidbey Island where the Pacific Fleet's ASW forces depended on us to answer questions just like this.

When I bought my unit 2 years ago... the first question I asked our guys was "Hey... ya think it hurt to cut the cable end off and reattach it?"

They scratched their heads and said... "Those things are expensive... Can't you cut a bigger hole in the boat?"

Can you cut a bigger hole in the boat?

[kwb]

Proper procedure is to drill a bigger hole.

[Seapuppy]

I guess I'm missing something here...he asked if he could cut and splice the leads back together...why is it required to cut a bigger hole somewhere???....
it's better to keep a lead in one peice but a splice should be acceptable as long as the shielding is resoldered back and the leads are properly insulated for corrosion and connectivity..........
your only talking a unit that is a few ft with a lead that is not moving alot of pwr or shouldn't have a build up resistance from length of wire...so...a good splice should be ok but make your splice up in the dry area of the boat...not near the bilge....
:argh arrr

[heymagic]

He actually asked if he could cut the transducer cable in order to run it through the existing old cable holes. The proper, recommended procedure is to make the existing holes bigger. I believe every DS manufacturer says not to cut the cable. DO NOT CUT the cable.

I have cut TD cables and spliced them back together though. In fact I added a second lead to one so I could move the head from flybridge to lower helm. It worked. You run the risk of interference through the breach in the cable, as well as the possibility of corrosion in the future.

So, back to the old saying...just because you can doesn't mean you should...

I will not allow wrong or questionable advise in theses forums. Sharing experiences is fine, recommending something against standard accepted practice is a no-no. Spliced TD cable, boat on the rocks, someone drowns, guy on IBNW said it was ok....some attorney gets a new Californian......we can be held liable for advise given here. Be careful what you say....Please. Thanks, Gene

I guess I'm missing something here...he asked if he could cut and splice the leads back together...why is it required to cut a bigger hole somewhere???....
it's better to keep a lead in one peice but a splice should be acceptable as long as the shielding is resoldered back and the leads are properly insulated for corrosion and connectivity..........
your only talking a unit that is a few ft with a lead that is not moving alot of pwr or shouldn't have a build up resistance from length of wire...so...a good splice should be ok but make your splice up in the dry area of the boat...not near the bilge....
:argh arrr

You are missing something Steve. It's not about resistance. It's about impedence.

I would suggest NOT cutting the cable (I didn't cut mine and I hold an ISO 9000 micro-miniature solder certification as well).

You're talking about a 200Khz transducer on the end of a 20 ft cable. The signal is timed (not measured) from the head to the transducer. Any (even slight) change in the impedence or frequency response of that cable, will be seen by the head. So much so, it may not work at all... if you're lucky... it may only go off by 10% or so.

As far as power... that's a 500W transducer on mine... that's 20 times as much as your VHF. The returning signal is on the order of millivolts and is coming back in nanoseconds. There's a reason they tell you not to splice the cable if at all possible.

The "bigger hole" was to run the connector end. Mine was about 1/2" in diameter, so it was a simple task, and I just resealed with 5200 when done.

I don't mean to sound too negative about it. I'm sure it can be done. I just chickened out myself, and wanted to pass that along. It was easy to run the cable. A spade bit and a tube of 5200 and I was done in half an hour.

[TollyWally]

First off, thanks for all the timely responses! I also appreciate the cautions about going into something like this willy nilly.

Referencing some of the things mentioned by others:

1. Drilling a bigger hole
If drilling a bigger hole was a simple solution believe me I would do it. A furnace was installed over the top of the access panel which is under the settee seat. Drilling a hole may be theoretically possibe but at this time I am looking for simpler solutions.

2. Splicing, shortening cable length

Furuno and airmar indicate that the cable can be spliced but suggest using a waterproof junction box from Gem Electronics. I like to do things right on my boat but really don't want to wait around trying to get one of these specific junction boxes. Furuno mentions in a general way lengthening transducer cables but again we are back to the Gem Electronics box.

This would seem to indicate that perhaps on these small consumer grade electronics, cable length is not as big a deal as on a big ship. I certainly don't mean to argue or diminish the validity of anyone's response, especially that of a retired Navy tech! Sadly however I don't have the resources to always go 100% MilSpec.

