## Wednesday, 28 March 2012

### Smart meters.

I was chatting to Kerrie's mum the other day and she was worrying about Smart meters. These are utility (usually electric) meters that can communicate their readings via radio waves & the internet to the utility companies to allow them better control of their generation plant. She'd been surfing the internet and had found sites warning about cancer and other health problems caused by the radiation from Smart meters. These sites are creating fear, uncertainty and 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).

Trust me. I know what I'm talking about. I was an RF design engineer for 29 years. See my CV.

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

Decibels 101: Power loss in dB = 10 x LOG10 of the loss as a fraction.

A power loss of 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. Got it?

Smart meters transmit at frequencies from 900MHz (Vodafone & O2) to 1.9GHz (Orange & T-mobile etc). I mentioned mobile phone networks, as people don't seem to mind having mobile phones 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.

Are you feeling reassured, now? My work here is done!

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.