Raymarine Wires - shortening

[nofd843]

I have a sailboat that is running a Raymarine Speed (ST40), Wind (ST60 I think), Depth (ST40) and Autopilot (it is a 2006, not sure of the model, wheel drivenautopilot) and my question is this, can I trim back the wires that run from the depth sounder, wind and speed sensor and affix new female connectors? I am unaware if there is a specific impedence that is created based on the length or if it just reads pulses or something. When these items were installed the installer rolled the wires up and crammed them all into the pedestal. I am currently out of the country and I am making plans for when I get back, any help in preparing me to clean up this rats nest would be appreciated.

Jeff

 

[flynfol]

I have ST50 instrumentation, and if I recall correctly, I was able to shorten everything but the depth. It seems that the depth is a timed signal from indicator/control to the probe and back. Any change in length may throw off your indication. Coil it up below deck, or in the bilge(what I did). Not positive, but kinda what I remember.

J

 

[alexco38]

Untidy installation

I would fire the "installer rolled the wires up and crammed them all into the pedestal."

You can cut any wire except the depth sounder cable which is impedance matched at the factory. Cut the wire before the plug and solder them back and then put a heat shrink tube over it to make it water tight again.

 

[Rich Stidger]

Although I am a neat freak myself, I wouldn't shorten any of the wires. Neaten them up and tie in coils if possible. But flynfol's advice about the depth cable is correct as far as I know.

The best reason for not cutting is that every splice is an opportunity for a failure and if the cables are coiled and out of sight, what is the harm?

 

[Snotter]

I agree with the advice on not cutting the sounder wires if possible; however, if you damaged the connector at one end and just need to trim an inch or two off a damaged cable I would think that that may be doable as a last resourt before buying a new cable or transducer.

 

[Calif. Ted]

If the wires are rolled and stuffed in the Navpod as is the case with most boats why bother? With any luck you won't ever open it again, lots of expensive boat projects start with fixing something that isn't broke.

 

[Bill Roosa]

Depth sounder cables

While the factory says to not cut/shorten the cable you can. It carries a high frequency signal so noise is a concern. However just changing the "feed line" and not the display or transducer will not change the cables impedance. Just follow good cable connector practice and make sure the grounding "sheath/wire" is sufficient. It is important to keep noise out and signal in. Google "RF connectors" for some tips.
Given how long these cables get left in boats, you might be money ahead to leave them long just in case you (or another owner) wants to move the display heads.
Remember to test burn the coiling of wires before you close up the pedestal as coiling a wire bundle does change its impedance and can cause signal attenuation.

 

[Don12364]

In many sounders the PZT transducer (lead zirconate titanate) plus its cable represents the capacitive part of a tuned circuit to which the transmitter output driver stage is carefully matched. The intention being to resonate this circuit at the natural frequency of the PZT crystal in the transducer - often 47.5KHz. Shortening this cable will reduce the capacitance and thus reduce the power received by the transducer to inject into the water, though it will not affect the frequency of the signals.
To be honest it is not normally very critical so you could re-make the end connection at the plug several times without loosing too much sensitivity and this leads to people believing it does no harm. But it will cost something in a lesser response in deep water and a muddy bottom.
However wanton shortening it just for convenience is tantamount to sabotage.

Last Century, when I worked for Raytheon (not Raymarine), I designed a chart recording fish finder sounder for commercial fishing with a red line bottom lock and this could detect fish only 2 feet off the bottom in half mile deep water. The transducer was a mighty bronze cast shell with 4 off transducer PZTs inside and a 1KW pulse power.
It was a beast.

 

[Chuckbear]

Jeff, You have received a lot of feedback on the depth sounder cable. You can but should not cut and splice the transducer cable. Most of the rest of the wiring is Seatalk cable and those can be cut with no issues. The red and black are power and ground and the yellow data. Any power cables can also be shortened with no problem. As always, attaching new connectors should be done properly. The push on connectors on the back of the displays are not standard sized connectors. The transducer cable might work out OK and it might not. So you have to ask yourself, do you feel lucky today? I am a certified Raymarine tech, by the way. Chuck

 

[Steve Dion]

Chuck:

If a push on connector is NOT standard sized what should one do.

I normally get mine at the local electronics store.

 

[Chuckbear]

They are much narrower. Look and see if some of your connectors on the back of your displays are small and red standard Raymarine connectors. Then you will know the size. I have found them at Radio Shack, or a marine electronics repair shop will have them. Chuck

 

[Ragtime!]

I've also read you should not shorten the cable to the fluxgate heading sensor (autopilot's "compass").

 

[nofd843]

Thanks for all the information. I am hoping when I get home to finish connecting the NMEA and the VHF radio to the system, so while I was in there I was going to try and straighten it up a little. I think I will retract some of the cable and pull the excess from the pedastal and tie it up in the aft compartment. Thanks for all the insight.

Jeff