RunRyder RC Helicopter Topic - Mobile Phone and Synth TX warning

RR Rated M For Mature

HOME rrTV-PHOTO GALLERIES MY GALLERY HELP-FAQ

myHOME PM pmRR MEMBERS 625 ONLINE 20 EVENTS SEARCH REGISTER START HERE

3 pages [ << < 1 ( 2 ) 3 NEXT >> ]

12643 views

POST REPLY

Ron’s HeliProz South	.	MTA Hobbies	.	Model Rectifier Corp
	.		.

Main Discussion > Mobile Phone and Synth TX warning

Pipeous
Veteran
Location: Surrey, BC, Canada

My Posts This: Topic Forum

my cel phone contract ended a year ago this January. I never got another and just cancelled. I hate cel phones. you can still dial 911 with a disconnected cel too so mine is just a phone book and 911 caller now.
I was going to take my electrics to work but hmm I have to carry a cel. is it worth the risk? not for me. leave the cel away from pit areas. we have no signal at our race track so it's all good. field is on the other side of the trees and same thing. cels don't work. that appears to be a good thing.

sad for the loss there Dennis, nice looking bird it was.

12-26-2004 Over year old.

PROFILE PM EMAIL POSTS BUDDY IGNORE HOMEPAGE GALLERY

Super Phreek
Veteran
Location: Sunny Lancaster, California

My Posts This: Topic Forum

If you would like to find out how much interference a cell phone produces, place next to some speakers, or while using it stick it close to your car radio. It gets worst as the distance increases from a cell tower, or right before it rings.

I leave mine in the car, couple times I forgot about it; scared the hell out of me, no lock-out though.

Derek

If you're not flying low; you're not flying

12-26-2004 Over year old.

PROFILE PM EMAIL POSTS BUDDY IGNORE GALLERY

Sealerman
Veteran
Location: Long Island, New York.

My Posts This: Topic Forum

Where I fly there is a cell tower and I mean a big 1 maybe a 1/4 mile away, I've seen a plank hit it once. We have never had a problem from it. I have heard of problems if there is a lose wire in any transmitting device that you can get a stray signal. Could it be a problem with your cell phone? Just an idea.

12-26-2004 Over year old.

PROFILE PM EMAIL POSTS BUDDY IGNORE GALLERY

ShempHoward
Key Veteran
Location: San Francisco, Ca - too many beggars + bad drivers

My Posts This: Topic Forum

This problem has been discussed numerous times both here and on other sites yet there are those who completely disregard this problem as an "old wives tail". Several years ago Pete Waters documented the problem in RC Report Magazine. Since then I will not fly near anybody carrying a cell phone. Keep cell phones off the flightline and away from any Tx that may need to be turned on as there is evidence that programmed settings in the computer radios can be altered by cell phones leaving you with perhaps reversed ailerons or worse.

12-26-2004 Over year old.

PROFILE PM EMAIL POSTS BUDDY IGNORE GALLERY

kirrajas
Senior Heliman
Location: DALLAS

My Posts This: Topic Forum

hmm

bottom line i feel radio manufactures should keep up with times and find a way around it.I have all JR stuff and people have said "'oh on this field JR gets hit a lot".I trust that JR makes the best stuff in the hobby and soo far i have no problems what so ever.

12-26-2004 Over year old.

PROFILE PM EMAIL POSTS BUDDY IGNORE GALLERY

kaltman
Senior Heliman
Location: Norway

My Posts This: Topic Forum

I have seen plenty helies and planes go down when due to one thing!!!!!
And that thing is MULTIPLEX

I hate them

I realy miss Kalt Helies

12-26-2004 Over year old.

PROFILE PM EMAIL POSTS BUDDY IGNORE GALLERY

oldfart
Elite Veteran
Location: Vancouver, Canada

My Posts This: Topic Forum

Food for Thought

Note that many of these reports are on "overseas" frequencies, not the frequencies we use in North America.

Here we use 72 mhz, there they will use 35 or 40 mhz. Their cell companies may also use different frequencies then we do. I am sure these differences will have some bearing on this discussion.

Phil

12-26-2004 Over year old.

