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mobile phone interference

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

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planeman

I have heard a rumour of interference to 2.4 Ghz radios from mobile phones in the pockets of flyers.  I do not want to add to this hearsay, if that is what it is but I would like to know if such is possible, as it was with 35Mhz.  Is there an authoritative voice out there who can advise?  Please no guess work or opinions, just the facts.

itsnoteasy

 I must say I have flown with mine in my pocket and no Problems you my well have  been very close .. ::)

PDR

The interference that was suspected (and occasionally demonstrated) in 35MHz radios appeared to afflict the "logic" part of the Tx (the processor and memory) rather than the RF section, so in principle the potential problem could be no better or worse. The only difference with 2.4GHz transmitters is that they may have better "designed in" general protection against microwave signals as they generate them internally. I say "may" because it's not clear that such testing is always done, and where an existing 35MHz radio is switched to 2.4GHz simply by changing the module it usually involves no changes to the logic parts of the Tx at all. There are exceptions - when Multiplex transmitters are serviced there have been minor modifications for this sort of thing (like the extra capacitors that were fitted to the slider pots on Evo radios recently), but I don't know if other manufacturers are doing similar mods.

The safest assumption is that if you have a transmitter that is reputed to have this kind of sensitivity (the P4000 and FF9C being ones that spring to mind) then keep your phone away from it just to be safe. You could trawl through the CE certification datapack to see if this specific compatibility has been tested, but to be honest those datapacks can be pretty incomprehensible to non-specialists!

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

Geoff N

Moulded gliders +Jr9x2 +frsky 2,4 + mobile + 18 months = no problems

Bad Raven

Rumour?  OK, no definitive statement, but if you read your BMFA Handbook.......................

Mobile Phones
(a) Although mobile telephones operate on frequencies far removed from our model control frequency bands they are a major addition to the increasing background radio 'noise' that our equipment has to filter out. In addition, there is some evidence that there may sometimes be an interaction between mobile 'phones and microprocessor controlled transmitters.
(b) Many mobile 'phones transmit powerful signals regularly even when on standby and BMFA recommends that they are not taken into the pits area and especially not on to the flying area. Many 'phones also emit a powerful signal pulse when switching off, which is also something you may have to consider. Your radio equipment has a hard job to do filtering out background RF radiation and you could make it much worse with your mobile 'phone.



Which pending better info is enough to cause a degree of caution to be prudent?

What I HAVE seen is people using a phone WHILE THEMSELVES FLYING!!
The user formerly know as Bravedan........... Well if Prince can do it....................

itsme

Futaba Txs were reputed to suffer from the eprom memory being altered/wiped by close proximity to mobile phones, and a lot of clubs (including ours) became quite paranoid. However, I have not heard of an incident for some time, and my mobile is often in my pocket while using my FF9 with 2.4 module, It has never happened to me, however, I have come across some mysterious incidents where failsafes have become reversed- is that a possibility?

Michael_Rolls

A few years back there were a number of reported instances in which interference of a Tx by a mobile phone seemed a probability. IIRC all were in the days of 35. Have to admit that after getting a bit twitchy over it at the time and always leaving my phone in the car, nowadays it is always in my pocket at the field.
On the question of folk using a phone whilst actually flying - back on here at the time when folk said 'But I have to have my phone available at all times' I responded with'So if it rings will you answer?' one or two said, effectively, yes - how is it different from using the phone whilst driving/ (!!  :banghead: :banghead:).
Mike
Properly trained, a man can be a dog's best friend

itsme

Quote from: Michael_Rolls on October 08, 2012, 08:31:43 am
A few years back there were a number of reported instances in which interference of a Tx by a mobile phone seemed a probability. IIRC all were in the days of 35. Have to admit that after getting a bit twitchy over it at the time and always leaving my phone in the car, nowadays it is always in my pocket at the field.
On the question of folk using a phone whilst actually flying - back on here at the time when folk said 'But I have to have my phone available at all times' I responded with'So if it rings will you answer?' one or two said, effectively, yes - how is it different from using the phone whilst driving/ (!  :banghead: :banghead:).
Mike
yep, I must admit I had not thought of that, hopefully I'm not stupid enough to try it!

RobC

I am often on-call for work on flying days, so I need to keep my phone in my pocket.  If it rings, I simply land then call work.  It's just like when driving a car - pull over somewhere safe and then call them back.
I've got to add that I've been called a couple of times while using my FF9/FrSky tx without any apparent problems.
flying's easy - it's getting it back down in one piece that's the hard part

Sizzling

I will admit to having my phone on me most times I fly. This is something I have done when I used to fly 35mhz (Futaba 9 Zap) and on 2.4 (JR DSX9). I have never had a problem and it has rung and I have even answered it  :o but it was hands free.

