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mobile phone interference

Started by planeman, October 07, 2012, 21:19:31 pm

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PDR

CE testing is a "self-assertion" thing. It is entirely up to the manufacturer to decide whether they are actually going to test for compliance - if they wish to they can simply make a judgement "it will probably be OK" and declare compliance on that basis.

PDR
There are no shortcuts on the long, hard road to success. But if your dad's rich there could a limo service...

Michael_Rolls

Added to which, if there are some combinations which are more susceptible than others, just imagine the vast number of combinations of Txs and phones. For a manufacturer to be willing or perhaps even able to test every possible combination seems unlikely.
Mike
Properly trained, a man can be a dog's best friend

pchristy

All CE testing does is show that *your* equipment won't cause unnecessary interference to others. It says nothing about the immunity of *your* system to outside interference from (say) mobile phones, nor does it say anything about the quality or merchantability of your system!
--
Pete
"No matter how much you push the envelope, it'll still be stationery."

GlowFly

October 09, 2012, 19:04:50 pm #43 Last Edit: October 09, 2012, 19:09:15 pm by GlowFly
Quote from: pchristy on October 09, 2012, 17:54:40 pm
All CE testing does is show that *your* equipment won't cause unnecessary interference to others. It says nothing about the immunity of *your* system to outside interference from (say) mobile phones, nor does it say anything about the quality or merchantability of your system!


I don't think that's quite right Pete. It says nothing about merchantability but there are tests for emitted RF, conducted emissions and susceptibility for mains powered equipment, and also RF susceptibility to gain CE compliance. As the other Pete said, responsible manufacturers DO test for these things so that in the event of an investigation following a complaint, they can stand up in court and feel comfortable in defending their certification. Some manufacturers now don't actually fully test, but draw on prior results for similar equipment and practice to self certify. In the exceptionally rare event of a formal complaint being followed through they would need to defend that approach and produce internal documentation to support it. Unless it was as a result of an H&S type investigation, they stand a good chance of escaping severe penalty.

It can be surprising how minor changes to a production process can introduce RF issues. I was responsible for designing a product some years ago that was tested and gained compliance. Some years into production we had a few field reports of very occasional malfunction in the vicinity of another piece of equipment. It turned out that the printed circuit had had a tiny modification introduced when a capacitor supplier changed the size of one of the components. These sort of things happen frequently during manufacture and rarely is the product subjected to a full retest. The exception has been military electronics where we ALWAYS retested following a minor change. But the taxpayer was paying and CE certification wasn't even a requirement!

pchristy

Hi GlowFly,

Well, for 2.4 GHz equipment, the standard it has to comply with is ETSI En 300 328. Looking though it (and it is mind bogglingly long and complex!), I can find plenty about spurious emissions, but other than a very brief note about receiver blocking (and that only applies to adaptive equipment operating above 10dBm eirp), nothing about susceptibility to outside interference! I think the one for 35 MHz is similar, though I can't find it at the moment (I'm at work).

Where have you seen a reference to RF susceptibility? It may be I've missed it in the vast quantity of paperwork that surrounds this.

If the EU is good for nothing else, it is good at producing paper mountains.....!!

--
Pete
"No matter how much you push the envelope, it'll still be stationery."

welshboy

Just a thought, but as most of the CE mark seems to be related to emmisions that could cause interference, shouldn't we be looking more at the mobile manufacturer? From my very limited knowledge of the regulations they seem to be related much more to emmision levels and frequencies than to resistance to interference. In other words they are there to prevent you interfering with something else not to prevent you being interfered with by a noncompliant device.

Prepared to duck as I have probably misread the situation:-[


Sent from my GT-I9300 using Tapatalk 2


Geoff N

It's getting near to Chr----mas so.
HO yes it does -- HO no it does'nt

GlowFly

Quote from: pchristy on October 10, 2012, 17:36:58 pm
Well, for 2.4 GHz equipment, the standard it has to comply with is ETSI En 300 328. Looking though it (and it is mind bogglingly long and complex!), I can find plenty about spurious emissions, but other than a very brief note about receiver blocking (and that only applies to adaptive equipment operating above 10dBm eirp), nothing about susceptibility to outside interference! I think the one for 35 MHz is similar, though I can't find it at the moment (I'm at work).

Where have you seen a reference to RF susceptibility?

Hi Pete,

I'm retired now and have gleefully chucked the entire mound of compliance data!! However I think that document you mention is an addendum referring to additional requirements for 2.4GHz devices. It's important to understand that it isn't the only document to which equipment must comply, the main EMC compliance directive applies to ALL electronic equipment sold within the EU and includes susceptibility requirements. I've just had a quick look online and didn't turn up a generic document, I might try again tomorrow. A quick call to any of the test houses will result in another mound of reading to enjoy!

We had to state to which standard our equipment should comply. Medical and food preparation kit was susceptibility tested to 10v/m field strengths and no malfunction must occur. Our industrial equipment was tested at 3v/m RF fields on a full frequency sweep, and also to induced noise on any mains supply. A threshold existed where slight malfunction could occur while the field existed but it had to recover immediately once removed.