PROFILE PM EMAIL POSTS BUDDY IGNORE

BigChopper
Key Veteran
Location: Cambridge, UK

My Posts This: Topic Forum

It has nothing to do with the transmission frequency of the phone. It is because a phone uses time slot allocations to share a single frequency for their calls.. Every time the phone turns on (i.e. physically transmitts a signal) in its allocated timeslot, the 'switch' transient is the part which causes the interference to the electronics in your transmitter. (This is also what is heard when you put your phone near your car radio)

Synthesized transmitters are more vulnerable to this interference due to the way the RF section is designed. A synthesiser has high impedance parts in the closed loop tuning circuit which is less tolerance to external interference.. (nothing that better design shouldn't cure).. A crystal based system is slightly different here as they do not have this high impedance section in the oscillator circuit.

The level of interference caused to your transmitter is also a function of how far away your handset is from the nearest basestation. The handset will increase its power output as the signal loss increases to the basestation.. Thus causing more interference for your TX.

There are many variables involved as to whether one TX may be better than another, so simply by saying that X is crap and Y is OK is very subjective and incorrect without calibrated power levels being used. Many of the variables are caused by the phone system itself,due to the varying output levels being transmitted by the phone in any one instance.

But yes, the manufacturers should be working towards sorting it out, it is possible.. but perhaps not within their development budget... as with a lot of consumer products.!!!

I would imagine it would be difficult to fly close enough to a base station mast for the signal level entering your aircraft electronics to be high enough to give problems... Base stations also have different signal switching characteristics to handsets... They do not switch like handset, and although they are of a higher power output than a phone... you'll still have to get pretty close to it to break through your receiver... it's more likely you'll crash into the mast instead!!

12-26-2004 Over year old.

PROFILE PM EMAIL POSTS BUDDY IGNORE HOMEPAGE

Methodical
Heliman
Location: Fairbanks, Alaska

My Posts This: Topic Forum

Ding ding ding!

Also, I know a few things about cellular technologies.

I'd bet a broomstick that this will not happen with a CDMA phone.

What happens is like so, assuming some of you have TDMA, analog, or GSM phones.

once a while the cell system will "ping" for your handset, and your handset will ping back. This typically isn't at max-power, but it could cause a very short-term glitch if your on top of the game. If you receive a call, your jacked though.

Once a incoming phone comes in over the paging channel, a TDMA/GSM handset will output at max power (2 watts?) saying "im here! im here!"... then the cell tower comes back and says 'start ringing"... your phone sends back "im ringing!"... etc etc. One the call starts the handset will throttle down the amount of power being output.

high power narrow-band transmissions are bad news all around. If your phone has ever gone off near a set of speakers, you know what im talking about.

CDMA uses low-power spread spectrum. There are many advantages of this, but one of the biggest is that it causes a significantly lower amount of out of band interference, even at max power.

TDMA is being phased out, and the next versions of GSM will use spread spectrum. So thats good news for the future.

12-27-2004 Over year old.

PROFILE PM EMAIL POSTS BUDDY IGNORE

cootertwo
Senior Heliman
Location: Labelle Florida USA

My Posts This: Topic Forum

Same stuff that's already been hashed here before. My statement is:
If some of you idiots can't live without a damned cell phone straped on your backside, you should not be in this hobby, or any other hobby for that matter. You are certainly too important to have any liesure time to yourself. The world depends on you, so please don't ever go anywhere without your presious cell phone. And for those people that find a ringing cell phone disturbing, I'm working on an anal probe that can be inserted, and will give a slight shock, when ever the user has an incoming call.
I know when I'm at the flying field, or a restuarant, or a movie theater, the constant ringing of cell phones in the back ground, gives me great peace of mind, knowing that everybody else is on top of things, and totally imformed of the worlds problems, thus making this a safer place to live.
I'll post a link to my anal probes when they go into production.

One Day At A Time

12-27-2004 Over year old.

PROFILE PM EMAIL POSTS BUDDY IGNORE GALLERY

BigChopper
Key Veteran
Location: Cambridge, UK

My Posts This: Topic Forum

Methodical,

Yes you could be right on the CDMA phones.. I was talking more GSM phones as this is where my main experience lies.. My CDMA experience is more in digital broadcasting.

Having said that, CDMA phone transmissions must also power up and down to save batter power (?) so I reckon there is still potential problems with these??.. perhaps not as likely though..

As cootertwo says, it really isn't necessary to have the phone strapped to your belt... and you shouldn't really take next to someone who is flying at the time, just in case.

