Cutting coaxial cable

[Sea Change]

Fitting an AIS unit and I have a new antenna to install. The connector is done very nicely with heat shrink and solder, so I'm a bit loath to pull it apart. But it won't fit through the cable gland on deck.

If I cut the cable a few inches from the end, could I just rejoin it using something like a choc block? I know it's a bit of a bodge, but I'm limited to what I have onboard. I presume I'd lose some of the shielding effect, and obviously it wouldn't be in any way weatherproof but that won't matter.

 

[Alex_Blackwood]

Fitting an AIS unit and I have a new antenna to install. The connector is done very nicely with heat shrink and solder, so I'm a bit loath to pull it apart. But it won't fit through the cable gland on deck.

If I cut the cable a few inches from the end, could I just rejoin it using something like a choc block? I know it's a bit of a bodge, but I'm limited to what I have onboard. I presume I'd lose some of the shielding effect, and obviously it wouldn't be in any way weatherproof but that won't matter.

Can't you do something with the AIS unit end rather than the "On deck" antenna end of the cable. Without seeing the connectors difficult to say.

 

[Refueler]

Of course it would work - but reduced ... and liable to pick up - radiate interference.

Its always better to remove plug ... run cable through - then replace plug.... its actually not that bad a job ...

OK ... there is another way - shown to me by an Electrical Engineer ... which works on the principal of the cables construction.
I did it on my 25ft boat and it survived many years ... SWR meter showed it was fine ... VHF diagnostic had no issue with it etc.

Cut cable. Feed cable through ...

Now remove outer insulation revealing the shielding meshed foil or wire. push this back so the inner hard insulated core is clear. Remove a short setcion of the hard insulation exposing the inner wire. Do this for both cable ends.
Now solder the two inner wires together - basically one laying alongside the other. Try to keep solder from blobbing ... it needs to be smooth and along the joint. You can take a file to it if not.
Now take insulation tape and wrap the inner wire joint until its level with the hard insulation.
Now pull the meshed foil or wire back over the joint and make sure the two mesh together.
Wrap outer with insulating tape to recreate the cable ....

What you are basically doing is recreating the physical form of the cable ... the distance between inner core wire and outer mesh shield is important to create.

Best is Self Amalgamating tape.

 

[Sea Change]

Can't you do something with the AIS unit end rather than the "On deck" antenna end of the cable. Without seeing the connectors difficult to say.

It's at the AIS (indoor) end that I'd make the join.

 

[Sea Change]

Of course it would work - but reduced ... and liable to pick up - radiate interference.

I guessed it might. Does it matter that this is only for AIS, not VHF?

Its always better to remove plug ... run cable through - then replace plug.... its actually not that bad a job ...

I know what you mean, but it's just that this is a brand new fitting and I'm certain by the time I'd taken it apart and remade it, it would be nowhere near as good...

OK ... there is another way - shown to me by an Electrical Engineer ... which works on the principal of the cables construction.
I did it on my 25ft boat and it survived many years ... SWR meter showed it was fine ... VHF diagnostic had no issue with it etc.

Cut cable. Feed cable through ...

Now remove outer insulation revealing the shielding meshed foil or wire. push this back so the inner hard insulated core is clear. Remove a short setcion of the hard insulation exposing the inner wire. Do this for both cable ends.
Now solder the two inner wires together - basically one laying alongside the other. Try to keep solder from blobbing ... it needs to be smooth and along the joint. You can take a file to it if not.
Now take insulation tape and wrap the inner wire joint until its level with the hard insulation.
Now pull the meshed foil or wire back over the joint and make sure the two mesh together.
Wrap outer with insulating tape to recreate the cable ....

What you are basically doing is recreating the physical form of the cable ... the distance between inner core wire and outer mesh shield is important to create.

Best is Self Amalgamating tape.

Interesting. I wonder if I could build it up with heat shrink sleeves? With a bit of tape over the top to get to the right diameter.

 

[Martin_J]

Or perhaps buy a plug that you can install at the end of the co-ax that will plug directly into the AIS unit.

That would save having a potentially lossy/reflective additional connection just a short distance along the wire.

 

[Refueler]

I guessed it might. Does it matter that this is only for AIS, not VHF?

[/QUOTE]
IMHO - the lower power of AIS would be less able to cope with the choc block

I know what you mean, but it's just that this is a brand new fitting and I'm certain by the time I'd taken it apart and remade it, it would be nowhere near as good...

[/QUOTE]
Its often better to just fit a new plug ... you can get ones that don't need solder ... they have little screw pressing on inner core and outer mesh is pressed into outer sleeve.

Interesting. I wonder if I could build it up with heat shrink sleeves? With a bit of tape over the top to get to the right diameter.

Of course - the trick is to keep the diameters right .. and the shield intact.

 

[Refueler]

Or perhaps buy a plug that you can install at the end of the co-ax that will plug directly into the AIS unit.

That would save having a potentially lossy/reflective additional connection just a short distance along the wire.

?? As I understand it - its the antenna plug that he cannot pass through deck gland - so he can plug it into the AIS.

 

[Alex_Blackwood]

I guessed it might. Does it matter that this is only for AIS, not VHF?



I know what you mean, but it's just that this is a brand new fitting and I'm certain by the time I'd taken it apart and remade it, it would be nowhere near as good...



Interesting. I wonder if I could build it up with heat shrink sleeves? With a bit of tape over the top to get to the right diameter.

