Cell Phone Interference

I had a flashing back on one of my older phones. It sensed any RF and flashed, thus i knew when it was transmitting..

My current motor Razr seems to run the battery down real fast at times when I enter the place where i am currently at, where there is no reception. It seems to get in some mode where it must be doing a lot of transmitting where there is no reception. Sounds dumb.

Of course teh cell phone will use full power when its in a poor location, and can't back off power like in a good location.

greg

And I can easily hear GSM phones signalling if I'm on a normal phone. Or on the car radio as the GSM phone switches between cell-sites

There's an interesting collection of real-world EMC problems at

Barry

It does, actually. Caught it yesterday, was checking if the caller ID worked and went to the TV to check that as well, it was messing up the TVs SMPS allright.

Hey, I would know that.

Would you believe I have twice opened and fixed this (cheap) TV, once it had a dried electrolythic cap which was mounted too close to a heating 7805 regulator and once I don't remember what, after a lightning which had killed the Ethernet controller (and not the coax PHY buffer...) of my Nukeman, the TV and the cable modem, got the latter replaced and the other two fixed.

But the case for the cellphone is proved now, anyway. It messes up the power supply (IIRC the one which makes the 5V stays on all the time, not sure about the others, I think the sweeps supplies were off but I am no more than 60% sure of that, lightning event was a year ago). About 30 cm (1ft) from the board is close enough, I am not sure the missus will allow me to try any closer (she keeps the phone in the other corner of the room since it got under suspicion ....:-).

Dimiter

Sounds right. When far from the tower, the tower will instruct the cell phone to increase it's output power to improve the signal. (And lower when you're in close to avoid overloading the cell site's receiver multicouplers.) So, if you're in an area of poor coverage, you have at least 2 things eating away at battery life:

Temporary signal fades, which drive the need for more frequent updates, and, High RF power ouput instructions from the cell site.

-mpm

What do you mean "it"? I've observed the effect on numerous receivers, some quite expensive (which isn't a guarantee of quality) and several quite sensitive.

As someone suggested, its probably overloading the receivers' front end or IF sections. But that qualifies as interference.

Now, picture this kind of interference mesing up a pacemaker or other medical electronics.

-- Paul Hovnanian mailto: snipped-for-privacy@Hovnanian.com

------------------------------------------------------------------ Karate is a form of martial arts in which people who have had years and years of training can, using only their hands and feet, make some of the worst movies in the history of the world. -- Dave Barry

It could also be caused by an external device overloading and generating spurious signals.