RF interference from piezo loadspeakers?

[stegla]

There now seems compelling evidence that mobile phones will interfere with computer transmitters.

The latest occurance only manifested itself when the mobile actually started ringing............The LCD screen started to madly scroll through menus.

My hypothesis is this.............The peizo sounder generates RF that is picked up by the micro circuits in the tranny and corrupts the data?

The logic side of these TX's are not screened at all.

The fact that mobile-phones are radio devices was a red-herring and people have been looking for problems from the 900 and 1800 Mhz frequencies.



Any opinions?


Steve

[MattLarson29]

I know that when my phone (nextel) starts to ring, it is also transmitting back to the system that it has received the call. So it might well be that the speaker has nothign to do with the RFI, just that the phone is actively transmitting.

Matt

[stegla]

Mobiles, when switched on, are continuously talking to the network even when seemingly doing nothing.
So I would expect trouble all the time if the problem had something to do with the phone system RF transmission?

Why is it problems only occur when it makes a noise from the ringer?

Steve

[RMihara]

Wild guess here but you've got the C-Phone in one hand, TX in the other and you're capacitively coupling the C-phones signal into your TX!

Roger

[vintage1]

Originally posted by stegla
Mobiles, when switched on, are continuously talking to the network even when seemingly doing nothing.


So I would expect trouble all the time if the problem had something to do with the phone system RF transmission?

Why is it problems only occur when it makes a noise from the ringer?

Steve

Mobile phones do not talk to the transmitter all the time. They talk only when they are talked to, and when they lose signal - when they transmit around to try and pick up a local transmitter and 'register' themselves. They also talk occasionally just to let the tx know they are there...

What you saw is high power TX energy freaking out the logic circuits in your RC gear - chances are you were a LONG way from the cellphone TX and your cellphone turned the power up to max, and it was close to the RC transmitter as well.

I am trying to collect interference stories, so I would love to know what band your cellphone was on, and what make of R/C transmirtter you were using and how close the two were when the problem occurred.

BTW if you leave your cellphone near any radio, you can hear it burp when a call comes in, and occasionally at other times..

[bipeflyer]

I know at model flying meetings in the U.K. some of the bigger meetings are asking people on the flightline to switch off their phones,as they have been known to delete all of the computer memories in some radios,I don't think the manufacture was an issue, this was a blanket ban.
Nasty if you consider a 200mph turbine model losing it's TX memory in flight.....

Matt.

[vintage1]

There is enough anecdotal evidence to suggest that cellphones in close proximity to TX's - even TX's that are not ON - can wipe the TX memories.

Typically less than a foot in all cases I have heard about.

Cases I can remember are

- tx and mobile phone in flightbox on teh way to the field

- Cellphone in breast pocket while holding TX and flying...yuk!

- this case.


Its not guaranteed to happen and its probably only oine or two makes of TX that suffer from it, and then only when the cellphone is operating at maximum power - i.e. weak signal.

However its enough to make one very careful.

Leave the cellphone in the car!