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Old 24 April 2016, 18:40   #1
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VHF interference

Hi all,

Fitted a new Cobra VHF to the rib into the former VHF switch panel and antenae.

On first test from the boatyard with engine off, the Coastguard and I were crystal clear. Off from the pier with the engine ticking over, noisy and crackly!

Any quick check tests to find the cause?

Any cures?

Could it just be emf interference from the antenae cable being too close to other cables or spare cable being coiled together (as can happen with TV cable and plug cables)?

Cheers Stevie
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Old 25 April 2016, 04:07   #2
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Did you fit new coaxial cable and solder in the ends of the PL259 connectors? There's no real reason to have the cable coiled. Allow some excess if you ever have to re-solder the ends. Personally I'd cut to size. Try that and see if there's any improvement.
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Old 25 April 2016, 11:37   #3
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Often, it's the VHF cable laying next to the wiring harness that drives your tachometer. Might be able to tell by seeing if the noise varies pitch when revving the motor. Fish finders may cause interference, but it's usually a clicking noise rather than something more like static. Pretty much anything that has a signal with an AC component can cause interference.

As I recall (and some research is probably in order, as my recollection may be faulty), my Digital Antenna instructions had a warning that excess cable should not be neatly coiled. Not sure what they wanted you to do with it though.

Luck;

jky
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Old 25 April 2016, 12:34   #4
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Quote:
Originally Posted by jyasaki View Post
Not sure what they wanted you to do with it though.
Hmmm. Whoever wired my last boat could help you there - a totally random fall of cables - tacked down...
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Old 25 April 2016, 12:58   #5
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Definitely cut coax to required length. There are all sorts of reasons to avoid coils. Try and route the coax away from other electrical cables.
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Old 25 April 2016, 13:51   #6
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I've cut a metre off the coax and reatted the end.

I'll check the wiring loom to see where the ariel cable lies and make sure the power lines under the console are also clear of the ariel.

Hopefully that clear up the crackling.

Do you reccomend I solder the end of the coax tip? Wasn't in the old set up.

Cheers S
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Old 25 April 2016, 14:49   #7
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Do you reccomend I solder the end of the coax tip? Wasn't in the old set up.
Definitely. Think about the vibration on the average RIB. Any stresses on coaxial cable ends could be a possible fault in the making. Takes minutes to do and gives you peace of mind that the connection ends on your cable are nice and secure.

I do the same for battery cables, positive feed to the starter motor, etc.
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Old 28 April 2016, 03:30   #8
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Yes, solder tip but be careful to avoid solder blobbing on the outside of the centre contact or you will struggle to get the connector on.
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Old 28 April 2016, 04:24   #9
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Hi

For what it's worth I was told to stay away from Cobra,not a very good brand.
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Old 28 April 2016, 04:49   #10
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Hi

For what it's worth I was told to stay away from Cobra,not a very good brand.
Why that then, I remember in the 80's when Cobra was one of the main rigs to have on the CB scene.

Been around a long time,,if they were no good, don't think they would have survived
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