Do modern mobile phones put out a weaker signal?

03 April 2011

Question

Hi Dr Chris ,
I was listening to one of the "up all night" or dr karl podcasts that you were hosting and a user was asking why do we turn off mobile phones in hospitals and airplanes.
I have a story that may explain why this was necessary , but I assume that todays phones dont output the same levels of power.
Back about 18 years ago , I was commissioned to install and upgrade Dimms inside of the equivalent of EftPos machines for a bank in Western Australia. This involved going out on site country locations , replacing the Dimm with a new dim and ringing the technical support centre to program it up and get it going .
Unfortunately we had what seemed to be a large quantity of faulty dimms , I would ring into the tech support to enable the new chips and they would fail , but when the chips went back they were perfect and worked fine on the benchtops.
We eventually worked out that the Motorola Dynatac that I was using was causing enough interference so that the "hardwired"(they used physical POTS phone lines) eftpos machine failed when it was communicating back to the central techs .
Also any person that was on a mobile phone call ( luckily they weren't so popular back then) would cause the eftpos machine to fail while it was in transaction back to the bank.
So .. yes I can see why they would not have wanted mobile phones being used in hospitals and or planes back then. But I assume todays phones put out a much weaker signal .
P.S. This was back in the analogue days when the range of the mobile phone towers was so much greater because of the higher strength I assume

Carl
Perth , Western Australia.

Answer

We put this question to Professor Mark Beach, University of Bristol...

Mark - Yes. The transmit power of the mobile devices is actually dropping. Although you may think your battery life is quite poor these days if you've got a smartphone, it's not to do with the RF energy coming off the phone. It's more to do with the display technology and the fancy things to do with the applications. So transmit power is going down and as I said earlier, we need to get it down in case there are any concerns on the health side, but also conserving energy and being more green.s that range.

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