intensity of radio em field

[Alain Henry]

I am planning to buy a home weather station with a remote temperature
sensor (wireless, ie using radio transmission at 433 MHz).

I am trying to figure out how the intensity of the electromagnetic
field we would have indoor caused by this radio emitter would compare to
that ambient, background, field (caused by radio and TV emitters, cell
phone relay stations, other electronic equipment, etc.). The manufacturer
does not give information on the power of the radio emitter (or on the
exposure we would get fom it).

World Health Organisation gives a typical value for background exposure to
such exposure (0,1 W/m2) to radio and TV emitters. What would be the
exposure for the radio sensor?

Thanks for any help

Alain

 

[Andrew Holme]

Alain Henry wrote:

On Sun, 19 Dec 2004 10:52:05 +0000, Andrew Holme wrote:

Alain Henry wrote:
I am planning to buy a home weather station with a remote
temperature sensor (wireless, ie using radio transmission at 433
MHz).

I am trying to figure out how the intensity of the electromagnetic
field we would have indoor caused by this radio emitter would
compare to that ambient, background, field (caused by radio and TV
emitters, cell phone relay stations, other electronic equipment,
etc.). The manufacturer does not give information on the power of
the radio emitter (or on the exposure we would get fom it).

World Health Organisation gives a typical value for background
exposure to such exposure (0,1 W/m2) to radio and TV emitters. What
would be the exposure for the radio sensor?

Thanks for any help

Alain

Those 433 MHz devices put out milliwatts. TV transmitters run
megawatts. The field strength falls off as the square of distance.
Your additional exposure will be orders of magnitude below
background.

Thanks for the info. I'd like to have accurate references and info.
Any reference I could explore?

http://www.google.co.uk/search?q=electromagnetic+field+strength+square+distance

TV Mast = 1MW
Weather station = 10mW (say)

1MW / 10mW = 100,000,000
Square root = 10,000

Therefore field strength 1 metre from weather station is equivalent to TV
mast 10km away.

 

[Rich Grise]

On Sun, 19 Dec 2004 23:20:36 +0100, Alain Henry wrote:

On Sun, 19 Dec 2004 21:51:33 +0000, Andrew Holme wrote:
Alain Henry wrote:
On Sun, 19 Dec 2004 10:52:05 +0000, Andrew Holme wrote:
Alain Henry wrote:
I am planning to buy a home weather station with a remote
temperature sensor (wireless, ie using radio transmission at 433
MHz).
Apologies, I was not clear in my previous question. I meant references to
the specs or a manufacturer of such small radio devices. I'll go
and search internet anyway. Thanks again.

Maybe you could check with whoever it was you were planning to buy the
home weather station from.

Good Luck!
Rich

 

[Andrew Holme]

Alain Henry wrote:

I am planning to buy a home weather station with a remote temperature
sensor (wireless, ie using radio transmission at 433 MHz).

I am trying to figure out how the intensity of the electromagnetic
field we would have indoor caused by this radio emitter would compare
to that ambient, background, field (caused by radio and TV emitters,
cell phone relay stations, other electronic equipment, etc.). The
manufacturer does not give information on the power of the radio
emitter (or on the exposure we would get fom it).

World Health Organisation gives a typical value for background
exposure to such exposure (0,1 W/m2) to radio and TV emitters. What
would be the exposure for the radio sensor?

Thanks for any help

Alain

Those 433 MHz devices put out milliwatts. TV transmitters run megawatts.
The field strength falls off as the square of distance. Your additional
exposure will be orders of magnitude below background.

--
Never hold a radio transmitter against the side of your head.

 

[Alain Henry]

On Sun, 19 Dec 2004 10:52:05 +0000, Andrew Holme wrote:

Alain Henry wrote:
I am planning to buy a home weather station with a remote temperature
sensor (wireless, ie using radio transmission at 433 MHz).

I am trying to figure out how the intensity of the electromagnetic
field we would have indoor caused by this radio emitter would compare
to that ambient, background, field (caused by radio and TV emitters,
cell phone relay stations, other electronic equipment, etc.). The
manufacturer does not give information on the power of the radio
emitter (or on the exposure we would get fom it).

World Health Organisation gives a typical value for background
exposure to such exposure (0,1 W/m2) to radio and TV emitters. What
would be the exposure for the radio sensor?

Thanks for any help

Alain

Those 433 MHz devices put out milliwatts. TV transmitters run megawatts.
The field strength falls off as the square of distance. Your additional
exposure will be orders of magnitude below background.

Thanks for the info. I'd like to have accurate references and info. Any
reference I could explore?

 

[Alain Henry]

On Sun, 19 Dec 2004 21:51:33 +0000, Andrew Holme wrote:

Alain Henry wrote:
On Sun, 19 Dec 2004 10:52:05 +0000, Andrew Holme wrote:

Alain Henry wrote:
I am planning to buy a home weather station with a remote
temperature sensor (wireless, ie using radio transmission at 433
MHz).

I am trying to figure out how the intensity of the electromagnetic
field we would have indoor caused by this radio emitter would
compare to that ambient, background, field (caused by radio and TV
emitters, cell phone relay stations, other electronic equipment,
etc.). The manufacturer does not give information on the power of
the radio emitter (or on the exposure we would get fom it).

World Health Organisation gives a typical value for background
exposure to such exposure (0,1 W/m2) to radio and TV emitters. What
would be the exposure for the radio sensor?

Thanks for any help

Alain

Those 433 MHz devices put out milliwatts. TV transmitters run
megawatts. The field strength falls off as the square of distance.
Your additional exposure will be orders of magnitude below
background.

Thanks for the info. I'd like to have accurate references and info.
Any reference I could explore?

http://www.google.co.uk/search?q=electromagnetic+field+strength+square+distance

TV Mast = 1MW
Weather station = 10mW (say)

1MW / 10mW = 100,000,000
Square root = 10,000

Therefore field strength 1 metre from weather station is equivalent to TV
mast 10km away.
Apologies, I was not clear in my previous question. I meant references to

the specs or a manufacturer of such small radio devices. I'll go
and search internet anyway. Thanks again.
Alain

 

[TaxSrv]

"Alain Henry" wrote:

Apologies, I was not clear in my previous question. I meant
references to
the specs or a manufacturer of such small radio devices. I'll go
and search internet anyway. Thanks again.
Alain

If you can't easily find the info, I ran the RF safety calculator on

an U. of Texas website. At 433MHz, and a distance of 20 feet from the
antenna, 1,650 watts is the threshold of a safety problem. With a
sensor broadcasting from the top of your house, no one else living
within hundreds of miles of you could operate such a device due to
interference! And it sure couldn't be battery powered....

Reg,
Fred F.