The reason I have my phone on me is I have all my music on my iPhone and I enjoy practicing flying to music. This is why in the instance where I actually answered a call (I was expecting an important call) it was handsfree.

Wiz

I think perhaps the rumour alluded to in the original post refers perhaps not to the issue of RF interference as such but rather to the fact that some (most?) smartphones these days have the capability to connected to a wireless network on 2.4GHz which is of course the frequency most of us fly on and therefore some bright spark put two and two together and made 5!
The buck stops here.

markg

Quote from: Michael_Rolls on October 08, 2012, 08:31:43 amhow is it different from using the phone whilst driving

"similar, except probably a thousand times less dangerous"

Bad Raven

Quote from: markg on October 08, 2012, 10:42:12 am
"similar, except probably a thousand times less dangerous"


In terms of the number of people you might hit directly with the plane, possibly, but most of us fly in a crowded infrastructure.

And if you'd seen someone flying erratically while talking on a hand held mobile with the Tx in the other hand, unable to alter the throttle, as I have more than once, you might reduce the odds.............
The user formerly know as Bravedan........... Well if Prince can do it....................

itsme

Quote from: markg on October 08, 2012, 10:42:12 am
"similar, except probably a thousand times less dangerous"
unless its you in the path of an out of control model... there are millions of people who still use mobiles while driving (I know its stupid, but you see it all the time) and thankfully, few accidents. I'm not sure about the 'thousand times' bit, Mark....

markg

October 08, 2012, 11:07:06 am #14 Last Edit: October 08, 2012, 11:09:48 am by markg
Quote from: bobt on October 08, 2012, 10:53:19 am
unless its you in the path of an out of control model... there are millions of people who still use mobiles while driving (I know its stupid, but you see it all the time) and thankfully, few accidents. I'm not sure about the 'thousand times' bit, Mark....

I'm not advocating using a phone while trying to fly but equally I wouldn't start fearing for my life if I saw someone doing it, just in my own personal risk assessment it doesn't seem deadly dangerous.  Basically RC planes just aren't generally all that dangerous.  If you were driving along and you just closed your eyes and began randomly poking at all the controls until there was an accident then you would be pretty lucky if nobody got hurt.  If you did the same with a plane then you would be pretty unlucky if someone did get hurt.

I've seen people fly planes badly for all sorts of reasons, chief among which being a chronic shortage of ability.  I've never felt scared or wanted to ask them to stop it, though.  (obviously my own risk assessment varies according to model type and location, so if it were someone flying a 1:2 scale Lancaster Bomber at a crowded show then I'd probably be keeping a keen eye on the thing)

Jeezeypeeps

Quote from: Bad Raven on October 08, 2012, 07:43:57 am
Rumour?  OK, no definitive statement, but if you read your BMFA Handbook.......................

Mobile Phones
(a) Although mobile telephones operate on frequencies far removed from our model control frequency bands they are a major addition to the increasing background radio 'noise' that our equipment has to filter out. In addition, there is some evidence that there may sometimes be an interaction between mobile 'phones and microprocessor controlled transmitters.
(b) Many mobile 'phones transmit powerful signals regularly even when on standby and BMFA recommends that they are not taken into the pits area and especially not on to the flying area. Many 'phones also emit a powerful signal pulse when switching off, which is also something you may have to consider. Your radio equipment has a hard job to do filtering out background RF radiation and you could make it much worse with your mobile 'phone.


That read like something put together for a bygone age with few facts to back it up.  Mobiles operate on frequencies "far removed" from those used by models, but they are also "background noise" that our equipment has to filter out  :af. So the frequencies are both "far removed" and close enough to be a problem?

Mobile phones transmit powerful signals when "on standby" and a "powerful signal pulse" when switching off? Really  :'' First I've heard of it.

stukno

I am still flying on 35meg so this may not apply to later 2.4 sets, but I had a couple of models going into momentary failsafe earlier this year.  The trail to find the cause was both long, expansive and expensive.

To cut to the chase, I am satisfied now that the cause was my mobile phone on my belt. I have had my phone on or about me for years but changed to a Blackberry this year. It was then I discovered that 'not all phones are the same'

Since keeping the phone well away from me while flying, normal service has been resumed!

stu k

CF-FZG

Quote from: Jeezeypeeps on October 08, 2012, 11:34:27 am
Mobile phones transmit powerful signals when "on standby" and a "powerful signal pulse" when switching off? Really  :'' First I've heard of it.