All exposed parts of equipment such as front panels were also subject to 1kV spark tests. When we were learning we soon discovered that old fashioned methods of panel mounting LEDs simply wouldn't pass. We tried covering entire panels with translucent membranes and hiding lamps behind it or else used light pipes.
I seem to remember that the 1kV tests were removed from later revisions of the directive.

Steve

Theaton56

It's not just RF transmissions from the phone that are relevant, ALL electronic devices radiate unintentional radiation.  Remember that all these phones etc have a crystal buried in there somewhere, this will radiate, clock and data lines also radiate, pcb tracks act as an antenna.

If any of these stray signals get into a transmitter, it could cause timing issues and consequent glitches.

I used to work in identifying radiated signals, occasionally crossing over into the realms of EMC.  Have seen this phenomenon a fair few times.

One thing I will say about JR transmitters, they are fairly well decoupled to remove spurious signals.

Wiz

...and isn't it true that the transmitter mentioned in the BMFA original bulletin was Multiplex?  Could all of this be because of a poorly designed transmitter or has the phenomenon been recorded in other brands?
The buck stops here.

itsme

Quote from: Wiz on October 11, 2012, 10:28:40 am
...and isn't it true that the transmitter mentioned in the BMFA original bulletin was Multiplex?  Could all of this be because of a poorly designed transmitter or has the phenomenon been recorded in other brands?
Wiz, I have seen Futaba Txs 'altered' which are difficult to explain any other way.

pchristy

Steve,

Yes, but a lot of it doesn't apply to our equipment (stuff like mains isolation / safety / etc), and also bear in mind that as all our frequencies are "unlicensed" bands, the powers that be are not in the slightest bit interested in deficiencies in *our* equipment, as long as it doesn't disrupt anyone else's!

Welshboy,

True, but the difference is that mobile phones are *licensed* equipment. Allright, the license is held by the 'phone company rather than the individual user, but nonetheless, it is licensed equipment.

Because of the power levels required for the system to work properly, some interference is inevitable - especially at close range. If you are flying with a mobile phone on your belt or in your pocket, it is likely to be within a foot or two of your tranny (depending on your girth!!  ;) ) At such close quarters, some breakthrough is almost inevitable, unless the equipment is properly screened!

To back up what Tony is saying, I've never had an issue with JR kit. But equally, I've never had a problem with some of my older transmitters dating back to the 60s and 70s, when transmitters came in proper metal cases (which equals very good screening!) rather than plastic!

--
Pete
"No matter how much you push the envelope, it'll still be stationery."

GlowFly

Quote from: pchristy on October 11, 2012, 12:11:48 pmYes, but a lot of it doesn't apply to our equipment (stuff like mains isolation / safety / etc),


True in the case of mains isolation. But if there isn't mains you also need to claim compliance with the Low Voltage Directive, where if I remember right all voltages must be under 50v. Usually the case with r/c transmitters! Basically the stuff that goes on behind CE marking is much more involved than most people think if you were serious about it. The compliance files we had to keep on each piece of equipment were substantial.

Quotethe powers that be are not in the slightest bit interested in deficiencies in *our* equipment, as long as it doesn't disrupt anyone else's!


I agree that it is likely to need a number of reports or equipment complaints to trigger an investigation, unless accusations are made after a serious accident, but if formally/responsibly testing for CE compliance, susceptibility testing is definitely a requirement.

QuoteTo back up what Tony is saying, I've never had an issue with JR kit. But equally, I've never had a problem with some of my older transmitters dating back to the 60s and 70s, when transmitters came in proper metal cases (which equals very good screening!) rather than plastic!


I think we're agreed. I don't think it's ever happened to me on any brand but I have witnessed it on a very few occasions so I choose not to carry a phone on the flight line (unless I forget, but the sky didn't fall in when I did!). I'll bow out now since I don't see how I can contribute anything useful to the discussion.

Steve

itsme

Quote from: GlowFly on October 11, 2012, 17:04:09 pm
True in the case of mains isolation. But if there isn't mains you also need to claim compliance with the Low Voltage Directive, where if I remember right all voltages must be under 50v. Usually the case with r/c transmitters! Basically the stuff that goes on behind CE marking is much more involved than most people think if you were serious about it. The compliance files we had to keep on each piece of equipment were substantial.

I agree that it is likely to need a number of reports or equipment complaints to trigger an investigation, unless accusations are made after a serious accident, but if formally/responsibly testing for CE compliance, susceptibility testing is definitely a requirement.

I think we're agreed. I don't think it's ever happened to me on any brand but I have witnessed it on a very few occasions so I choose not to carry a phone on the flight line (unless I forget, but the sky didn't fall in when I did!). I'll bow out now since I don't see how I can contribute anything useful to the discussion.

Steve
A sensible conclusion. Its unlikely to be a problem unless you are very unlucky, but the prudent flier will leave it in the vehicle. I'll go with that.....