Further more I would only be shortening the cable length by the amount of wire needed to strip back for soldering. A fairly miniscule percentage. I don't think there would be any measurable difference from the amount burned using the junction box.

3. Resistance, corrosion, waterproofness

The crux of my dillemma. This is what I worry about most. I am quite ignorant of the finer points regarding sonar, shielding, radio antennas etc.

I am a fair hand with a soldering iron and have always soldered almost all of my marine and automotive connections. I use heat shrink when ever possible and paint over the whole shebang with several coats of liquid electrical tape. I don't buy into the Coast Guard warnings about vibration and hard points and think that the yacht council recommendations about crimping etc. is mostly to provide cover for cheaper faster methods rather than best practice.

Given these precautions and the fact that my boat has a pilot house, if all the recommended waterproof junction box is for is to insure waterproofness I'm not sure I need to bother.

If interference is a problem are there low tech remedies?


4. Liability, factory admonishment about cutting cable etc.

I think we can all appreciate the problems that a diminished sense of personal responsibility and an excessive reliance upon legal remedies coupled with an aggressive lawsuit industry have caused this country.

Of course the factory says not to cut the cable. MY gps and many of my charts are not to be used for navigation. My step ladder and hammers both have warning lables. At a certain point some of these precautions are the equivilent of crying wolf. Is this one? I don't know.

I greatly appreciate the comments regarding "just because you can doesn't mean you should" coupled with the antedote that it has been done. Specific techniques would be appreciated.

In the end of course, I will have to make up my own mind. The more data points the better. Every thing I learn helps me make a better decision for myself.

Once again thanks to everyone for input.

Wally

[Go Aweigh2452]

I think Wally is getting old... he's starting to repeat himself... OK... fun time is over, lets all get back to work/play/whatever... hope this frekin rain stops soon. I have stuff to do outside and the Admiral wants stuff for me to do on the inside... I'd rather be wet however...

I'm just trying to pass on that this is an RF cable you're talking about. 200Khz is on the lower end of things, but it is still that. Understanding the differences between impedance and resistance is important. Shielding is important, cable length is important. The way it's repaired is important and signal loss is critical.

You chose what you wish. Let us know how it works out. I agree the easiest way, would be to simply splice it... but if you wouldn't do that on your VHF radio... understand there are reasons you wouldn't do that on a 200Khz transducer as well.

And for the record... I'm not talking about Sonar on a ship where you're looking at hundreds of feet of cable. I am talking about sonar and hydrophone units that are dropped from planes and are 6" in diameter and 42" long.

I know that drilling a hole isn't an easy operation, but I can't see how it's impossible on any boat... or enlarging the one that's there currently.



Drilling a hole may be theoretically possibe but at this time I am looking for simpler solutions.

I'm sorry if my answer isn't the easy one... but there ya have it.

[TollyWally]

wow, I think somehow I got the review and submit buttons confused. Quite embarrassing.

Attn: Moderator delete excess posts if you want (please)

If I thought I could drill a hole in an hour or two I'd do it.

No other routing possible?

Wally, here's my $.02: If Furuno and Airmar say it's OK, do it. My recommendation is that you call Airmar and ask them specifically about cutting and soldering vs. using the Gem Electronics box. They are the transducer manufacturers and, as such, should know more about this specific application than anybody on this list.

Raul

[Seapuppy]

Gene..I'm not advocating doing anything that would hurt the guy....I'm saying that as a sub designer...splicing is a practice that has been going on for alot of yrs and that done properly can be safe...I never advocate anything unsafe..just trying to understand the question....
as far as the sign ratio and impedence...it isn't going to change much if you splice properly....if any at all.........so...follow the recommended directions of the manufacturer and it should be ok........
the other option might be to desolder the plug if it's possible and run the cable then resolder it back properly.....no change in impedence if that is the worry for this unit...
another option might be to get another plug and snip the old one off...run the cable and attach the new plug....again..no change in impedence and it's a safe install......
.I'm not familiar with his unit but just to say drill a hole is the only option....well..there are others.... :argh arrr

as far as the sign ratio and impedence...it isn't going to change much if you splice properly....if any at all.........

