ferrites

[Getout]

Can anyone explain how to correctly position those clip-on ferrite things to the power cable of your sounder/GPS?

[Geoff-]

Just clip it on the wire, it doesn't really matter which end of the run but I would be tempted to put it close to the sounder as that's where you're trying to minimise interference. If the power cable is thin enough to loop it through the ferrite a couple of times then do that, it will work better.

[testlab]

Just clip it on the wire, it doesn't really matter which end of the run but I would be tempted to put it close to the sounder as that's where you're trying to minimise interference. If the power cable is thin enough to loop it through the ferrite a couple of times then do that, it will work better.


For non-networked systems, as close to the main unit as possible is normal. For networked systems ferrites may be supplied for both ends of the network cable runs.

Ferrites may be required on both power and signal/data cables - check with the makers manuals as some driven outputs (for transducers) may not tolerate ferrites and cause degraded performance due to cable impedance problems.

Ferrites reduce interference from being radiated by the units electronics and may also be required to prevent external interference (HF/MF/27Mhz/VHF/radar) from getting into the unit.

A lot of people don't fit them and when sitting at the dock it probably doesn't matter much, but get into the fringe of radio reception and EMI (electromagnetic interference) will degrade the performance of your radio receiver.

This is one reason why coast stations should have their computer installations checked and use only high quality brand name computers and monitors. Otherwsie EMI may be reducing their sensitivity to small signals (brand name computer makers must test their EMI standards compliance - small boutique assemblers don't have to).

[oldboot]

Where and what ferrites you use depends on what you are trying to achieve.

Quite a lot of the time ferrites are fitted "just in case" and do absolutly nothing of use or effect.

What are you trying to achieve.

cheers

[testlab]

Quite a lot of the time ferrites are fitted "just in case" and do absolutly nothing of use or effect.
cheers

If they are supplied (in the box) by the manufacturer you can probably bet they are in the box because without them the unit doesn't comply with the compulsory standards for limiting interference.

True, they usually don't have a noticeable effect. Liken them to a vapour canister in a car - you can't see it doing anything tangible but it must be there for a reason.

[oldboot]

If they are required for conformance with the "electromagnetic compatability framework" they should either be permanently fixed, or at least they should have specific instructions as to where and how they are to be fitted.

Ferrite surpressors are absolutly nothing like carbon canisters...the role of a carbon canister is clearly discribed,easily understood and compulsory under law.

In the past and today, lots of electronic manufacturers include all sorts of "bits" in the installation kit that may be neither required nor effective.

Back in the late 70's when I was installing car radio..... just about every one came supplied with a surpression capacitor......no discussion of what to do with the thing and I saw plenty try to install them, but I never saw one do anything effective.

These ferite bead dongas are cheap as chips, so lots of manufacturers include them or fit them, for enhanced customer satisfaction.

In real world applications they are only effective at RF frequencies and they are intended to block RF emmissions traveling on the outside of the shiled or cable bundle.

Any spurious EMR emissions or RF vunerabilties on individual wires should be dealt with within the case of the unit...and those measures should not be able to be tampered with by the user/installer.

So again what is the goal in fitting the item.

cheers

[testlab]

If they are required for conformance with the "electromagnetic compatability framework" they should either be permanently fixed, or at least they should have specific instructions as to where and how they are to be fitted.

That they should but often aren't for a variety of reasons. To meet the reg, yes instructions must be included if they are to be fitted during installation.


Ferrite surpressors are absolutly nothing like carbon canisters...the role of a carbon canister is clearly discribed,easily understood and compulsory under law.

I couldn't think of a better analogy at the time. Those mechanically minded know what a vapour canister is and why its there. Same with ferrites. You don't need either to make the equipment function.


In the past and today, lots of electronic manufacturers include all sorts of "bits" in the installation kit that may be neither required nor effective.

Back in the late 70's when I was installing car radio..... just about every one came supplied with a surpression capacitor......no discussion of what to do with the thing and I saw plenty try to install them, but I never saw one do anything effective.

Yes... I remember those days too. Those caps were indeed useless and one had to fit proper suppression of the ignition and alternator as many cars had none.


These ferite bead dongas are cheap as chips, so lots of manufacturers include them or fit them, for enhanced customer satisfaction.

Only the crappy ones that are knock off copies of properly made types are cheap. Real fair dinkum ones are damned expensive and manufacturers hate including them (so they put in cheap nasties that do nothing).


In real world applications they are only effective at RF frequencies and they are intended to block RF emmissions traveling on the outside of the shiled or cable bundle.

Any spurious EMR emissions or RF vunerabilties on individual wires should be dealt with within the case of the unit...and those measures should not be able to be tampered with by the user/installer.

So again what is the goal in fitting the item.

cheers

Yep... but often you need "braid breakers" to block those unwanted signals carried just as you say. These unwanted signals, if present still sum in radio reciever first stage amplifiers and either desensitise it or raise the noise floor, masking low level signals.