Personally I cannot see a problem with just leaving your phone in your toolbox (keeping a little distance to yours and other peoples TX's), which is generally what I do.

12-27-2004 Over year old.

PROFILE PM EMAIL POSTS BUDDY IGNORE HOMEPAGE

Methodical
Heliman
Location: Fairbanks, Alaska

My Posts This: Topic Forum

sounds right to me. by no means I'm not an expert in RF. I work at a television station and hang out too much with the engineer.

IMO, its not the modulation method really, but the power output concentrated in a narrow band. Your information about the difference of a synthesized TX module makes me wonder if the interference is just the synth circuitry inducting the cellphones emitted RF power and basically getting scrambled.

the TDMA timeslotting probably doesnt help either. what is the TDMA timeslotting anyway... 1/4 or 1/8? how narrow is the channel...20khz..i dont remember? its basically a lot to cram into a tiny little timeslot and frequency.

CDMA uses lower power and spreads out over almost all of the 1.25mhz bandwidth allotted...

gsm uses a wider tdma channel for better voice clarity.... but when I think about it, its all about the paging channel and the tdma/gsm phones "response" to any request from a tower, before the call gets started... because they dont interfere after the call has started (that I know of?)

eh, im tired. time for sleep.

12-27-2004 Over year old.

PROFILE PM EMAIL POSTS BUDDY IGNORE

oldfart
Elite Veteran
Location: Vancouver, Canada

My Posts This: Topic Forum

Bigchopper/Methodical

Thank you for the good info.

Phil

12-27-2004 Over year old.

PROFILE PM EMAIL POSTS BUDDY IGNORE

HeliDoc44
Heliman
Location: Hampshire

My Posts This: Topic Forum

I think some of the "idiots" (cootertwo) are missing the real uncontrollable problem here

If someboby walks up to you while you are flying, especially if it's a public site e.g. gliding slop, they could shoot you down if they have a mobile phone in their pocket next to your TX

The radio manufacturers need to sort their products out or take them of the market. Multiplex EVOs appear to be OK with the standard crystal module... but the Synth module is affected by mobile phones...SO, either fix the problem or stop selling the Synth module

When will the radio manufacturers listen??.... When it makes head line news because someone has been seiously hurt or worse!!

12-27-2004 Over year old.

PROFILE PM EMAIL POSTS BUDDY IGNORE

BigChopper
Key Veteran
Location: Cambridge, UK

My Posts This: Topic Forum

Now you're testing me on timeslots.. To be honest, during a fast track phone developments all of the GSM protocols are now just built into the chipset and software stacks! I'd have to look at my notes to recall

There are 8 timeslots per carrier frequency.. errrr.. how much time per slot.. its something like 4 or 6ms? errr Each channel carries around 14kbps... Tell you the truth I really cannot remember off the top of my head.

I do not do so much GSM stuff these days as I'm now working on DAB Digital Audio Broadcast. This is a CDMA system (COFDM) such as digital television (DVB-T, DVB-H), but is not used in the US.

My personal feeling is that the modulation of the signal is not the important factor, it is more to do with the fast ramping of the power amplifiers so that the phone transmitts within in its short timeslot.. I believe this may also exist in CDMA when the phone switches to save battery power. (dont quote me on this either!)

It's this sharp turn on which I think gets rectified in the electronics of the RC transmitter... higher impedance nodes in an electronics design suffer worse from interference than low impedance nodes.. In a synthesiser circuit, the frequency is tuned using a variable capacitance diode (or 'varactor') to vary the amount of capacitance in the tuned circuit of the oscilllator which in turn varies the frequency. The capacitance is varied by changing the amount of reverse current flowing through the diode.. this is a very small amount of current, hence high impedance... Now if you imagine that the interference from your phone injects into this point, then it will only take a very small disturbance to screw it up... The result is that the synthesiser module will go out of lock (off frequency) or the RC transmission will have a wider band modulation on it which would happen to match that of the GSM timeslots! Thus the receiver would loose it and go into lockout..

In a crystal oscillator circuit, the high impedance node does not exist because there is no variable capacitance in the loop to tune the oscillator... The frequency is only selected by the resonance of the crystal..The point where the crystal is connected to the oscillator is of much lower impedance and hence less vulnerable to interference..
That said, I do not say that it will not be affected.. I just believe that is it less likely.

