ssb interferance

[Tiller 2]

ssb interferance from speedo impellor. when speedo off ssb fine .anyone know how to remedy this.

cheers

[wheels 543]

Can you explain just a little more.

Does the interference exist if the boat is stationary with speed unit turned on?

Does the interference sound change with speed?

[Tiller 2]

happens while boat is sailing

[Guest]

Will have to check on wednesday what happens in the marina with out the boat sailing.

 

Speed was around six knots both times I tested and and was the same noise/interference.

 

Was sweet as with instruments off.

[wheels 543]

Righty then. how the thing woirks is that it has a little magnet in one of the paddles. In the body is a magneticaly activated switch. How the signal is sent to the head unit varies on makes. But normally 5V is placed on wire.This 5V can be switched by the mag switch back down the other signal wire, shorted to 0V or turned into a digital signal with a little more complex switch/circuit.

The reason I ask about is the noise there when stationary, is because that tells me if it is the head unit or the cable to the transducer. The circuits that drive the LCD display can create RF noise. But this sounds like it is the cable.

Some cables can have two signal wires and a shield wire. The Shield is supposed to stop noise radiating out. So ensure you don't have a broken wire in the plug. Unless you have put strain on that cable or dropped something on it, it would be pretty hard for the cable itself to have the wires inside damaged.

The other thing is to try dressing the cable further away from the other cables in the boat. Especially if it happens to run parrelel to anything connected with the SSB, or if the lead runs beside the SSB.

I am assuming the SSB is working OK otherwise. Because the onlyt other thing to check would be the SSB earth. But as the SSB earth is part of the Transmitters Antennae, you would not be getting it to tune properly and you would also run the risk of blowing the output stage.

I am assuming this problem is reletively new.Has anything been changed anywhere lately that you might be able to pin thought to??

[Guest]

Were any lights, specifically LED's, turned on at the same time as the interference?

 

Some have a DC-DC converter in them which has recently been found buggerising around with radios i.e causing interference.

 

Wild stab there but might knot be if you have changed any lights lately? They are something most wouldn't think to think of.

[Guest]

yes new led nav lights last week.

and new wiring in most of the boat.

 

Will do more looking at it on wednesday but it definately does it whilst stationary on the marina.

 

ssb works 100% when no instruments on. Not sure about when the nav lights are on will check that too.

Would sheilding the ssb wire that goes to the aerial help?

And what sort of wire should that be?

[Tiller 2]

maybe its the wind speed indicator thats why it going in the marina.

[Absolution 7]

...or if the noise is a regular pulse i.e a pulse every 0.2 to 0.5 second then it's probably from your depth sounder.

[wheels 543]

Sorry Skins, i saw Tillers reply and thought it was yours.

Yes you need to carry out a process of elimination. As KM said, LED's can do it. It depends on the type of regulator they use.

Ummm, the SSB cable to the antennae should be Coax. If it is not then the wire all the way from the Radio transmiter is transmitting and could put noise into other things when you transmit. But worse, the actual working area of antenna is not up high working at it's optimum.

[Guest]

yes new led nav lights last week.

and new wiring in most of the boat.

Ah, that is interesting.

 

I first saw reference to it in a MSA thing about a commercial boat, there was an article in Pro Skipper I posted here somewhere. At the same time it also suddenly explained why the radio went fuzzy when you turned on one light in the new micro-dwelling. The same thing in both.

 

From what I understand it's most likely to be the masthead light but could be any I suppose.

[wheels 543]

It certainly could be any or all LED's. But one reason why the Masthead lights cause a problem is the very long length of cable acting as an antenna. One particular manufaturer has an issue with their Tri-colour light. LED's are current devices. So the Tri-colour is probably drawing more current and thus the regulator is putting oput more RF crap.

