VHF interference

Stevie J · 24 April 2016, 23:40

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

spartacus · 25 April 2016, 09:07

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.

jyasaki · 25 April 2016, 16:37

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

willk · 25 April 2016, 17:34

Quote:

Originally Posted by jyasaki

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...

Firefly · 25 April 2016, 17:58

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.

Stevie J · 25 April 2016, 18:51

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

spartacus · 25 April 2016, 19:49

Quote:

Originally Posted by Stevie J

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.

Firefly · 28 April 2016, 08:30

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.

dave3235 · 28 April 2016, 09:24

Hi

For what it's worth I was told to stay away from Cobra,not a very good brand.

steco1958 · 28 April 2016, 09:49

Quote:

Originally Posted by dave3235

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

willk · 28 April 2016, 14:14

Quote:

Originally Posted by steco1958

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

Have you got one steco? They have a bit of a rep for building cardboard handhelds

You'd hope the fixed stations would be better?

Chris · 28 April 2016, 14:43

Quote:

Originally Posted by Stevie J

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.

Which Antenna are you using ?

Last Tango · 02 May 2016, 19:40

Quote:

Originally Posted by dave3235

Hi

For what it's worth I was told to stay away from Cobra,not a very good brand.

Had one in each of my last three boats.... never had a problem

I've got a dead Icom lying in the garage and another dead Icom in the garage.

What I have found useless is those little rubber aerials

Poly · 02 May 2016, 20:21

Quote:

Originally Posted by steco1958

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

As a general rule the electronics themselves work fine. They sell well because they are cheap. They probably do an OK job in the shelter of a yacht cabin. On an open boat where they get constant spray though the reputation (and my experience) is that the casings aren't build as well as the big names in the marine VHF market and so you will inevitably be replacing it at some point. Hopefully the damage comes at a convenient time...

Quote:

Originally Posted by willk

Have you got one steco? They have a bit of a rep for building cardboard handhelds

You'd hope the fixed stations would be better?

My experience with the h/helds was so bad I didn't even consider them for my fixed station. I'm fairly sure that one of our other moderators tried a fixed station that leaked!

Quote:

Originally Posted by Last Tango

Had one in each of my last three boats.... never had a problem

I've got a dead Icom lying in the garage and another dead Icom in the garage.

What I have found useless is those little rubber aerials

Your experience is relatively unusual from what people post here over the years. When people have had issues with SH and Icom they have usually find that they get sorted easily.

spartacus · 02 May 2016, 21:08

Quote:

Originally Posted by Last Tango

What I have found useless is those little rubber aerials

Can you trace fault to gubbed antenna? ICOM should be able to supply a replacement.
Miscellaneous - Icom UK

Last Tango · 03 May 2016, 13:11

Quote:

Originally Posted by spartacus

Can you trace fault to gubbed antenna? ICOM should be able to supply a replacement.
Miscellaneous - Icom UK

To clarify. The rubber antenna was one of the after-market things mounted on the "A" frame for a fixed unit. It worked but it's performance was just pi55 poor.

I suspect both the Icoms had a hard life but they were mounted inside cabins on boats I bought and were dead when I got them. One had front panel knob seized solid and the other just doesn't transmit.

I think a big part of reliability issues has to do with installation, and to be fair you won't get away with exposing the back of any fixed set to the elements. I do try to fit them where the front also gets a bit of protection and seal the mounting surface.

The Cobra hand-helds I have are really cheap and nasty but I've had them for years and they still work. I doubt they would survive a ducking but it's better it's than nothing.

MatFromPoland · 03 May 2016, 19:51

Do you have ferrites on radio cables ?
Not sure how much it helps but mine SH have them in standard.
Mount them closest to the radio and secure by tape.
Without tape they will go down.

sparkey · 08 May 2016, 09:48

The interference comes to your radio 2 ways , either via the power cable or via the co ax cable
You first need to determine which is the source

switch on the radio with the engine running and with the interference noise on the radio, and disconnect the aerial coax. If the interference stops then the interference is coming via the co ax, if it’s still there its via the power line.

You can eliminate the power line as a source by trying running the radio from a standalone battery separate from the boats battery

You will need to determine the route of the interference by using the above method before you try and eliminate it, otherwise you could be wasting your money going down the wrong route