Steve... you're still talking about common resistance. Impedence in an RF cable is a completely different bird. There are reasons you don't splice RF cable. On a copper conductor of any kind that carries AC (RF in this case) the wire is simply a conduit... the signal will build and reflect on any imperfections along the way. If they build a unit around a known 20' of cable... with no splices or connectors, then it's impedence-matched for that. Any changes will only degrade the signal.

You can install connectors on any RF cable, but each adds to the total impedence and loss. And as a sub designer... you did lines on paper. Simply "splicing" RF cable is poor advice. These aren't just wires. Don't forget that. You're building an AC 200Khz signal which stimulates a piezo-electric device down the cable (the 'ducer). The ultrasonic signal is then sent to the bottom at around 70% the speed of light, it's reflected back where a TINY amount of energy is felt and converted back to milliamp AC 200Khz and sent back to the head. The differences are so slight in timing, that it can detect and discern the density of the oil in a salmon's gut against the contrasting sea water some 600 feet away. You think you can solder a wire to build a connection that is electrically invisible? I'll have to show you a cool toy called a Time Domain Reflectometer (TDR) or a Frequency Domain Reflectometer (FDR). I used them for 23 years. You can actually "see" things like solder joints, crushed cables, stripped and repaired shielding, corrosion on the shielding of a cable, or even a persons hand holding a cable hundreds of feet away.

Electronics isn't magic, but it is predictable and repeatable. You might get lucky and get a splice to work. You might even get lucky enough to not really notice much difference in the sonar display... OR... you might end up with a chuck of plastic at the end of a cable that'll cost you $120 to replace becuase drilling a hole wasn't the easiest repair.

If you could simply solder the wires back together... why in the world do you think I'd even care? Do you understand what impedence is?

Gimme a quick lesson if I'm missing something...

[Seapuppy]

Mike..don't start getting into a ****ing contest here....1) the wires going to a transducer might be impedence matched....but the length of wire is not the issue since it's less than 300ft...at that distance resistance starts becoming an issue....2)sonar does not and cannot approach the speeds your talking of in the water...it is physically impossible to have sound approach that kind of speed in a medium such as water......
3)....I know what impedence matching is......but when your talking about a length of wire less than a 100 ft....impedence shouldn't be a problem if you splice it properly....ie at the connector or to a splice box.......I'm not advocating doing a splice half assed here.....I'm talking about doing a proper splice....then the impedence won't be an issue.....
last but not lease ...when installing systems such as AN/BSY 2, AN/TRSS-355's or even TACTUS tactical towed array sonar systmes.....I know how sonar works...I know big systems too....so we both have experience in the art of sonar...but doooooooooon't get into a ****ing contest on knowledge....... :argh arrr

[tolly28]

The ****ing match started a while ago... Might be a good idea to let this one go before it goes too far. You're both very knowledgeable (way beyond me...), which I figured out long ago....

Just my $.02. Shake hands and be friends.

[Roel Jansen]

I think I have done every thing that could go wrong with wires and electricity.

The last innocent "fix" I made could have burned the house down easily.
The head of this lamp ibelow is brand new and why? Long time ago I had to change the lamp. the peice of iron that made the balance fel out into the converterbox of the central heating below.
http://community.webshots.com/photo/323908768/323912251WOWIfh

Was not in the mood of searching so I replaced it with a quarte coin. and yes it kept extactly the balance.
two months ago we were sitting nicely for the fire good wine etc when we heard a strange noise what hapened to be the head of the lamp burning and already big flames came out! OK walked it outside and stopped the frire.
Normally when we went away and come back in the evening we let this lamp burning. It has only as most of our lamps have only a wire from the main current to the trafo. As it is 6 volts only what could go wrong! now we know!
What caused it we don't know made the quarter a bad contact? It was in for years already. But what I want to state with this one liner Never if you are not qualified do anything with wires or electricity than leave it the way it was.

[Go Aweigh2452]

Yeah, you are one lucky guy... stuff happens...

Mike..don't start getting into a ****ing contest here....