It differs greatly between products, and just because on puts out noise, does not mean it is cheap and nasty. What is it does mean is that it has a complex regulator. Heat is the biggest enemy of the LED. The more heat, the less life. The more light you try to produce from them, the more heat they produce and so the less life they have. One way of improving the brightness is to switch the LED light on and off. If you can switch it on and off fast enough our eyes don't see any flicker, we just see light. So lets say you can switch it off for 0.5sec and on for 0.5sec and off again and on and so on, then you can say that the light is now being swithed off for 50% of the time. So it now produces 50% of the heat. So now if it is possible, we could apply 50% more current and produce 50% maybe, more light output. At 0.5sec intervals, we would see the flicker. But if we speed it up to thousandth's of a second, we don't see any flicker. The light is still saving energy, although not as much as being off for 0.5 of a sec. But is still helps. So the little regulators are working fast and as they swtich, they produce spikes.These spikes occur so fast, we hear it as a noise on any RF recieving device that just happens to be sensitive enough and tuned in someway close to a wavelength or even part of a wavelength.

The NZ Radio Spectrum Management board are trying as hard as they can to keep up with the new stuff coming in to NZ and the new technology. And it would be safe to say, they aren't keeping up. LED's are supposed to meet CE requirements. But much of the stuff coming from China has a sticker put on it but it has never been tested. And lots are being imported witout proper testing and clasification. RSM would like to have people contact them with the name of the LED that gives off intefrence so as they can try and sort it.

So what can be done?? Well that is a really hard one to answer, because it is complex. The makers of the Tri-colour with the problem, have come up with a solution for that LEDm only. The remedy may well work for most if not all situations. But it is finding the right one that suits. That is a small ferrite bead placed in the power lead as close to the LED as possible. But it needs to be the right size as what is being created here is a Tuned filter. It is tuned to filter out that specific frequency being created by the LED.

But it could well be worth a shot to go get some small ferrite cores from say Dick Smiths and try. You need to wrap the power wires through the bead two complete turns.

However, it is important to ensure all your wiring is laid out well. That all equipment that is supposed to be earthed is and that if the SSB has an earthing point on the case other than the arial earth, then you need to connect that. You need to sort that cable going to the Backstay and make sure it is Coax. That may well sort all your problems.

[aklsailor 1]

Sooo will the interferance be coming through the aerial cable or is it coming through the power supply? Could a seperate feed from battery to ssb help? Also can you use RG6 coax for aerial connection?

[Guest]

its definately not led nav lights.

but depth could be a fair call as could be the wind gear. I'll pull the log out and turn it off to eliminate that.

 

Currently there are about four switches for every single thing thats electrical on the boat and I think thats probably a bit rangi having so many different things wired together. plan to change that in the next couple weeks.

What do most people use for the backing boxes on the switch boards if you dont have a bulkhead to mount on.

I havn't seen any thing for sale to fit the standard 12 switch panels.

Funny how dodgy wiring can get you by untill you really want it to work reliably and for more than a 12hr coastal.

[wheels 543]

Also can you use RG6 coax for aerial connection?

No. And just what you use depends of the Radio model and if the tuner is Auto or manual and biult in or seperate. For instance, some have to have a single wire. But normally it is a special wire used. It has a high voltage insulation jacket or something like 15000V. That is because you are dealing with RF. Some units that have a seperate Auto tuner, often has a special coax connecting the Tuner to the Transmiter.

The best info is to look up the installation manual for your make and model of radio.

[Guest]

So it is the auto helm rudder sensor causing the problem and it runs down the starb side about a foot away from the ssb.

Going to re route it.

 

And the ssb aerial is just plain conduit wire and it works fine.

[Guest]

Interesting - There was a thread that involved autohelm rudder sensor interference on here a few years back, sounds like the same. I think its in the old version of crew.

[Guest]

It was a Wellington sailor who was prepping for the solo NP to Moolalooba race. It will be in the topic discussing that race I guess.

There was a newer version of the helm position sensor that fixed the interference with better screening.

[Guest]

Thats the one - Island Time was the boat/user name?

[Guest]

Yep, that's it.