Gerard Borg Gerard.Borg at anu.edu.au
Sat Apr 6 09:50:36 AEDT 2019

```Hello David et. al.

You are correct for R.M.S (root mean square electric field) which is the
usual way to express
averages.

(R.M.S. Electric Field) = (Peak Electric Field) /  sqrt(2)

My calculations follow.

Relation of power density to electric field strength (assume R.M.S
electric field) is as you say
given by

POWER_DENSITY__WATTS_PER_SQMETER =
(ELECTRIC_FIELD_STRENGTH__VOLTS_PER_METER)^2 / (120 * pi)

If...
ELECTRIC_FIELD_STRENGTH__VOLTS_PER_METER = 9 R.M.S.
then..
POWER_DENSITY__WATTS_PER_SQMETER =  0.215

We can also compute a hard exposure limit.

Consider RF transmission with 4Watt EIRP (Equivalent Isotropic Radiated
Power).
This would apply to WiFi using 2.5GHz or 5GHz and the legal emission limit.
https://www.legislation.gov.au/Details/F2014C00930/ff366b29-3c57-447d-a6e7-e15451eeee83

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.

Having said this, actual human safety limits depend on RF carrier frequency.

5G power limits will have to comply with emission standards regardless
of what antenna(s) they use.
I do not believe that this will necessarily be difficult, even if base
stations have many antennas.

As an example from 5G, consider massive MIMO - a widely studied
technology which employs hundreds of
co-located, spectrum sharing  antennas on a base station. The obvious
reason for this approach is to
improve spectral efficiency by sharing the radio spectrum simultaneously
with many mobiles. This has
led to demonstrations of spectral efficiences > 70 bits-per-second-per-Hz.

Massive MIMO also has the desirable side-effect of reducing the total
power transmitted from base
stations and mobiles compared to conventional single antenna systems
under otherwise the same conditions.

Gerard

On 4/5/19 4:41 PM, Marghanita da Cruz wrote:
> Here is ACMA on the subject
>
>> Also, the closer a small cell is to your mobile, the less power it
>> needs to communicate. The new 5G base stations will go into â€˜sleep
>> modeâ€™ when there are no active users, making their power output
>> levels even lower than current 4G base stations.
>
> https://www.acma.gov.au/Home/theACMA/a-guide-to-small-cells?utm_medium=email&utm_campaign=Engage+Issue+85+February+2019&utm_content=Engage+Issue+85+February+2019+CID_0998af901bd146f29999a70232559280&utm_source=SendEmailCampaigns&utm_term=small+cells+fact+sheet
>
>
> On 3/4/19 8:09 pm, David wrote:
>> On Wednesday, 3 April 2019 17:59:16 AEDT Stephen Rapley wrote:
>>
>>> While the health impacts of RF exposure are real a quick survey of
>>> the source of this story and the host siteâ€™s other offerings -
>>> David Icke and anti-vaxer sentiments - leaves you with the sense
>>> this site is trying to squeeze the health concerns about 5G and RF
>>> in general into a tinfoil hat that doesnâ€™t do the issue justice.
>> Yes indeed.  Linkers may remember a discussion some years ago
>> regarding a desk study by the epidemiologist  Dr. Bruce Hocking for
>> Telstra which found a doubling of childhood leukemia in the suburbs
>> around Gore Hill in Sydney.  This was to be phase-1 of a more
>> detailed study, but I understand Telstra cancelled phase-2.
>>
>> The opening paragraph of the website item -
>> https://takebackyourpower.net/brussels-first-major-city-to-halt-5g-due-to-health-effects/
>> - states "Ms. Fremault accurately identified that a *5G pilot project
>> is not compatible with Belgian radiation safety standards* (9 V/m, or
>> 95 mW/m2 according to this online converter[1])".
>>
>> But I believe the power density of an EM field of 'e' volts/metre in
>> free space is given by (e^2)/(120*Pi) watts/sq.metre.  A field of 9
>> volts/metre is then 0.215 watts/sq.metre or 215 mW/sq.metre, not 95.
>> An ABC source once told me that the field on the roof of their
>> administration building at Gore Hill was around 5 volts/metre, and I
>> think that also used to be the Russian standard for maximum weekday
>> exposure.
>>
>> So I think the story is wrong somewhere (maybe me?)....
>>
>> David L.
>>
>>
>> --------
>> [1] https://www.powerwatch.org.uk/science/unitconversion.asp
>> _______________________________________________