Yes really ::)

They transmit on a regular basis to maintain contact with a cell tower(s), or else how is the system to know which tower to transmit from, (or do you think every tower transmits your incoming calls and hopes it gets one of them right $%&,
Also, they transmit when you switch off to let the system know your phone is 'off' and send a busy signal if someone tries to call you.


Mark.
Paint will not hide imperfections, it will just change their colour!

RGN

Quote from: stukno on October 08, 2012, 18:20:02 pm
I am still flying on 35meg so this may not apply to later 2.4 sets, but I had a couple of models going into momentary failsafe earlier this year.  The trail to find the cause was both long, expansive and expensive.

To cut to the chase, I am satisfied now that the cause was my mobile phone on my belt. I have had my phone on or about me for years but changed to a Blackberry this year. It was then I discovered that 'not all phones are the same'

Since keeping the phone well away from me while flying, normal service has been resumed!

stu k


I work in a company that has lots of audio conferences and where many have a BB company phone and their own mobile (usually not a BB).

Whenever there is interference on an audio call it is virtually guaranteed that there is a BB near one of the star phones or on a desk near a phone. Moving it away cures the problem. Other mobiles (Android, iPhone and older phones) seem to have no effect at all, or perhaps just the very faintest interference.

This is the same at my home desk - I always have my mobile on my desk and there is never even a hint of interference on my PC speakers - but I can't have the BB on my desk or the interference is deafening!

I have no idea what the reason for this behaviour is but it is very clear that something is very different on BBs!

Richard
"I always cheer up immensely if an attack is particularly wounding because I think, well, if they attack one personally, it means they have not a single political argument left." - Margaret Thatcher

planeman

Interesting responses although we seem to have diverted into discussing the relative stupidity of phoning whist driving/flying.  Both seem stupid to me.
I have had some information directly from an 'authoritative source' which reads as follows

Hi

Short answer no.

Longer answer is that the WiFi on your phone does operate at 2.4GHz. However it will only transmit if it finds itself in the coverage of a WiFi access point. The phone will not transmit in that band if there isn't an access point within range.

Your phone does transmit at other frequencies whilst normally on and there theoretically could be some harmonics at other frequencies. However since the phone needs 2.4GHz free for it to operate on WiFi you can assume this is all filtered out.

The only other possibility is Bluetooth which also operates around those frequencies. However that is very low power and I'd be surprised if it could interfere.


Any comments?

PDR

Quote from: planeman on October 08, 2012, 19:16:52 pm
Any comments?


Just one. You are only considering the phone interfering with the transmitter's output signal. AFAIK no one has ever suggested this is a significant problem. The *significant* risk that of the phone output interfering with the microprocessor devices in the transmitter - an electromagnetic susceptibility. This is very possible and in some cases (specific phone and specific transmitter) has been demonstrated in a repeatable test. It's nothing to do with wifi on the phone; it's just the phone's microwave signals inducing currents in microprocessor circuitry - again, a known potential susceptibility where it isn't explicitly designed out.

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

PDR

Quote from: RGN on October 08, 2012, 19:03:21 pm
I work in a company that has lots of audio conferences and where many have a BB company phone and their own mobile (usually not a BB).

Whenever there is interference on an audio call it is virtually guaranteed that there is a BB near one of the star phones or on a desk near a phone. Moving it away cures the problem. Other mobiles (Android, iPhone and older phones) seem to have no effect at all, or perhaps just the very faintest interference.


We do much the same and get the same issue - not just with blackberries but with pretty well all GSM phones. They periodically re-identify themselves to the cell (or perhaps it's the call poling the phones; I don't know) but the sound is very distinctive and happens for any phone that's within a couple of feet of a starphone. I often get the same thing on the car radio when the phone re-synchs, and that's tuned to 92.5MHz (nowhere near the GSM frequencies). It's to do with harmonics, intermodulation products (heterodyning)  and so forth - it's not just a matter of "being on a different frequency band".

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

Jeezeypeeps

Quote from: CF-FZG on October 08, 2012, 18:50:35 pm
They transmit on a regular basis to maintain contact with a cell tower(s), or else how is the system to know which tower to transmit from, (or do you think every tower transmits your incoming calls and hopes it gets one of them right $%&,
Also, they transmit when you switch off to let the system know your phone is 'off' and send a busy signal if someone tries to call you.


...which rather misses the point. Mobile phones transmit all the time. the text implied that they were doing something other than what someone might expect when they are on 'standby' and when being switched off. Do you still get phones that have a 'standby' mode anyway? Every phone I've had for the past 10 years or so is either on or off.

