Cutting a depth transducer cable

[marchem]

I'm looking to add a depth transducer to my Raymarine e7D MFD, to get a graphical depth display. Currently I've got a P19 connected to an ST-60 display, so I only get a numerical depth value.

I'm pretty certain the plug for the new transducer (I'm thinking either a P319 or P79 in-hull) will not fit up the tubing to the Navpod holding the e7D at the helm. Raymarine says to never cut the depth transducer cable. Airmar (who makes the transducers) says it's ok to cut them, if you use their Junction Box No. 33-035. I've also read of people who carefully cut and soldered their depth cables. Seems to me that Raymarine is being overly cautious, and worried about people doing a poor job themselves.

Any thoughts from this group on splicing versus the junction box?

Alternatively I could go with a CPT-S Transducer and a CP100 DownVision Sounder Module, then use RayNet to send the send the graphical display to the e7D, but that's an expensive option, and doesn't come in an in-hull version (no haul out planned for a few years, I hope).

 

[dlochner]

I'm pretty certain the plug for the new transducer (I'm thinking either a P319 or P79 in-hull) will not fit up the tubing to the Navpod holding the e7D at the helm.

Sometimes the issue with snaking wires is the sequence. Run the wire with the biggest plug first, then the next largest, and so on. This may require removing the wires that are current installed and reinstalling them. It seems unlikely that Airmar or RayMarine would use plugs that could not fit inside a standard tube.

Any thoughts from this group on splicing versus the junction box?

If possible avoid cutting or splicing the wire. If you must, carefully follow Airmar's instructions and realize that Raymarine will probably not give you much support if it doesn't work.

 

[jssailem]

Cables can be cut. I used a pair of wire snips.
Stripped the old 80MHz cables and connected it to a Raymarine Itc-5 Instrument Transducer Converter. Gave me the analog data on the SeaTalkNG backbone.

I suspect you can do the same.
You will need to identify and match the wires in the plug (coming from the transducer) to the wires in the MFD. You should be able to cut then reconnect the wires in the cable (i.e. red to red; brown/blue to brown/blue; whatever they are). Only issue is they are likely very small and present a bit of an issue to get and maintain a good connection. They also may be shielded. The shield is often used as the ground in these cables. You will need to provide a solid ground and shield the cable perhaps with a piece of aluminum foil.
We are talking outside the box ideas here.

The Junction box may be a cleaner method.

Oh and what @dlochner said... Raymarine will not like this.

 

[marchem]

Cables can be cut. I used a pair of wire snips.
Stripped the old 80MHz cables and connected it to a Raymarine Itc-5 Instrument Transducer Converter. Gave me the analog data on the SeaTalkNG backbone.

I suspect you can do the same.
You will need to identify and match the wires in the plug (coming from the transducer) to the wires in the MFD. You should be able to cut then reconnect the wires in the cable (i.e. red to red; brown/blue to brown/blue; whatever they are). Only issue is they are likely very small and present a bit of an issue to get and maintain a good connection. They also may be shielded. The shield is often used as the ground in these cables. You will need to provide a solid ground and shield the cable perhaps with a piece of aluminum foil.
We are talking outside the box ideas here.

The Junction box may be a cleaner method.

Oh and what @dlochner said... Raymarine will not like this.

Unfortunately using the iTC-5 only provides the analog data. It won't give me a graphical display on the e7D.
Outside the box is fine with me. . Inside the junction box does seem cleaner and easier. Interesting that it doesn't maintain the shield over the depth wires in the box, although it does maintain the shield itself (makes sense).

 

[dlochner]

A long time ago, I broke the cable on a Standard Horizon depth sounder (Yes, SH used to make a complete suite of electronic gizmos). When I researched replacing and/or splicing the wire I was told that the impedance of the wire was crucial. If the impedance was not correct the DS would either give an erroneous reading or not work at all. In my case it was not work at all. I believe the issue was the DS signal was electronic, but it was an analog signal that degrade if the impedance was incorrect.

