|
I have about 5 years of experience designing cell phones, about 10 years ago. I have always been concerned with cell phones and electronics for reasons other than my job. I build loud guitar amps!
Cell phones operate on several different non compatible standards called "MA's". MA stands for multiple access, a means for several simultaneous conversations on a single radio channel. Most 3G and 4G (3rd and 4th generation technology) MA's use continuous transmission, the radio transmitter runs continuously all the time the phone is sending data.
Some 2G and 3G MA's use TDMA (Time Division Multiple Access) to allow multiple access. The voice is digitized and the data is packetized. The base station will allow the phone to use one or more time slots on a given radio channel, which is divided up into small parcels of time that are dynamically assigned to each concurrent user. The radio transmitter is switched on during its time slot and off during the transmit time for other users at a rate from 16 to 66 mS depending on the MA.
Phones using this pulsed transmission mode are the ones most likely to cause interference with electronic devices, and the fast rising RF edges are what you hear in your cheap PC speakers. The usual offenders are GSM, iDEN, EDGE, and variants of these, since they all use TDMA. GSM is the most popular MA in the world, but all of these MA are slowly being replaced with 3G and 4G systems.
I admit to having fun in some of the big box electronics and music stores by taking a phone, cranking its RF power up to max and going into the home theater room or the hands on guitar amp room. Some electronics are succeptable to RF from cell phones, and some isn't. The low priced stuff like cheap PC speakers are usually bad, but there are some surprises. A $7000 Yamaha digital grand piano went absolutely bonkers whenever I got within a few feet of it.
When cars started getting "drive by wire" throttle control I was skeptical, but I have been unable to cause any anomalies in several cars even when a "worse case" phone was placed on the "brain box" or ran all over the sensors and actuators under the hood.
It is possible that the phone caused the anomalies that you observed, but there would likely be a secondary cause. Usually it is caused by a repair tech not reinstalling all the shielding, and grounding features originally installed in the car.
I built a hot rod Dodge back in the 80's, installing a turbo charged engine using early (1984) digital engine control into a car that was originally carbureted. I left out a lot of stuff I didn't absolutely need and made my own wiring harness from scratch. Yes, it was possible to stall that car with an iDEN phone next to the unshielded brain box board.
__________________
Too much power is almost enough! Turn it up till it explodes - then back up just a little.
|
Cell phone interference w/ car computer?
