RF Exposure Audits

EDDIE BULLBaldock Operations

ManagerFixed and Mobile Monitoring and

Measurements Section

Radiocommunications Agency

The Stewart Report:We recommend that an independent, random, ongoing audit of all base stations be carried out to ensure that exposure guidelines are not exceeded outside the marked exclusion zone and that base stations comply with their agreed specifications. If base station emissions are found to exceed the guideline levels, or there is significant departure from the stated characteristics, then the base station should be decommissioned until compliance is demonstrated. We recommend that particular attention should be paid initially to the auditing of base stations near schools and other sensitive sites.

The following Table gives a summary of the

RF Audit progress in 2002 on Cellular Radio base station activity on or near

Schools and Hospitals.

Stewart Audit Progress 2002

Nr school Hospital 100 Total RFA sent Completed Extra 50 RFA Sent Completed Per Region

1 North East 4 2 6 6 6 1 1 1 7

2 North West 7 4 11 11 10 5 5 4 16

3 S & S West 10 5 15 15 15 7 6 6 22

4 Mid & E Anglia 7 4 11 11 11 6 5 5 17

5 London & SE 15 7 22 22 22 0 0 0 22

6 Scotland 17 1 18 18 18 27 27 27 45

7 NI & IOM 7 3 10 10 10 3 3 3 13

8 Wales 4 3 7 7 7 1 1 1 8

TOTAL 71 29 100 100 99 50 48 47 150

*TOTALS - 110 Audits completed in 2002 calender year, the 36 audits from 1 January to 31 March 2003 are carried over to 2003 audit figures

Region completed all 2002 / first phase 2003 audits

2002 audit outstanding in 2003. (School required a re-visit due to faulty aerial, school removed from audit programme as not happy to receive 2nd visit)

The final audit of first phase 2003 is due in April 2003, the school asked to delay

Regions 3 and 4 are both one below target. One school was audited in 2001 and there have been no changes at the site, an insufficent number of registrations in the other Region resulted in a shortage of one. The shortages have already been rectified with 2003 registrations

STAGE 1 STAGE 2 TOTALSRegion

•RF exposure comes from many sources, not just from cellular systems. In fairness to the cellular operators the Agency decided to carry out a number of RF Audits across the radio spectrum covering the band 30MHz to 2GHz and post the results on the RF Audit Web site.

•Residential locations close to major TV and Radio broadcast sites were chosen to compare RF levels from broadcast, paging, PBR and hobby radio sources etc with emission levels from cellular systems.

• The following slides show how the Exposure Quotient for a single emission and multiple emissions is calculated.

Calculations– Exposure Quotient. (Single Signal)

– The measurement of a single signal can be given a dimensionless quantity known as the exposure quotient. This quantity is derived by dividing the measured power density

(Smeas) by the guideline level (Sguid) for the measured frequency.

–

– An exposure less than unity indicates compliance with the guidelines.

guidS

measSQuotientExposure(1)

Calculations– Exposure Quotient. (Many Signals)– RF exposure surveys are concerned with

simultaneous exposure to many different radio signals spread throughout the radio spectrum. All signals impinging on the measurement site will contribute to the total exposure at the point of measurement. The total exposure quotient will be equal to the sum of the quotients for all signals in the measured bands.

guidN

measN

guid3

meas3

guid2

meas2

guid1

meas1

N

1iguid

i

measi

S

S.....

S

S

S

S

S

S

S

SQuotientExposureTotal)2(

•The following spectrum plot examples show RF activity in the two sub-bands 30 - 860MHz and 860MHz - 2GHz.

SANDY HEATH – Comparison of Cellular V Other Broadcasts.Extracted from Report ML2-016-02

Position 1.OS map reference TL21706 50599Antenna at Head Height.Frequency band = 30MHz – 860MHz.Band Exposure Quotient 3.46e-3

PUBLIC BROADCAST AND PMR

Frequency Fieldstrength ExposureMHz dBuV/m Quotient519.3 113.2 2.13e-4519.2 111.2 1.35e-4225.5 109.2 1.10e-4222.1 109.2 1.10e-4226.2 109.0 1.05e-4226.0 108.6 9.61e-5221.5 108.6 9.61e-5226.3 108.5 9.39e-5221.7 108.3 8.97e-5222.5 108.2 8.76e-5

Frequency band = 860MHz – 2GHz.Band Exposure Quotient 4.95e-5

CELLULAR PHONES

Frequency Fieldstrength ExposureMHz dBuV/m Quotient931.8 97.1 2.90e-6945.6 97.1 2.90e-6942.0 95.7 2.08e-6932.2 95.5 2.01e-6945.7 95.5 1.99e-6952.8 95.1 1.80e-6931.7 95.0 1.79e-61854.8 97.8 1.70e-6931.9 94.7 1.68e-6946.8 94.6 1.62e-6

SANDY HEATH – Comparison of Cellular V Other Broadcasts.Extracted from Report ML2-016-02

Summary of example plots

The total Exposure Quotient for the whole band RF emissions (30MHz – 2GHz) is 3.51e-3.

The Exposure Quotient for the sub-band 30 - 860MHz is 3.46e - 3. (1/289th of the ICNIP guidance level)

The Exposure Quotient for the sub-band 860MHz - 2GHz is 4.95e - 5. (1/20202th of the ICNIP guidance level)

Although these measurements are site specific and represent only a snapshot of the RF activity at the time of the survey, the ratio of cellular activity to other types of emissions appear to be typical at

most of the locations surveyed.

At the example location the dominant emissions were Analogue TV and T-DAB signals At most of

the other survey locations Band 2 broadcast, T-DAB and TV emissions yielded the highest levels.