If the new transducer is a 0183 or 2000 based transducer this may not be as big an issue as the data will be sent as a bunch of 0s and 1s which should be less suspectible to the kind of degradation that the old DS signals were.

Someone who has a deeper understanding of the electronics may offer a greater insight on the differences between the old and new signals sent by a transducer. At this point the alarm is going off that I've about run aground with my knowledge.

Edit: Proofreading has never been my forte, there have been a couple of edits to address this weakness. Edits corrected incorrect words, thanks to autocorrect.

 

[marchem]

A long time ago, I broke the cable on a Standard Horizon depth sounder (Yes, SH used to make a complete suite of electronic gizmos). When I researched replacing and/or splicing the wire I was told that the impedance of the wire was crucial. If the impedance was not correct the DS would either give an erroneous reading or not work at all. In my case it was not work at all. I believe the issue was the DS signal was electronic, but it was an analog signal that degrade if the impedance was incorrect.

If the new transducer is a 0183 or 2000 based transducer this may not be as big an issue as the data will be sent as a bunch of 0s and 1s which should be less suspectible to the kind of degradation that the old DS signals were.

Someone who has a deeper understanding of the electronics may offer a greater insight on the differences between the old and new signals sent by a transducer. At this point the alarm is going off that I've about run aground with my knowledge.

Edit: Proofreading has never been my forte, there have been a couple of edits to address this weakness. Edits corrected incorrect words, thanks to autocorrect.

I had a Standard Horizons depth and speed instruments on my J-22 back in the 80s.

The transducers I'm looking at for the e7D are analog, but my understanding of newer transducers is that the impedance is not a critical factor these days. Good shielding is, however, and I think that's a place a lot of DIY folks mess up.

 

[dlochner]

The e7D has N2k connectivity. Why not use a transducer like the Airmar P79s. It has 0183 and N2K and can be mounted inside the hull? http://airmar.com/productdescription.html?id=108

Of course that will start you down the road of an N2K system, no telling where that leads to.

 

[marchem]

The e7D has N2k connectivity. Why not use a transducer like the Airmar P79s. It has 0183 and N2K and can be mounted inside the hull? http://airmar.com/productdescription.html?id=108

Of course that will start you down the road of an N2K system, no telling where that leads to.

Actually I'm already converting the ST60 wind, speed, and depth signals to N2K so the e7D can use them. My understanding is that the e7D won't provide a graphical display with an N2K depth sensor (that's also why the iTC-5 won't work for me).

The CP100/CPT-S combo would work; it connects to the e7D with RayNet (ethernet) and is able to do graphics, but costs a lot more and doesn't have an in-hull transducer.

 

[jssailem]

no telling where that leads to.

Fortunately not to Financial ruin... But one bitten there is a contagion.

 

[jssailem]

Rob, What I understand from the systems is that the CP100 Chirp transducers operated differently They send out a wide signal and then with the long received are able to get back more of the reflected signals which the new software converts to a kind of 3D image. Generating the "Down Vision" interpretation of the reflected signals. A inside the hull transducer is not able to receive the complex signal. It is attenuated by the hull.

 

[dlochner]

Actually I'm already converting the ST60 wind, speed, and depth signals to N2K so the e7D can use them. My understanding is that the e7D won't provide a graphical display with an N2K depth sensor (that's also why the iTC-5 won't work for me).

I'm not that familiar with the Raymarine product line as I'm a B&G guy. However, the B&G Triton2 system does have a graphical depth display and after a few short weeks (yeah, I went down the N2K rabbit hole and didn't end up in financial ruin) I think it is a bit over hyped.

The linear visual display shows what is happening in real and past time. So long as the boat is traveling in a straight line the information is helpful. I thought it would be most helpful when anchoring, so I would not anchor on the edge of a drop off, but I found it confusing and not easy to interpret. The issue is that it records the depth directly under the transducer and does not correct for the course travelled. The display may show increased (or decreased depth) as a result of a change of course and not a change in depth.