I'm not Steve... I just feel you're incorrect in saying there is NO issue in cuttling a 200Khz cable.

(1) the wires going to a transducer might be impedence matched....but the length of wire is not the issue since it's less than 300ft...at that distance resistance starts becoming an issue....

You're kidding right? You make that up?

(2)sonar does not and cannot approach the speeds your talking of in the water...it is physically impossible to have sound approach that kind of speed in a medium such as water......

I was actually talking about the speed of the signal on the wire... that's what we're talking about Steve. Electricity flows at about 70%-80% the speed of light. That's why impedence happens. Any deviation in the conductor, its orientation, its magnetic field or even chemical composition can set up what's called a standing wave. This standing wave then "impedes" the signal. It doesn't actually stop it or "resist" it... but simply "slows" it . This is what they do when they impedence match a cable to a given RF circuit.


3)....I know what impedence matching is......but when your talking about a length of wire less than a 100 ft....impedence shouldn't be a problem


That's nonsense imependence is an issue in ANY length of RF cable. I know exactly what you're saying Steve... but... that being said... could you shorten or splice a VHF connector on your radio with any guarantee of success? No.


...but doooooooooon't get into a ****ing contest on knowledge....... :argh arrr

I'm not Steve. Just don't get your feelings hurt if we come down on different sides of an issue like this.

Can it be spliced? Yes. Should it be spliced or shortened? No.

Don't believe me... just call the manufacturer like Raul suggested. That's actually the best advice so far. Mine says DO NOT cut the cable. I understand why. We don't have to agree and I think Tolly28 will make the right decision for his boat and his situation. I just ran the new cable as the manufacturer suggested and it works fine. If I'd cut it... and lost the signal or missed a fish... I'd always be wondering if it was something I did.

Enough said about this one I suppose.

[heymagic]

I understand the problems with running a new cable. No body here has ran more TD cables than me. Pretty sure I'm right in that statement.... Airmar does have a junction box, 33-035, made for cable repair. THey say if the instructions are followed carefully it will result in a corrosion free , waterproof joint. So it seems they have a concern with corrosion and water intrusion. If you splice the cable yourself I think it will work, but maybe in 6 mos the signal will start degrading, or when the refer runs maybe the readings will fuzz out . Every splice or crimp in a wire puts a hard spot or stress at the endge of the crimp or solder. Any crimped or solder joint needs to be supported past those points to negate vibration. Boat hulls vibrate a bunch and the possibilty of the wire fracturing at that spot is real. Best course is to do it right.

Let me add a note about advise ....I get up 5 or 6 days a week , get dressed and go out and work on cars or boats. I've done this for nearly 40 years...now I hesitate to call myself an expert in anything...but, I make a darned good living, have a thriving business and a great reputation. If someone on this board has rebuilt a Rochester , I've done a hundred....Some Sailor has spent years being trained in electronics and systems by the Navy as well as being a multi-talented guy. If I don't know how to do something I'll tell you right up front. Always examine advise carefully and the source of said advise. Many people have dabbled or are do-it-yourselfers. They've done something once, gotten away with it and tell everyone how it's done. I see this all the time on BOC and Don S and Les have fits. Not everyone in the business or any business does things the same. There are still acceptable practices that are adhered to. Many people will ask for advise and only listen to the answer they were looking for. " Yup, I just wrapped that fuse with tinfoil and it's worked for years now"....I used to work with a mechanic who was too lazy to properly install a timing belt or drive belt. He would cut off the old one and roll a new one back on. No loosening, no tightening...unless the belt squealed. I always wondered how many people had a belt snap or jump a year or two down the road.

Well, enough of my rambling..free advise...make sure you get your moneys worth.

Thanks Gene... I tell ya... one thing i have learned is always err on the side of conservative if its something I don't have first hand knowledge of.

I didn't splice mine... but it sure was tempting. Book said no... so I did it the hard way.

I see your frustration in the pot-shot answers that get tossed out there. I'm sure you've seen more than once the results of good intentions.

[Seapuppy]

" And as a sub designer... you did lines on paper."
As a subdesigner...I did more than just put lines on a paper....
Systems integration is taking the system and installing it...testing..evaluating and approval....

