Hello Gerard,
On Saturday, 6 April 2019 09:50:36 AEST Gerard Borg wrote:
> Then the following calculation yields the maximum received upper power
> density for any type of antenna,
>
> POWER_DENSITY__WATTS_PER_SQMETER = TRANSMIT_EIRP__WATTS / (4 * pi *
> DISTANCE__METERS^2)
>
> and for...
> DISTANCE__METERS = 1 TRANSMIT_EIRP__WATTS = 4
>
> we obtain...
> POWER_DENSITY__WATTS_PER_SQMETER = 0.318
> ELECTRIC_FIELD_STRENGTH__VOLTS_PER_METER = 10.9 R.M.S.
I hadn't realised 4 watts is also the maximum EIRP permitted for WiFi in
Australia. However the radiation from a WiFi antenna is highly unlikely to be
isotropic, which could substantially increase the power density experienced in
practical cases above that figure of 0.318 watts/sq.metre.
> Having said this, actual human safety limits depend on RF carrier frequency.
When I looked at this in October 2009, the last comprehensive study by the
ICNIRP (International Commission on Non Ionizing Radiation Protection) dated
1997 came up with these limits, expressed here in watts/sq.metre:
10 to 400 MHz - 2
400 to 2,000 MHz - f/200
2 to 300 GHz - 10
The 1997 ICNIRP limit for the 2.4 GHz and 5 GHz WiFi bands is then 10
watts/sq.metre, which seems very high. However an update "Draft RF Guidelines
100 KHz - 300 GHz" as at October 2018 is in the works - see
https://www.icnirp.org/
David L.
_______________________________________________
Link mailing list
[email protected]
http://mailman.anu.edu.au/mailman/listinfo/link