This is very different from the CHIRP Sonars that @jssailem mentions. The CHIRP sonars are more like radar in that they display forward, back and side scans of the bottom. (As an aside, the theory behind the CHIRP sonars and the Simrad/B&G radars are the same.) This would be much more useful and more easily interpreted than a 2 dimensional display as it would paint a picture of the bottom around the boat and not just under the boat's transducer.

The linear analog display of the bottom contours is one of those great marketing ideas that sounds good until you actually use it. If you have it as part of the system you are installing, OK check it out. If you are installing a system to get this feature, there are better places to spend your blood, sweat, time and treasure.

 

[Blitz]

Actually I'm already converting the ST60 wind, speed, and depth signals to N2K so the e7D can use them. My understanding is that the e7D won't provide a graphical display with an N2K depth sensor (that's also why the iTC-5 won't work for me).

I use the Raymarine E22158 SeaTalk one to SeaTalkng converter for converting the transducer info for my display and e7. I have an e7, ST60 Wind, i70 display, smartpilot x5 wheel autopilot with display, RAYM DST800 Depth/Speed/Temp transducer and an AIS 650 all talking on the Raymarine network without an iTC-5. (avoiding a N2K network)

 

[marchem]

I use the Raymarine E22158 SeaTalk one to SeaTalkng converter for converting the transducer info for my display and e7. I have an e7, ST60 Wind, i70 display, smartpilot x5 wheel autopilot with display, RAYM DST800 Depth/Speed/Temp transducer and an AIS 650 all talking on the Raymarine network without an iTC-5. (avoiding a N2K network)

I'm guessing that the E22158 is converting only the ST60 wind data from ST1 to STng. The DST800 outputs STng directly to the network (your STng Raymarine network is actually N2K, so you didn't avoid it). Do you get more than a numerical depth value displayed on the e7? Anything graphical?

 

[marchem]

I'm not that familiar with the Raymarine product line as I'm a B&G guy. However, the B&G Triton2 system does have a graphical depth display and after a few short weeks (yeah, I went down the N2K rabbit hole and didn't end up in financial ruin) I think it is a bit over hyped.

The linear visual display shows what is happening in real and past time. So long as the boat is traveling in a straight line the information is helpful. I thought it would be most helpful when anchoring, so I would not anchor on the edge of a drop off, but I found it confusing and not easy to interpret. The issue is that it records the depth directly under the transducer and does not correct for the course travelled. The display may show increased (or decreased depth) as a result of a change of course and not a change in depth.

This is very different from the CHIRP Sonars that @jssailem mentions. The CHIRP sonars are more like radar in that they display forward, back and side scans of the bottom. (As an aside, the theory behind the CHIRP sonars and the Simrad/B&G radars are the same.) This would be much more useful and more easily interpreted than a 2 dimensional display as it would paint a picture of the bottom around the boat and not just under the boat's transducer.

The linear analog display of the bottom contours is one of those great marketing ideas that sounds good until you actually use it. If you have it as part of the system you are installing, OK check it out. If you are installing a system to get this feature, there are better places to spend your blood, sweat, time and treasure.

I agree that the CHIRP provides a lot more information, but with significant costs and complexity. I'm remembering the linear/graphical displays from a Garmin fishfinder I had. I'm pretty sure that a P319/P79 transducer connected directly to the e7D will give me the same thing

I don't understand how "the display may show increased (or decreased) depth as a result of course and not a change in depth"? All it does is measure depth.

 

[dlochner]

I don't understand how "the display may show increased (or decreased) depth as a result of course and not a change in depth"? All it does is measure depth.