JohnP

Quote from: Jeezeypeeps on October 08, 2012, 22:24:06 pm
Mobile phones transmit all the time.


No they don't. 

Obviously when making a call they transmit,  but when not calling or texting (or surfing the net on a smartphone etc.) they are not transmitting.  Except that every 30 mins or so (time is probably network-dependant) they transmit briefly to update the network with their position and status.  Also when switching on or off they transmit briefly to update the network.
Quantum est in fenestra canini ?

Pup Cam

And so to the real crux of the original post.   

Does the Electro Magnetic Susceptibility relate only to corruption of data during Tx operation or can it / does it corrupt the EEPROM data (ie the memory) at any time?  If so, what is the minimum separation distance that should be maintained at all times?   

If it is  < say 1m I wouldn't mind betting, and I'm not a betting type, that 99.9999% of us will have exposed our Tx to this potential hazard more than once at some point.    Perhaps the Smart phone telemetry concept with the phone stuck to the Tx is not such a good idea!

Alan
Still distracted by a 1953 AJS 16MS and now a 1939 BSA 250 too!

RGN

The BMFA have had two safety bulletins in this regard. They seem to indicate that the memories can be erased by mobile phones.

See here http://www.bmfa.org/news/bulletins/index.html

Richard

"I always cheer up immensely if an attack is particularly wounding because I think, well, if they attack one personally, it means they have not a single political argument left." - Margaret Thatcher

itsme

Quote from: RGN on October 09, 2012, 07:38:33 am
The BMFA have had two safety bulletins in this regard. They seem to indicate that the memories can be erased by mobile phones.

See here http://www.bmfa.org/news/bulletins/index.html

Richard
I agree. I have come across odd things like failsafes reversing and even ailerons, and in one case a load of memories being wiped which is enough 'evidence' (ok, not court of law stuff) to keep a mobile at least a couple of feet away from a Tx- saw one guy arrive at the field with his phone resting on his Tx on the front seat of his car.....

PDR

Quote from: Pup Cam on October 09, 2012, 07:23:34 am
Perhaps the Smart phone telemetry concept with the phone stuck to the Tx is not such a good idea!


This is something I have expressed concern about in the past, but my comments have been badged "scaremongering" and "negativism" by those who (whilst they hold power in this forum) aren't qualified to judge on matters of engineering science.

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

itsme

Quote from: markg on October 08, 2012, 11:07:06 am
I'm not advocating using a phone while trying to fly but equally I wouldn't start fearing for my life if I saw someone doing it, just in my own personal risk assessment it doesn't seem deadly dangerous.  Basically RC planes just aren't generally all that dangerous.  If you were driving along and you just closed your eyes and began randomly poking at all the controls until there was an accident then you would be pretty lucky if nobody got hurt.  If you did the same with a plane then you would be pretty unlucky if someone did get hurt.

I've seen people fly planes badly for all sorts of reasons, chief among which being a chronic shortage of ability.  I've never felt scared or wanted to ask them to stop it, though.  (obviously my own risk assessment varies according to model type and location, so if it were someone flying a 1:2 scale Lancaster Bomber at a crowded show then I'd probably be keeping a keen eye on the thing)
dont want to go off topic here Mark, but surely you can apply that one to drivers!

Wiz

Quotebut my comments have been badged "scaremongering" and "negativism" by those who (whilst they hold power in this forum) aren't qualified to judge on matters of engineering science.


...is that me?

I use my iPhone strapped to the top of my Hitec Aurora 9 transmitter for telemetry porpoises but I always have it in "Flight mode" which means it's not transmitting or receiving.  I'm sure all smartphones have this capability so if you do use it in the way that I do, that's the answer.  I have no idea if the concerns around mobile phones and programmable transmitters are founded but it just seems like common sense to me to keep two sources of RF away from each other where possible.
The buck stops here.

Bad Raven

Damn those Aquatic Mammals, Douglas Adams was right!!  (Porpoises, one of Autocorrects better efforts)   ^-^

Wiz, I'm confused now, how can something that does not transmit or receive be used for telemetry??
The user formerly know as Bravedan........... Well if Prince can do it....................

w8racer

Quote from: Bad Raven on October 09, 2012, 09:08:00 am
Wiz, I'm confused now, how can something that does not transmit or receive be used for telemetry??

The Hitec Aurora has telemetry, so I would guess that Wiz is using his phone as a display device.
Robert Welford

Sizzling

Quote from: Bad Raven on October 09, 2012, 09:08:00 am


Wiz, I'm confused now, how can something that does not transmit or receive be used for telemetry??


