Co-ax cable

[Jules]

Does any one know a bullet-proof way to join co-ax? I have a Garmin 128 whose supplied lead is 8 feet too short. Worked fine for 2 years, then took ages to acquire a fix. Fitted new aerial (£80!!!!!), worked ok, then back to old tricks.
Garmin checked it and the aerial, gave me a new one FOC!!!!, but now refusing to acquire again. Must be the joint.
HELP!

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[nickjaxe]

I dont fully understand you say 8ft short how were you getting it to work, are you splicing the cable.

Nick.

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[Jules]

No, it was joined with a radio (VHF) co-ax cable joint

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[nickjaxe]

Where you able to try it before you put the new length of cable in.

Nick.

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[Jules]

It was tested by garmin as the set and standard mushroom aerial and 30' lead. The problem appears to be when I connect the lead into the extension to get it to reach the nav. station

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[Steve Clayton]

Could it be an impedance mismatch between the 2 co-ax cables??? The co-ax sheath should have the impedance marked - could be 50 or 75 ohms. If there is a difference between the two then this could be the problem.

Well made BNC connectors between the two lengths should resolve any sort of connection problem that might exist.

Hope you sort it OK.

Steve

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[broadcaster]

Hi,

I would agree, check the impedance of the cable and make sure you match the connectors for it. A good quality BNC and joining piece would be a good solution, but again make sure they are the right impedance and correct size for the cable.

Andy


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[nickjaxe]

Thats what I was thinking, the signal strength is so very very tiny from 11.000mls away, that any mismatch or poor conection will loose the signal.
Nick.

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[VicMallows]

The cable on my Garmin 128 is RG58A/U which is fairly basic computer-grade 50ohm coax.

I'd be very surprised if an impedance mismatch was causing you the problem. To the best of my knowledge (please correct me if anyone knows otherwise) the signal from the active antenna is at quite a low frequency. Certainly all last season I used a short length of cable from the antenna connected to the set via a decrepid piece of old 93ohm coax that happened to be conveniently installed. A basic twisted connection each time I used the boat with no attempt at a coax connection. HERESEY, I know!! ..... but no discernable degradation in signal.

And better than tripping over the direct cable I'd put up with the year before.

Vic

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[Jules]

Thanks all, i'll go and fiddle with it

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