GPS antena

nickjaxe · 01 March 2004, 10:49

Hi all working on our club RIB all w/e and we are having probs with the gps, its a MLR unit powers up ok but cannot get any satellites at all on it, the antenna is mounted on the rear a frame which itself folds over, we have noticed that the antenna cable has been trapped by the folding a frame and badly squashed but cannot tell if it broken inside outer plastic is not broken just very squashed, anybody know of any easy way to check this out I do have a good mutimeter, and if it does turn out to have an internal break can we just splice or do we need a new antenna, hope not we had to buy one for a garmin some years back and it was not far of the price of the complete unit.

Regards nick.

jwalker · 01 March 2004, 11:45

Its unlikely to be broken inside. However, put your meter across the cable connector to see whether it's a full short or open circuit. I don't know anything about this particuar antenna and it is possible it could show a short and not be faulty.
I've just checked a Garmin one for you and it gives about 2.5k across the connector. That's just a guide though.
I've spliced GPS co-ax without problem.

nickjaxe · 01 March 2004, 12:05

Thanks very much JW thats a help, I will try with the meter, tell me why did you have to do a splice on yours and was it a case of just joining the wires or maybe soldering them, how did you waterproof it after, sorry for all the questions.

Nick.

jwalker · 01 March 2004, 12:29

On one occasion I needed a longer cable. The other occasion, last week, I fitted a system to a car and wanted to make the hole in the body work as small as possible.
It's 50ohm co-ax. I fold back the screen on both ends for about 15mm. Slip some shrink over the cable outer. Shorten the inner and tin just about 1mm on each centre conductor leaving a wee blob on one of them. Next, solder the tips together and quickly push them together while they are still hot. They will push up inside the core until the cores butt and become virtually continuous. The wee blob of solder retains the heat for long enough for you to do this, (if you're quick

).
Ensure it's well done, bring back the screen from one end and smooth it. Bring back the screen from the other end to form an overlap. Give it a wee touch of solder just to ensure a sound conductor, then slide the shrink over the top and shrink it.
If it is going to be subject to the weather, I would also make a sleeve from silicon tube because it makes a completely watertight seal.

nickjaxe · 01 March 2004, 15:27

Thanks for that JW sounds a very good method I wll let you know how we go on, did it work just as good after the cables were joined.

Nick.

jwalker · 01 March 2004, 16:26

Yep. Signal strengths were exactly the same.