As I said before, it is possible to make the synth module less susceptable, mainly by slightly better circuit design, screening methods and better PCB layout....but this is probably not development time and money that maufacturers are willing to invest because there is no visible financial return on their money..... especially when you consider the amount of GSM 'wivestales' that exist (some true, most not).. It is just convenient to join the GSM bashing bandwagen.. lets face it, GSM does have a reputation for causing hassles.. but there are many many cases where this is just used as an excuse!

Sorry, this has got a little long winded! Please note that I have never actually measured any of these effects.. These are merely my thoughts based on my RF electronics design experience.

12-27-2004 Over year old.

PROFILE PM EMAIL POSTS BUDDY IGNORE HOMEPAGE

Methodical
Heliman
Location: Fairbanks, Alaska

My Posts This: Topic Forum

I get depressed whenever I think about the FCC mandating 8VSB here in the states. Its a damn shame, and could be a huge mistake for small broadcasters like the ones I work for.

DVT looked so much better. There was probably something going on behind the scenes with regards to special interests getting royalties for 8vsb....which sucks compared to dvt.

you know more than I do, I think I learned something from you, but not sure what it is.

12-27-2004 Over year old.

PROFILE PM EMAIL POSTS BUDDY IGNORE

modelspot.com
Heliman
Location:

My Posts This: Topic Forum

Synth Interference

Just to clarify the situation.

The following press-release is based on information from the (UKRCC) "United Kingdom Radio Control Council" earlier named "JRCUC" and coordinated with the BMFA.

!!! PRESS RELEASE December 2004 !!!

Modellers, your safety is our business!

Dear All,

MULTIPLEX is extremely sorry to hear in early October 2004 of the unfortunate incident involving the gas-turbine helicopter. An immediate investigation was launched to ascertain the cause.

Due to the following BMFA information ( ! ) safety issues have been called into question.

( ! ) USE OF MOBILE TELEPHONES IN PROXIMITY TO ELECTRONICALLY PROGRAMMED TRANSMITTERS

1st the UKRCC (earlier JRCUC) has reported there may by a problem associated with operating mobile telephones in the close proximity of programmable transmitters causing memories to be partly or fully erased. This problem has yet to be scientifically substantiated, however, it is generally known that RF radiation can disable or permanently damage some modern electronic devices.

Although the risk may be small, we believe it should be minimised by bringing it to the attention of members and clubs. Pending resolution, we recommend that mobile telephones are not switched on within 10 feet of any programmable transmitter. This may appear to be a overkill, but better safe than sorry. Care should be taken during pre-flight checks to ensure that all controls are operating fully and in their correct sense and to ensure that the memory has not been affected by any undetected or unknown transmission since the last flight.

2nd the UKRCC (earlier JRCUC) pointed out: The international limit for radio control RF transmissions is restricted to 100 mW, this would mean that mobile telephone transmissions could be up to 30 times more powerful.

For this reason civil aircraft, hospitals etc. request you to switch off all mobile telephones or similar electronic devices.

These are the circumstances why MULTIPLEX points out in the instruction manuals, particularly in the latest issue for the Royal evo, - "Do not operate mobile phones within 2 meters (6 ft 8") of the transmitter".
Care must also be exercised when modifying different brands of radio equipment. The essential range test procedure, as clearly stated in every MULTIPLEX instruction manual, must be carried out to avoid unnecessary problems. In extreme cases the manufacturer's warranty could be invalidated together with insurance.

Flair Products and MULTIPLEX dealers, factory sales and service department will be informed simultaneously are pleases to help answer any questions.

We always wish you safe flying, but we need your assistance to make flying even safer!

MULTIPLEX Team

Also, please note that in the original incident, mixed radio equipment was being used, it was not all Multiplex!

12-29-2004 Over year old.

PROFILE PM EMAIL POSTS BUDDY IGNORE

Dave Hollins
Senior Heliman
Location: UK

My Posts This: Topic Forum

I still think that Multiplex are covering their backsides with words in a manual and are not doing enough to make this situation safe.

The facts are:

1... I was using a EVO12 fitted with a Synth module
2... It had a Becker 3rd party aerial fitted.. When I got the TX checked by the UKRCC (after the crash) it was found that the Becker aerial radiated slightly higher power than the standard aerial!! I had also been using this aerial for several months.
3... I was using a JR receiver, I had this type of receiver fitted to several helis while using the EVO... This had nothing to do with the crash... see below
4... After the crash I proved it was caused by the use of the Synth module and a close mobile phone.