On the B&G Triton2 the display shows a bar graph of the depth that scrolls off the display over a set time period. It is accurate for the course the boat sails, however, if the course is not a straight line, it can give the illusion that the bottom contour is changing while the course is remaining steady, when the reality is the depth has changed because the course has changed. The display may show a increase in depth from 5 minutes ago to now, but it doesn't show the change in depth relative to the course. The depth may have changed because the boat changed course 5 minutes ago or the depth may have changed because the bottom contour changed while the boat's heading remained steady.

 

[marchem]

On the B&G Triton2 the display shows a bar graph of the depth that scrolls off the display over a set time period. It is accurate for the course the boat sails, however, if the course is not a straight line, it can give the illusion that the bottom contour is changing while the course is remaining steady, when the reality is the depth has changed because the course has changed. The display may show a increase in depth from 5 minutes ago to now, but it doesn't show the change in depth relative to the course. The depth may have changed because the boat changed course 5 minutes ago or the depth may have changed because the bottom contour changed while the boat's heading remained steady.

Got it. That's the same as the B&G on the boat I race on. I agree that it's not that useful, except for those times when we want to see how close we came to hitting the sand bar at our harbor entrance!
I'm looking for something more like this:

 

[dlochner]

Got it. That's the same as the B&G on the boat I race on. I agree that it's not that useful, except for those times when we want to see how close we came to hitting the sand bar at our harbor entrance!
I'm looking for something more like this:

Those images show both the bottom contour, fish, and weeds. The transducer must be more sensitive than the one on my boat to distinguish between the different bottom types. Thick weeds and soft muck play havoc with my DS. At the dock the weeds are no so thick there is no bottom. Same in parts of the bay, it will go from 30 feet to infinity in the matter of a few yards. I know the bay has a bottom, it is just so soft that the signal doesn't bounce back.

 

[marchem]

Those images show both the bottom contour, fish, and weeds. The transducer must be more sensitive than the one on my boat to distinguish between the different bottom types. Thick weeds and soft muck play havoc with my DS. At the dock the weeds are no so thick there is no bottom. Same in parts of the bay, it will go from 30 feet to infinity in the matter of a few yards. I know the bay has a bottom, it is just so soft that the signal doesn't bounce back.

It may be the sounder electronics, frequency, power, resolution, etc. I think the track on the B&G is just a time lapse display of a numeric depth value, which is probably the strongest return. For (racing) sailboats that's usually all they want or need. The graphical display shows multiple returns from a single pulse in pseudo color.

 

[jssailem]

It may be the sounder electronics, frequency, power, resolution,

Yes all of that.
I think of it as dropping a 2lb rock into a puddle. Then watching the ripples that are created. The pretty color graphics comes from the strength of the returning ripples. The track happens when you drop a series of rocks at a measured time (distance) apart. The sensitivity of the receiver and the associated electronics and computer analysis data (rudimentary data stored frequencies) give you the display elements. A fish has a given strength and frequency response. That it is up in the water and not near the harder bottom causes the display to present a particular image. This is happening at a rapid rate. You may be able to hear the "pings" or thuds being generated by the transducer. The short window of silence following the Thud is for listening. The listening is as important or even more so than the ping.
"A Single Ping Vasily, One ping only"

 

[marchem]

Yes all of that.
I think of it as dropping a 2lb rock into a puddle. Then watching the ripples that are created. The pretty color graphics comes from the strength of the returning ripples. The track happens when you drop a series of rocks at a measured time (distance) apart. The sensitivity of the receiver and the associated electronics and computer analysis data (rudimentary data stored frequencies) give you the display elements. A fish has a given strength and frequency response. That it is up in the water and not near the harder bottom causes the display to present a particular image. This is happening at a rapid rate. You may be able to hear the "pings" or thuds being generated by the transducer. The short window of silence following the Thud is for listening. The listening is as important or even more so than the ping.
"A Single Ping Vasily, One ping only"

Old timers may remember early fishfinders with a neon lamp spinning in a circle. The brightest flash was the bottom; weaker flashes were fish...