I believe the Hitec telemetry has a dongle that plugs into the iPhone. The iPhone itself is not transmitting but the dongle will be.

pchristy

PDR is absolutely right when he says that the problem is not interference with the 2.4 GHz signal, but with the logic circuits in the transmitter.

A mobile 'phone ramps its power up and down depending on the feedback it gets from the cell tower. It will always use just enough power to maintain a signal. This means that if you are out in the sticks (as are most flying sites!) it will probably be transmitting at full power, which can be several watts! The reason that it doesn't run the battery flat is because the output is pulsed, with a fairly low duty cycle, so the *average* power is pretty low, but the *peak* power can be very high, and it is those short bursts of peak power that cause the damage.

I've actually witnessed a large turbine-powered helicopter go in due to mobile 'phone interference, something that we managed to demonstrate conclusively after the event!

Having said that, there is no doubt that some 'phones are worse offenders than others, and that some transmitters are more susceptible than others.

I'm sure most of us have heard the characteristic "morse code" like buzzing breaking through on car radios or computers just before a call comes in, and it is that that causes the disruption. Imagine that being superimposed on top of your transmitted signal, and you will understand why the receiver goes awol! And even if a call is not coming in, a mobile 'phone still checks in with its base station regularly, just to let it know that its still around!

So, if you really want to be safe, leave your phone in the car when you go to the flight-line. But if you have been flying with your 'phone on for any length of time without any issues, then you probably have a safe combination and don't need to worry too much. As with so many such decisions, at the end of the day its your call!
--
Pete
"No matter how much you push the envelope, it'll still be stationery."

Jeezeypeeps

Quote from: JohnP on October 09, 2012, 01:05:50 am
No they don't. 

Obviously when making a call they transmit,  but when not calling or texting (or surfing the net on a smartphone etc.) they are not transmitting.  Except that every 30 mins or so (time is probably network-dependant) they transmit briefly to update the network with their position and status.  Also when switching on or off they transmit briefly to update the network.


Jeeeeeezus - is it national pedants week or something  ;D . When I said "all the time" I didn't mean every millisecond of every day. What you have said concurs exactly with how I understood they worked; it just isn't accurately refelcted in the BMFA statement.

I'l give up now  :study:

itsme

Quote from: Jeezeypeeps on October 09, 2012, 09:48:51 am
Jeeeeeezus - is it national pedants week or something  ;D . When I said "all the time" I didn't mean every millisecond of every day. What you have said concurs exactly with how I understood they worked; it just isn't accurately refelcted in the BMFA statement.

I'l give up now  :study:
Maybe not, but on reading this thread through, it seems the BMFA are giving the right advice!

Big A

Quote from: Jeezeypeeps on October 09, 2012, 09:48:51 am
When I said "all the time" I didn't mean every millisecond of every day. What you have said concurs exactly with how I understood they worked; it just isn't accurately refelcted in the BMFA statement.
Which bit isn't accurate? Seems to recognise the concerns that have been raised here.

FrankS

I never fly with my mobile in my pocket, the last thing i want is work interfering with my flying  :D

GlowFly

It should be clear by now that mobile phones have the potential to interfere with R/C transmitters. That's not to say that's it's likely but I have witnessed it on a handful of occasions with a couple being repeatable. Sure a mobile shouldn't interfere with a Tx but it can happen and very occasionally does.

As to whether it directly affects a Tx non-volatile memory I think the answer is probably not directly, but can do so indirectly because of the way Txs save their settings on power down. So if a Tx has suffered a corruption of some bit of internal memory holding current working values, the corrupted bit can get saved permanently at the same time as other data is saved. This might be because a trim has been tweaked and the value needs to be saved, or automatically since some Tx CPUs remain powered even when the power switch is turned off, and save their settings at that point in time.

So my take is that it's very unlikely to occur in any case, probably a poor mobile with a 'dirty' or faulty RF output, a faulty or especially susceptible Tx, and also very unlikely to occur when the separation is greater than a metre.

So it can happen, is it really that important to have your mobile in your pocket at all times?

Ducks back under stone...

Sizzling

When at indoor meetings do people follow the same rule of not having a mobile on them, do they leave it in the car? Most indoor venues I understand cause greater potently for RF issues due to the metal structures, florescent lighting and other sources of RF that you wouldn't find down your field. There is probably a greater density of people with phones in a small place at these meets too.

I have never witnessed any memory issues with any TX's at any indoor meet I have ever been too. From this I take it that while it might be possible in theory to cause problems, the actuality is it is very rare. Surely this is part of the CE testing our phones and TX's go through  $%&