BNC Connectors for Transducer Wiring

[Ron Hill]

Interesting information  --  I used those Radio Shack BNC connectors to wire in an A/B switch so I could display Loran or GPS data to a cockpit display.

I also soldered the coax wires and used those "poor quality" RS connectors. 
That system preformed flawlessly for only 20+ years, until USCG stopped funding LORAN !!!!!

A thought

[Stu Jackson]

I found a BNC to BNC connector:  https://www.youtube.com/watch?v=aoRwPPrY9z8  See minute 3:45.

There are also twist-on BNC connectors so I don't have to purchase a crimper.

Looks like it's worth getting a stripper instead of trying to strip the insulation back with a box cutter - that RG59 is too small for even my tired old eyes to see without a magnifying glass!!!

PROGRESS UPDATE:

Bought what Amphenol calls "Super Twist" BNC connectors and a BNC "Inline Splice" fitting, so the old female connector on the transducer wire will be replaced by a male with the inline splice fitting between them.

The stripper was a wise investment.  DMI nicely got back to me, advised 50 ohm, RG58.

I started on the long 30 foot wire that goes back to the cockpit.  Foot by foot, I found the braided wire to be completely compromised --- the water had wicked up through the cable under the insulation, back to at least five feet aft of the mast.

Surprising that the knotmeter worked as long as it had.

I returned to the electronics store (Al Lasher's Electronics in Berkeley - a truly great place out of the 1950's!!!) and the helpful owner suggested that I purchase a pre-made BNC to BNC 12 foot cable, saving me both effort and $ for two more Super Twists, and another inline splice.

Next step is to work my way back to un-compromised braid on the long wire going aft and then do the same for the wire forward to the transducer.  If I need more, I know I can get either 6 or 12 foot BNC to BNC pre-made extensions.

Great store, great help (nice to have someone who knows their business to suggest something you didn't even ask for or know existed that saves both time & $$$-how quaint! ).   Also many thanks to a few skippers on co.com who helped me understand the possibilities and materials available.

More to follow.  Glad I don't have to splice this stuff, it's TINY.  

Pictures at eleven!  

[Stu Jackson]

Complete success.   Knotmeter works.  Tech Notes written for next issue of Mainsheet.

[KWKloeber]

Complete success.   Knotmeter works.  Tech Notes written for next issue of Mainsheet.

do you have a pic of a finished terminal?
k

[Stu Jackson]

Not a finished one, but here are the parts:

[KWKloeber]

cool thanks Stu, looks easy enough to use 

And these are screw on- not crimp, correct? 
Hopefully they won't end up in the bilge again 

Are you HST-ing them, for a moisture guard?

k

[Stu Jackson]

The picture showed the new screw on (called Twist On by Amphenol) with a BNC to BNC connector.  Old transducer wire >>> new twist on >>> butt connector >>> new premade BNC to BNC patch cord >>>  butt connector >>> new twist on >>> old long wire to cockpit.

Yes, the last one's in the bilge, no stopping that geometry, but it is now high up just under the floorboard across from the nav station, instead of where it was in front of the mast and down in the water (yuck!).  The forward one is way up in the V berth since I got a looong patch cord.

I have started to shield the new connectors.  Started on the bilge one with a thin roll of butyl tape pushed into the lip between the base of the twist on connector and the outer insulation, then wrapped with tape.

Then I'm planning on doing this, thanks to Forest from Mandeville, LA on co.com.  I will do it step by step to make sure everything continues to work. 

I think Ron Hill's advice to always do one thing at a time so you KNOW where the problem comes from is EXCELLENT.

You can definitely use the butyl tape Maine Sail sells. just wrap it in electrical tape. In fact, that's how RF connectors are typically wrapped for weatherproofing. The butyl, especially the black kind used on connectors, will stick to the connector and can be messy. What many do is first wrap the completed and connected junction in electrical tape, wrap that in butyl, then wrap the butyl in more electrical tape. when done, the cable will look like a snake that has just eaten something. I have seen this hold up in sun/rain for many years. There are other products that would work well and not as messy. I have been using self fusing silicone tape made by 3M and like the properties of it. It doesn't leave any sticky residue and seems to hold up well exposed. I still wrap it with electrical tape on my connections just to protect the soft silicone material.

The jury is still out on whether I'll need to do the one in the V berth, since it'll be out of any water and I can see how it's holding up.  I may just do the butyl tape at the joint of the twist on and wrap that in tape.  We'll see.  After all, the simple BNC connector that was in bilge water for the past 30 years did it for, well, 30 years, right? 

Details in an upcoming Mainsheet Tech Note, and the Tech Notes Online. 

TNO is here:  http://www.c34.org/mainsheet/html/2015/Knotmeter%20Cable.htm