I take it the last question is rhetorical but for the sake of those reading (and still awake) I will reiterate what I said above....


Ferrites reduce interference from being radiated by the units electronics and may also be required to prevent external interference (HF/MF/27Mhz/VHF/radar) from getting into the unit.

A lot of people don't fit them and when sitting at the dock it probably doesn't matter much, but get into the fringe of radio reception and EMI (electromagnetic interference) will degrade the performance of your radio receiver.


I always suggest following the manufacturers recommendations.

Cheers
Dave.

[Getout]

Thanks for the replies blokes. I received a few of them with my Raymarine A65 years ago and the instructions were pretty vague on how to install them.
I do get a bit of interference on the VHF to the point where i have to switch off the sounder/GPs when I am using the radio outwide. I do have one clipped to the power cable neat the unit.

[TheRealAndy]

The ferrites are used mainly for EMI supression to meet standards, however they are also usefull for reducing noise on signal lines.

I used to hate the job of making electronics comply. I used to do all my inital testing at the QUT lab at gardens point, so got too see first hand how and why it all works. ITs a pain in the arse doing compliance, because sometimes you have to go as far as redesigning the whole circuit board.

[testlab]

The ferrites are used mainly for EMI supression to meet standards, however they are also usefull for reducing noise on signal lines.

I used to hate the job of making electronics comply. I used to do all my inital testing at the QUT lab at gardens point, so got too see first hand how and why it all works. ITs a pain in the arse doing compliance, because sometimes you have to go as far as redesigning the whole circuit board.

And until recently this was how I made my living - testing and/or redesigning for compliance for international manufacturers, including small engine powered equipment, and a few outboards too (we also did OEM design srvices, which I now do exclusively for one Australian company).

These days the lab is available for only a few clients insted of a fully public available test house. However the lab is still a fully capable electrical safety, EMC, radiocommunications, telecommunications, electromagnetic radiation, environmental (temp, humidity and salt spray), vibration for small equipment (max 10kgs), flammability, energy rating, water rating, luminance and chrominance, noise and acoustics (limited scope in these last two). Its was a A$5M investment and built up over 30 years from a business I started in high school (with zero Govt ownership/input/assistance unlike others in the game).

If you're ever going to be in Sydney's northwest drop me a note and come have a look. It's not as impressive as it used to be when in full operation but all the flashing lights still look kinda cool. ;D

[testlab]

Thanks for the replies blokes. I received a few of them with my Raymarine A65 years ago and the instructions were pretty vague on how to install them.
I do get a bit of interference on the VHF to the point where i have to switch off the sounder/GPs when I am using the radio outwide. I do have one clipped to the power cable neat the unit.

One of the reasons why the instructions are vague is because one needs experience which can't be passed on in simple "clip it on" instructions.

In my experience the problem you've described is usually because the power cables for everything and possibly also antennae cables are bundled together. Good practice for radio installations involves separating radio power cables from digital electronics and the engine instrumentation loom (a separate power feed from the batteries is best). Antennae cables should be routed well away from other cables.

Poor antennae performance will also make the radio systems more susceptible to noise. The VSWR should be checked occasionally to make sure the ground plane, co-ax cable, connectors and antenna are not degraded. Most marine electronics shops can do this with a simple SWR meter.

If the noise is a real problem to you, PM me and I'll send you a few different ferrites to try. I still have a few samples of different types laying around.

Cheers
Dave

[Geoff-]

These ferite bead dongas are cheap as chips, so lots of manufacturers include them or fit them, for enhanced customer satisfaction.

In real world applications they are only effective at RF frequencies and they are intended to block RF emmissions traveling on the outside of the shiled or cable bundle.

Any spurious EMR emissions or RF vunerabilties on individual wires should be dealt with within the case of the unit...and those measures should not be able to be tampered with by the user/installer.

Why would a manufacturer include something which the customer has no real idea how to use, just for the sake of it? It costs them more to put it in the box, it is definitely there for regulatory compliance. It'll also work fine without it, just won't be compliant but that's not the manufacturer's problem as the installation wasn't done properly if the ferrite is omitted. Customer doesn't care because it works anyway.

Would be nice if all the required filtering was internal but sometimes it's not practical. Or if you only just fail compliance then the addition of a ferrite may get you through and that's a lot cheaper than a PCB redesign.

[oldboot]

Th onus under the "electromagnetic compatability framework" is on the manufacturer and the australian distrubuter........If they are to satisfy their obligations under the act and guidelines any required supression would need to be permanantly fitted or at least specific instructions included specifying that they must be fitted and how.
And the "Electromagnetic Compatability" of the item is definiteny the responsibility of the manufacturer or distributer, not the installer or user.

Why do manufacturers put carp in the box......good question....but plenty of em do.

I can buy these things in onesies and twosies for about $1 -2.......purchased in quantity out of china they will probaly cost 10 or 20 cents if you are unlucky.......if ya think the ones packaged with consumer grade marine equipment are more expensive than that you are dreaming.