" Simply "splicing" RF cable is poor advice. "

I'm advocating doing a splice if it can be done safely and with the approval of the company...ie at the connector (I'm sure it has one) or to an approved splice box....

" The ultrasonic signal is then sent to the bottom at around 70% the speed of light, it's reflected back where a TINY amount of energy is felt and converted back to milliamp AC 200Khz and sent back to the head."

it sounds like your talking here about a signal going out and down to the bottom of the water and back near the speed of light...not possible...are you talking about the wire and back to the unit???...it didn't sound like it here....


"The differences are so slight in timing, that it can detect and discern the density of the oil in a salmon's gut against the contrasting sea water some 600 feet away. You think you can solder a wire to build a connection that is electrically invisible? I'll have to show you a cool toy called a Time Domain Reflectometer (TDR) or a Frequency Domain Reflectometer (FDR). I used them for 23 years. You can actually "see" things like solder joints, crushed cables, stripped and repaired shielding, corrosion on the shielding of a cable, or even a persons hand holding a cable hundreds of feet away.".....

seen em.....also a megger!!!...checks for insulation break down...also a batch of other eqpt used on a boat used for emi measurements...




the guy asked if he could splice his cable for the transducer....I say yeah if it's done properly....not just hap hazardly...or cut and solder and then add some tape anywhere in the middle.....we're talking about a fish finder .....not a targeting type sonar such as the AN/APS-55(V)....we in the subs and surface combat ships as well as airplanes such as the 777-200 or 747-400 have spliced a cable up near the connector and then resolder the new connector in it's place after the cable has been ran thru the ways.....it can be done and no signal loss or loss of effiency.........it's not bad advice....it's a matter of my experience too......... :argh arr

seen em.....also a megger!!!.[/qoute]

Ever use one? :D

Tolly28; You've heard all the ruckus. Good luck with your install. I'd still say contacting the manufacturer and asking them what the best method is, couldn't hurt

... enough said about this.

[Seapuppy]

Dude....hence the term systems integration, test and eval........ :argh arr

[Tedster]

SP this is one of those times you just need to knock it off and stop trying to be right about this....got it......nuff said! Ted :D

We can just agree to disagree Steve. I respect your experience, and it conflicts with mine is all. Tolly28 can make his best judgement now. No harm... no foul on my books.

Lemme know when you get that satelite dish going... that one stumped us both without a cable splice :D

I'll need that bracket back to build another one for ya, so gimme a call when he's done.

[tolly28]

It was Tolly Wally that asked the question, not me....

Got your Tollys mixed up I guess. :D

For the record MY transducer is just fine. Paid the yard to mount a new thru hull (hate to have to hire stuff...). No wire routing problems here.

Somebody needs to give up on having the last word on this one.

Right now I guess it's me!

Steve

No ... Steve gets it... :D

(kidding...)

8)



Just for the record... Steve and I get along just fine. I was just on his boat yesterday arguing about satellite installations. We had a referee (Bob). We drank his soda pop, aimed his dish and we all left having seen nothing better on TV than Al Jazira. Steve has an appopintment with a satelite guy Wednesday... Shows what we know... :)

[Seapuppy]

GEez ted...this is a discussion...right??...this is where we talk about crap...right???this is us disagreeing and yet getting along...right???.....or is there something I'm missing again.....
Mikey's right....we were all on the boat having a great guy bonding thing going and then went home.....no problems....he's seeing things from one perspective...and I see things from another.....it's called sharing experiences and knowledge.......
get off your hi horse and let us discuss stuff......and stop badgering me.... :argh arrr

SP this is one of those times you just need to knock it off and stop trying to be right about this....got it......nuff said! Ted :D

Ted... I don't recall you having a dog in this fight.

What's your position on this other than "Steve's wrong?"

Let's give this a break. I argue with Steve all the time, but lets not get personal. Tolly Wally has plenty to chew on... it's his boat and he'll get his cable installed.

[Tedster]

Oh I get it, it's down on Ted week, same old BOC crap, you guys kill me. So who is going to resign due to stress next?! Palleazzzzzze! Ted