Wednesday, 28 March 2012

Smart meters.

I was chatting to someone the other day and they were worrying about Smart meters. These are utility meters that can communicate their readings via the mobile phone network to the utility companies to allow them to read your gas & electric meters without sending a meter reader or getting you to do it & submit the readings on their web site.

They'd been surfing the internet and had found sites warning about cancer & other health problems caused by the RF radiation from Smart meters. These sites are creating fear, uncertainty & doubt in order to sell solutions to problems that don't exist. Oh dear!

Warning! Radio Frequency (RF) engineering stuff:-

See the graph below?

The horizontal axis is incorrectly labelled. Distance (d) is in metres (m), not kilometres (km).

I was an RF design engineer for 29 years & measured 30MHz to 108MHz attenuation at a separation of 1 metre for various antenna matching unit designs. It was around 10dB to 15dB. See my CV.

The vertical axis is path attenuation (loss) in decibels (dB).

Decibels 101: Power loss in dB = 10 * LOG10(power loss as a fraction).

A power loss of 90% i.e. down to one tenth = 10dB. One hundredth = 20dB. One thousandth = 30dB. One millionth = 60dB. One million millionth = 120dB. One half = 3dB. One quarter = 6dB. One eighth = 9dB.

Smart meters transmit at frequencies from 900MHz (Vodafone & O2) to 1.8GHz  & 1.9GHz (Orange & T-mobile etc). People don't seem to mind having mobile phones (~2W peak RF power output when a call is in progress) glued to their ears for long periods of time.

If you stand 4 metres away (at the end of someone's garden path, say) from a Smart meter fitted to their house & operating at 900MHz, there's a path loss of 29dB. The RF energy reaching you is 1/800th of that emitted by the meter. Also, the meter doesn't produce RF energy all of the time. The duty cycle is 1% to 5% i.e. RF energy is only produced for 1/100th to 1/20th of the time.

In conclusion, even if you stand with your nose touching the window of a Smart meter (which would be silly), you get less RF radiation (RF radiation is Transverse Electromagnetic Radiation a.k.a. radio waves and not ionising radiation a.k.a. what radioactive materials emit) than what you get from your mobile phone.

Are you feeling reassured?


praguestepchild said...

I remember way back when mobile phones were new (and SCARY), some guy said that he heard that two mobile phones could cook an egg between them and actually got an egg from the bar and tried the experiment while we were sitting at the pub. I tried to bet him that it wouldn't work at all because I understood something about attenuation and ionizing radiation having specialized in e-mag, but he wouldn't bet me, the bastard.

Mind you, this was the same guy who thought the Matrix was amazing because of the science. Humans as batteries? Entropy? *sigh*

Nigel Kinbrum said...

I've managed to log-in to Blogger on my Blackberry. There's so much BS on the internet that it's nice to be able to blog on a subject that I have formal qualifications and extensive experience in.

LeonRover said...

This shit has been around for decades

First, microwave ovens, then mobile fones, now smarts.

Did a course in waveguides & stuff as part of my B Sc in Physics (not physic as M D I ain't).

But none of these f***-ups believe us when we tell 'em.

Hesoos wept.

Nigel Kinbrum said...

I published your posts and my 1st reply on my Blackberry. I'm home now, so I'm typing this reply on my lap-top.

I'm running this blog to reassure people as well as educate them. Knowledge is power an' all that.

I can't believe how much pseudo-scientific bull-crap there is on fear-mongering sites. I kept giving myself a face-palm. Jebus!

I hope that my post was suitably reassuring and educational. At the very least, everybody who's read this now knows what dB means!

Sanjeev said...

> shit has been around for decades

so depressingly true ... I studied this issue a couple of years ago.

When tested with live and dead wires, dyed in the wool "electromagnetic sufferers" can't tell which is which.

They only get symptoms when they think the wire is live (or the radio is emitting), whether it's live or not.

Nigel Kinbrum said...

Nocebo effect For The Win.

Unknown said...

Pfft. You sceptics don't know what you're talkin' about.

Just yesterday, the evil government of Lizard People remotely communicated with my laptop through bluetooth, wifi, AND good ol' infra-red. The laptop upon receiving evil commie instructions, proceeded to take an attempt on my life.

Stupid machine.

"Humans as batteries?"