Update: Aerials on lightposts

[mogga]

Some data: (And no mention of dimming them)

1. The antennae is used to control the street light from a central system. Ie switch it on or off and report on its status. 2. Please see the table below for the requested values

+----------------------------------------------------------------------+ |Measurement |Value | |------------------------------------------------+---------------------| |Frequency (Hertz) |868MHz | |------------------------------------------------+---------------------| |Wavelength (metre) |0.35m | |------------------------------------------------+---------------------| |Electrical field strength (volt per metre) |23.61V/m | |------------------------------------------------+---------------------| |Magnetic field density (ampere per metre) |6.282e-2A/m | |------------------------------------------------+---------------------| |Magnetic flux density (tesla) |7.909e-8T | |------------------------------------------------+---------------------| |Power flux density (watt per square metre) |1.479W/m^2 |

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1. There are no statutory exposure limits in the UK. The limits that apply do so as a matter of Government policy (see [1] As detailed on the website, the public exposure limits are 360 µT for magnetic and

9 kV/m for electric (both of which we adhere to quite comfortably) where the time of exposure is significant.

[Graham.]

Presumably in response to a communication with your local authority.

Did you specifically ask about RF exposure, or are they just assuming that you are a Tin-foil Hatter?

[Robin]

I may be suffering the effects of 20+ years of phoning Virgin Media/Telewest/Cable London (see Stuart Noble's advice to TMH re "Sorry!") but don't we need to know *where* those values are measured? Eg on the pavement below one light? At the top of the pole, 300mm from aerial when attaching policemen's helmet to it?

[Brian Gaff]

I will have to get my scanner on the case then... Brian

[Andrew Gabriel]

They've replaced all the streetlamps around me for about a 4 mile radius, except the 3 in my road :-)

These new lamps were going to be on a radio system, but at the moment they all have standard NEMA photocells on top. Maybe they'll be swapped out later for radio switches.

The lamps are dimmable, but that's preset as they were installed, and I don't think it will be remote controlled. In some side roads, they've been set very dim. One which also has a Give Way sign attached to the column, you can see the sign illumination is giving off more light than the lantern on the top of the column.

The new ones are mostly all fluorescent tubes, with HID lamps used on the more major roads (HPS on some, and new white HID on high street).

In my road, still got 3 LPS orange lamps. They are however somewhat brighter than those new fluorescents which have been dimmed right down.

As always, seemed like a waste of money. Over the past 10 years, most of the concrete columns had been replaced, which meant that most of the columns were not very old. Nevertheless, all the columns were pulled out, and new ones fitted, except in one road which was done about 5 years ago, and they just replaced the SON lanterns with fluorescent lanterns on the existing newish columns.

[mogga]

Indeed.

Nothing to stop me asking some more questions though :)

If they transmit in a mesh rather than individually to a central point then they only have to reach the next lamp.

[tony sayer]

In article , Graham. scribeth thus

That above is virtually meaningless presented like that...

[mogga]

Which bit? The table?

[tony sayer]

In article , mogga scribeth thus

Eh?, 9 kV metre?...

The quoted field strength where is it to be measured from and/or at...

[DerbyBorn]

tony sayer wrote in news: [e-mail]:

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amazing that we have technology in our midst that we know nothing about. This would not have been the case many years ago.

I once contacted the appropriate dept at our council when aerials appeared on some traffic lights and got a very comprehensive reply.

[Robin]

Isn't V/m the relevant SI unit making kV/m OK?

agreed (as I noted y/day)

[Matty F]

Some years ago I learned that weather information in New Zealand is transmitted using meteor burst communications, i.e. radio reflected off meteor trails.

[tony sayer]

In article , Robin scribeth thus

Usually referred to "x" dB above 1 Microvolt per metre in radio Eng..

But that level is a "tad optimistic" for the 868 MHz licence exempt band;!...

[Dave Liquorice]

I think "eh?." is in response to that being what they quote as the maximum exposure level to an electric field. It equates to around 18 kV head to toe, doesn't sound very nice to me...

[Robin]

Thanks (and to Tony too). I u/s now where Tony was coming from. I think the council may have some defence though IIRC that V/m is used for safety limits.

[mogga]

uh? Should my brain be melting already?

[tony sayer]

In article , mogga scribeth thus

I'm getting a bit hard pressed to think were we could find that level perhaps the highest powered radar set around. A one Meg Broadcast TX up very close and personal but a lamp standard .. nah;(...

[Andy Wade]

If that's from emfs.info it'll be for 50 Hz, not for RF fields at UHF. And that's free-space field strength. If you're standing under a HV power line you won't get 18 kV head to toe because your body is a good conductor relative to the air-gap between your head and the line above.

For RF exposure you need to look at the ICNIRP guidelines

Simple E and H field strength limits are only used at very low frequencies. At UHF the exposure limits are defined in terms of absorbed power, IIRC.