I wouldn't worry too much about the dia. as long as you can insulate the inner from the sheath and cover the sheath for protection.
I would suggest anything such as refueller suggests is somewhat better than choc blocks
I would start by looking to see how difficult it is tom actually remove and replace the original connector.

 

[Refueler]

I wouldn't worry too much about the dia. as long as you can insulate the inner from the sheath and cover the sheath for protection.

The distance between inner core and the shield is actually the factor that decides the spec of the cable .....

How Does Coax Work? A Comprehensive Guide to Understanding Coaxial Cables - BlinksAndButtons

 

[Plum]

Fitting an AIS unit and I have a new antenna to install. The connector is done very nicely with heat shrink and solder, so I'm a bit loath to pull it apart. But it won't fit through the cable gland on deck.

If I cut the cable a few inches from the end, could I just rejoin it using something like a choc block? I know it's a bit of a bodge, but I'm limited to what I have onboard. I presume I'd lose some of the shielding effect, and obviously it wouldn't be in any way weatherproof but that won't matter.

Using a chock block is a bodge but for AIS receive only it does work. I did it as a temporary measure and as I got very acceptable receive range I left it in place.

 

[PaulRainbow]

Of course it would work - but reduced ... and liable to pick up - radiate interference.

Its always better to remove plug ... run cable through - then replace plug.... its actually not that bad a job ...

OK ... there is another way - shown to me by an Electrical Engineer ... which works on the principal of the cables construction.
I did it on my 25ft boat and it survived many years ... SWR meter showed it was fine ... VHF diagnostic had no issue with it etc.

Cut cable. Feed cable through ...

Now remove outer insulation revealing the shielding meshed foil or wire. push this back so the inner hard insulated core is clear. Remove a short setcion of the hard insulation exposing the inner wire. Do this for both cable ends.
Now solder the two inner wires together - basically one laying alongside the other. Try to keep solder from blobbing ... it needs to be smooth and along the joint. You can take a file to it if not.
Now take insulation tape and wrap the inner wire joint until its level with the hard insulation.
Now pull the meshed foil or wire back over the joint and make sure the two mesh together.
Wrap outer with insulating tape to recreate the cable ....

What you are basically doing is recreating the physical form of the cable ... the distance between inner core wire and outer mesh shield is important to create.

Best is Self Amalgamating tape.

I've done this years ago when having to splice the coax in old analogue radar cables, always worked fine.

 

[Martin_J]

?? As I understand it - its the antenna plug that he cannot pass through deck gland - so he can plug it into the AIS.

Indeed.

My suggestion was to cut off the antenna plug, feed the wire down through the gland, then install a new plug onto the cut cable end..

The cable was going to be cut close to the end anyway, so installing a fresh plug would, in my view, lead to the most reliable solution.

 

[Alicatt]

When I opened the instrument cluster on our boat the GPS mushroom was connected to the chart plotter via choc-block connector and the VHF radio in the saloon was also connected by a choc-block. Was an easy fix replacing the cables and putting on proper connectors.
I have stroked the installer off from my list of approved companies

As this was all done before the boat came into my possession, the VHF and chart plotter both worked, but the difference in reception having proper plugs on the cables was noticeable. Before, the AIS reception was a bit hit and miss, range was about 1km in open water, after changing the cable and plugs I am getting ships positions from 37km away and that is through quite dense wooded country on the canals.

 

[jwilson]

Two solderless 50 ohm plugs and a joining connector- what I have under deck as a masthead VHF antenna connector. Both VHF and AIS work well. All came from CPC Farnell.

 

[Sea Change]

Two solderless 50 ohm plugs and a joining connector- what I have under deck as a masthead VHF antenna connector. Both VHF and AIS work well. All came from CPC Farnell.

In sure that's a great solution, but I want to compete this job with what I already have to hand.
(Nearest inhabited land is Necker Island and I doubt Richard would be in a position to sell me a couple of connectors!)

I've cut the end off about a foot back from the plug, I'll try Refueler's method.

 

[john_morris_uk]

In sure that's a great solution, but I want to compete this job with what I already have to hand.
(Nearest inhabited land is Necker Island and I doubt Richard would be in a position to sell me a couple of connectors!)

I've cut the end off about a foot back from the plug, I'll try Refueler's method.

Just sail a few miles in my direction and I’ll sort if for you! Not for nothing was I at the Royal Radar Establishment for a couple of years after leaving school. I might even have some connectors on board.

 

[zoidberg]

Just sail a few miles in my direction and I’ll sort if for you! Not for nothing was I at the Royal Radar Establishment for a couple of years after leaving school. I might even have some connectors on board.

Sounds like an excuse for a party!

RRE Malvern, eh? I, too, spent some time there during the 70s, but focussed on Real Time IR.

We may have crossed paths, but probably couldn't communicate. The acronymphs were different...!

 

[john_morris_uk]

Sounds like an excuse for a party!

RRE Malvern, eh? I, too, spent some time there during the 70s, but focussed on Real Time IR.

We may have crossed paths, but probably couldn't communicate. The acronymphs were different...!

We might indeed have crossed paths. I worked for Michael Dunsmore for a year (developing systems for measuring the noise side bands of microwave sources.) and then for another section developing automatic recognition of targets through chaff. Late 70’s.

 

[Alicatt]

Arrr, it was Decca Radar that I served my time with, built my first computer with them on a training course when we were learning about digital logic and how it applied to target tracking in an anti collision radar set.

1973/4 in Croydon at Decca HQ.