As for checking SWR on 27Mhz or VHF marine radio.....most of the marine aerials we use are ground independednt can not be field tuned and show poor SWR figures at the best of times.

Most marine installers are unqualified and would have no RF test instruments what so ever, a good multimeter if you are lucky.

Properly competent marine installers are the exception outside the commercial area.

World wide the vast majority of consumer grade marine electronics will be either self installed or installed by unqualified people and this is well and truly known.
So it is unreasonable to expect something required for compliance to be fitted by the installer.

By consumer grade I mean any thing that is sold in a box with a pretty picture on it and available to the general user.

As far as experience required to fit one of these cheapy ferites.....OH dream on.......you know as well as I do....... even the smartest and most experienced people either take a punt or fit these things by trial and error.....nobody not even the highly tooled up commercial installers would have instruments capable of measuring and installing these by analisis in the field.

Almost with out exception they are best fitted as close as possible to the cable entry on the equipment.

Face it... clip on ferites realy are not a high order RF supression device, they are mostly cheap and nasty afterthaughts, are marginaly effective at best and the vast majority sold and fitted perform no usefull and effective function.

Ya might find a few situations where they ( not permanantly fitted at manufacture ferites) help a little in a consumer marine installation.....but I recon it would be rare to find a proven case.

cheers

[TheRealAndy]

Th onus under the "electromagnetic compatability framework" is on the manufacturer and the australian distrubuter........If they are to satisfy their obligations under the act and guidelines any required supression would need to be permanantly fitted or at least specific instructions included specifying that they must be fitted and how.
And the "Electromagnetic Compatability" of the item is definiteny the responsibility of the manufacturer or distributer, not the installer or user.



Compliance is achieved via a sample to the test lab. Once it complies, thats it. As long as the suppression device is supplied, there nothing more the manufacturer has to do.

Its quite common to do this, as you often have to run cables and moulding a suppression device onto a cable is not always practical.




Why do manufacturers put carp in the box......good question....but plenty of em do.

I can buy these things in onesies and twosies for about $1 -2.......purchased in quantity out of china they will probaly cost 10 or 20 cents if you are unlucky.......if ya think the ones packaged with consumer grade marine equipment are more expensive than that you are dreaming.

As for checking SWR on 27Mhz or VHF marine radio.....most of the marine aerials we use are ground independednt can not be field tuned and show poor SWR figures at the best of times.

Most marine installers are unqualified and would have no RF test instruments what so ever, a good multimeter if you are lucky.


SWR is measured on Ground independent antenna's the same was it is measured on ground plane antenna's.



Properly competent marine installers are the exception outside the commercial area.

World wide the vast majority of consumer grade marine electronics will be either self installed or installed by unqualified people and this is well and truly known.
So it is unreasonable to expect something required for compliance to be fitted by the installer.

By consumer grade I mean any thing that is sold in a box with a pretty picture on it and available to the general user.

As far as experience required to fit one of these cheapy ferites.....OH dream on.......you know as well as I do....... even the smartest and most experienced people either take a punt or fit these things by trial and error.....nobody not even the highly tooled up commercial installers would have instruments capable of measuring and installing these by analisis in the field.

Almost with out exception they are best fitted as close as possible to the cable entry on the equipment.

Face it... clip on ferites realy are not a high order RF supression device, they are mostly cheap and nasty afterthaughts, are marginaly effective at best and the vast majority sold and fitted perform no usefull and effective function.

Ya might find a few situations where they ( not permanantly fitted at manufacture ferites) help a little in a consumer marine installation.....but I recon it would be rare to find a proven case.

cheers

I guess you have never sat in a test lab measuring radiated energy. clip on ferrites are very effective and do the job very well. Its pretty rare for these to be an afterthought, when you design something that has cables emitting signals, you can be fairly confident that you will need some sort of rf suppression on the cable.

[Getout]

If one does the job, do two do it better?

[TheRealAndy]

If one does the job, do two do it better?

Nope. One is all you need.

[testlab]

I don't want to prolong the argument but for the benefit of people reading here without knowledge of the field there are some do's and dont's. I have outlined some basic info above - its based on my experience in the field, which includes qualifying transmitter/receiver installations.

If the ferrites are in the box.. use them... and to get the best result you will have to experiment with the place to put them. A big ferrite placed around a loop of bundled cable can make a big difference in some installations.

Lastly, the ferrrite in the box may not be the best one for your particular needs (assuming you are trying to get the best radio reception/least interference possible). It is selected to make the device comply with a standard, but that only applies in a precisely configured test situation. The way a vessel is wired and laid out makes a huge difference and no two are identical.

When out wide, try clipping the ferrite(s) on and off the power cables (or the antenna cable) in different places and see if it reduces the radio receiver noise.

As for SWR... ground independent antennae are not individuaslly tuned (cut) like those used on motor vehicles. But an SWR test will show if a particular antenna setup has degraded (even better still would be a proper reverse power measurement but that's getting expensive and specialised).