Cutting GPS cable....

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All_at_Sea

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I have to re-site two GPS antenna which run through a deck gland and then into the boat behind everything! Instead of having to re-route the wires can i simply cut the cables below deck and use a connector to put it all back together? If so what connector do l use?
 
The best connector to use for your GPS antenna cables are BNC (Bayoneted 'N' Connector).

As you are dealing with two cables, you will need double of everything.

See the Maplin link I am sending you and look for:

BNC Female Coupler (2 off) - Part number YW02C @ £3.29

http://www.maplin.co.uk/module.aspx?moduleno=1578


BNC Twist-on (4 off) - Part number JK21X @ £1.79

http://www.maplin.co.uk/module.aspx?moduleno=1563


A good idea would be to use self-vulcanising tape to finish off the two joints on completion @ £7.29.

http://www.maplin.co.uk/Module.aspx?ModuleNo=4099


You MUST use the 50 Ohm ones and not the 75 Ohm ones and I am suggesting 'Twist-on' for two reasons.

Firstly, the GPS is a receive only unit and no RF power will pass up to the antenna as it would if you were using the cable for your ships wireless transmitter, and secondly . . .

They are easier to fit by someone with limited knowledge or skills (soldering a small co-axial cable is not easy if you have never fitted a BNC connector before).

Your local Maplin stores in Hampshire can be found on this link:

http://www.maplin.co.uk/StoreLocator.aspx?cmd=searchregion&regionid=9

I Hope this info is of help? /forums/images/graemlins/smile.gif


http://www.maplin.co.uk/Search.aspx?criteria=bnc&source=15
 
It depends upon the age of the cable. If it's in good nick you may be be able to solder but far more likely it won't be. You can usually get good enough results just using a connector block.
 
I know that this reply will lower my already low reputation, but we have just fitted a "Goalpost" to carry a solar panel, a wind generator and the GPS aerial. I had to cut the plug off to re-run the aerial cable, and, pro tem, in the absence of a replacement BNC plug (the old one was moulded on, and not reusable) I divided the inner and outer of the coax and connected them with a two way terminal block, the sort one would use for 12V connections. Works fine! But I am going to buy the right BNC plug when I can, honest!
 
First class. You cannot always get the right connector when you need it and it looks like you have completed an effective repair which works.

As I said above, the GPS antenna cable (and AIS units) do not need to carry any RF output power and any temporary joints/junctions are not problematical.

The only problem I could foresee with a 'chocolate block' connector is with the steel screw mating on a copper wire. These dissimilar metals are not good bed-fellows. Long term you are going to get a cathodic action and corrosion will slowly degrade the junction causing loss of signal. This won't be noticeable at first but will slowly degrade if left.

If you look at a copper lead which has been in contact with another type of metal (steel), for any length of time, you will notice the copper will have turned turned black. This effect is speeded up with salt spray or sea water ingress.

Any way well done on your 'repair'.

Best to change it at your earliest convenience, I appreciate this is not easy when you are cruising. /forums/images/graemlins/cool.gif /forums/images/graemlins/cool.gif
 
Many GPS "antennas" are not really "antennas" at all, but are complete GPS receivers. So the cable is not handling RF frequencies at all, but is passing data signals down to the display and passing control signals up to the receiver.
If so, you will be dealing with three or four strand cable, (similar to telephone cable) rather than co-ax.
In which case you can use any form of reliable connection that you would consider acceptable for low voltage wiring.

Fair winds
Tim
 
Check what the receiver's handbook says. My old Philips is quite specific about not shortening the cable.

GPS works by measuring the time it takes for the signal to travel to the receiver from each satellite, which includes the time it takes to go down the cable from the antenna. If you have 10m of cable (say) then the receiver expects 10m worth of delay from it. That may not be important, if you don't want accuracies of that order.

Currently the GPS specification is for 13m average, 33m worst case. It actually does better.
 
Lensman is being very polite!! I wish I had the same restraint!


chock-block is ok for an emergency bodge, but for anything semi permanent it is really dreadful. For something mission critical, like a GPS coax I would not dream of using it. Apart from anything else, just one 'hair' from the screen making contact with the centre conductor will completely kill reception.

A bodge with a soldering iron and self amalgamating tape is far preferable and just as easy.

Of course there is no problem with shortening the wire per se, provided it is done properly.
 
[ QUOTE ]
Check what the receiver's handbook says. My old Philips is quite specific about not shortening the cable.

GPS works by measuring the time it takes for the signal to travel to the receiver from each satellite, which includes the time it takes to go down the cable from the antenna. If you have 10m of cable (say) then the receiver expects 10m worth of delay from it. That may not be important, if you don't want accuracies of that order.

Currently the GPS specification is for 13m average, 33m worst case. It actually does better.

[/ QUOTE ]

This may be true of older sets that antena was antena. But most sets now are actually only displays with real GPS engine in the antena block itself. The cable then only feeds data to the display.
Also I can be confident that even my old Magellan hand-held can have it's antena disconnected, a patch BNC cable inserted between GPS handheld and the antena - here the engine is in the handheld part ....
The cable timing is usually referred to with Echo-sounders.... where cable length is part of calculation.
 
[ QUOTE ]
Check what the receiver's handbook says. My old Philips is quite specific about not shortening the cable.

GPS works by measuring the time it takes for the signal to travel to the receiver from each satellite, which includes the time it takes to go down the cable from the antenna. If you have 10m of cable (say) then the receiver expects 10m worth of delay from it. That may not be important, if you don't want accuracies of that order.


[/ QUOTE ]With respect this is a load of tosh.

The 'time delays' from the signal entering the antenna to the time it gets processed don't produce errors as the time delay is effectively the same for all the signals. The way that the GPS receiver actually decodes the signal and does some very clever maths to sort out where it is relative to the satellites does not rely on the velocity factor and length of the cable to the antenna.

This is all assuming that the antenna is actually an antenna and not the GPS engine itself. If the antenna is actually the GPS engine, it doesn't matter about the length of cable to it either.
 
Rather than 2 sockets and an adapter, a socket on one end and a plug on the other would make for less connections.

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