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RF Exposure Audits. EDDIE BULL Baldock Operations Manager Fixed and Mobile Monitoring and Measurements Section Radiocommunications Agency. The Stewart Report:

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rf exposure audits
RF Exposure Audits

EDDIE BULL

Baldock Operations

Manager

Fixed and Mobile Monitoring and Measurements Section

Radiocommunications Agency

slide2
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.

slide3
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.

slide5

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
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.
calculations1
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.
slide8

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

slide11

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)

slide12

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.