Multiplex requested that I got the radio checked. I took the radio (at my expense!!) to the UKRCC. They also had a EVO12 Synth they were using for testing. Both their EVO and mine would lose their transmission if a close mobile phone was called. The type of aerial or make of receiver has nothing to do with this problem. If the normal crystal module was fitted, it appeared unaffected by the mobile phone.

I am still pretty pis**d off with what happened and Multiplex have offered me NO compensation because they have covered their arses with a few words in a manual. However, I am more concerned that Multiplex are doing very little to make this situation safe.

The pilot using the radio can control the use of their own mobile phone, BUT if someone walks up to them while they are flying and they have a mobile phone then the model aircraft could go out of control.

WHY does Multiplex need "OUR assistance to make flying even safer!"
What crap
If Multiplex took the Synthersizer module off the market then flying would instantly be safer!!!!!!!!!!

This situation could result in somebody been injured or ******, if this happened will a few words in a manual be enough????

12-29-2004 Over year old.

PROFILE PM EMAIL POSTS BUDDY IGNORE GALLERY

Dave Hollins
Senior Heliman
Location: UK

My Posts This: Topic Forum

Why is it taking so much for you guys to see the real safety problem here

I say it again....

if someone walks up to a pilot who is using an EVO with synthersizer while they are flying and that someone has a mobile phone then the model aircraft could go out of control.

How do you control this situation some where like Westbury White Horse Slope

(public land)

OK.. I forgot to leave my phone in the car at Charmouth, But if somebody stood next to me with a mobile phone and the Cobra had crashed, who's fault would it have been then

your other points are:.....

"And as modelspot says it is also in the manual." This is crap to, because the warning is not in my manual... they added it to newer manuals because they knew they had a problem.

"When equipment is sold in the UK it has to be CE marked. Part of this would be emmissions testing. Basically it says that it will not emitt radiation in a way it shouldn't and it will not be serseptable to raditation of a certain level either."... Not sure why the EVO synth has a CE mark then!!!

"You don't fly near power lines because you might get interferance. Same goes for mobile phones."... you can see the power lines... they won't walk upto you and stand next to you!!!

"The situation you give about others mobile phones. They should be following BMFA rules too. If you crashed due to their mobile phone I would think their BMFA insurance would cover the costs.".... see above, public land!!! Does this also mean that everyone that attends a fly-in or flying site has to have BMFA insurance?

"Lastly, If you were using an MPX IPD rx rather than the std PPM one fitted with a failsafe. it may not have been as bad, as the controls would have just frozen, and if it had gone on long enough, gone to their preset positions. Rather than glitching like you had.".... again you don't know what you are talking about, I didn't get glitching..the controls went to full travel and it does the same with IPD... I tested it!!! the IPD did not go into fail safe!

My replacement turbine Cobra is nearly finished and my new (non Multiplex) radio is very good.

I am not pursuing this matter any further, I've just put it down to experience. However, it does piss me off when poeple make comments like: "Also, please note that in the original incident, mixed radio equipment was being used, it was not all Multiplex!" This is crap because the whole situation is caused by the Synth module / mobile phone and nothing else, what ever make, in the radio system.

I just hope nobody gets hurt in the future due to a silmilar situation, because nothing has changed except a few more warnings which "hopefully" everyone will read!! including 'joe public'

12-29-2004 Over year old.

PROFILE PM EMAIL POSTS BUDDY IGNORE GALLERY

Naomi
Elite Veteran
Location: Ontario, Canada

My Posts This: Topic Forum

JMHO, I won't use synthesize module at all, non synthesized module has no mobile phone interference at all, other than interferring by those who has the same frequency.

Naomi

12-29-2004 Over year old.

PROFILE PM EMAIL POSTS BUDDY IGNORE HOMEPAGE GALLERY

3 pages [ << < 1 ( 2 ) 3 NEXT >> ]

12643 views

POST REPLY

ReadyHeli	.	Power Helis	.	CANOMOD
	.		.

Main Discussion > Mobile Phone and Synth TX warning

Print TOPIC

Advertisers

Subscribe to This Topic