BPR-1 — General Rules
Address of the Departmental Headquarters
Broadcast, Coordination, and Planning
Innovation, Science and Economic Development Canada
235 Queen Street
Addresses of Regional Offices
Refer to Radiocommunication Information Circular 66 (RIC-66) for the addresses of Innovation, Science and Economic Development Canada’s regional and district offices. This document is available on the Department’s website at: http://www.ic.gc.ca/eic/site/smt-gst.nsf/eng/sf01742.html.
Description of Regional Boundaries
- Western Region: Alberta, Saskatchewan, Manitoba, the Northwest Territories, Nunavut, British Columbia, and the Yukon
- Quebec Region: Quebec
- Atlantic and Ontario Region: New Brunswick, Nova Scotia, Prince Edward Island, Newfoundland and Labrador, and Ontario
Annex B – Method to Evaluate Compliance with the Limits of Human Exposure to Radiofrequency Electromagnetic Energy for AM Broadcasting Undertakings
This Annex provides a two-step methodology to evaluate Safety Code 6 compliance distances for AM broadcasting undertakings.
Since compliance distance will likely be in the near-field region of AM transmitting antennas, both the electric field (E-Field) and the magnetic field (H-Field) need to be considered. The evaluation of compliance distance is performed in two steps, as follows.
Step 1: Determining the applicable field-strength limits
The first step consists of determining nerve stimulation-based (NS) and specific absorption rate-based (SAR) reference levels for both the electric field and the magnetic field for the AM site of interest. These limits are provided in the Safety Code 6 document – Limits of Human Exposure to Radiofrequency Electromagnetic Energy in the Frequency Range from 3 kHz to 300 GHz. When evaluating the 50% of Safety Code 6 limits, the Safety Code 6 NS-based limit shall be multiplied by a factor of 0.5, while the Safety Code 6 SAR-based limit shall be multiplied by a factor of 0.71.
The most stringent field strength limit (the lower field strength limit) between the nerve stimulation (NS) limit and the specific absorption rate (SAR) limit shall be used.
Step 2: Calculating the theoretical compliance distances
Tables B1-B9 provide the electric and magnetic field-strength levels at various distances from the base of AM broadcasting towers for a number of frequency and tower electrical lengths. Since the tables are normalized to a radiated power of 1 kW for an AM single tower, the field-strength limits evaluated in Step 1 need to be adjusted for the actual nominal station power. In the case of tower arrays, the radiated power of each tower can be used to adjust the field limits if they are known. Otherwise, a conservative prediction is to be made by assuming all transmitted power is radiated from each antenna. In such a case, the appropriate value from the tables could be used to define the zone of minimum compliance distance around the array, consisting of circles with appropriate radii, each of which are centered around a tower in the array.
In the case of a shared AM transmission tower broadcasting on multiple frequencies, a minimum compliance distance should be calculated for each frequency using the method described in this Annex, and assuming that the radiated power is the sum of the powers of all stations transmitted by the tower. The largest calculated minimum compliance distance should be selected as the overall minimum compliance distance for the tower.
The following formulas shall be used to adjust field strength levels based on applicable limits determined in Step 1:
Once the adjusted field limits are calculated, the Tables B1-B9 provide the theoretical compliance distances for various frequencies and electrical antenna heights in degrees (360° = 1 wavelength). For electrical or magnetic field values that fall in between the data points in the tables provided, the first data point with an electrical or magnetic field value below the target value for compliance should be selected.
Note 1: Electrical antenna height (in degrees) is calculated using the following formula:
Tables B1-B9 can be used directly to evaluate the electric and magnetic fields for facilities that use:
- electrical height within 1% wavelength (i.e., within 3.6 electrical degrees) of the electrical height for the given table, and
- carrier frequency at the frequency or the adjacent channel frequency for the given Table.
For antennas that do not correspond to the above conditions, the electrical and magnetic fields will be evaluated as follows:
- For electrical field, available Tables using the next higher and lower frequency, and next higher and lower electrical length, shall be consulted (4 readings). The largest distance reading shall be retained as the compliant distance for electrical field.
- Separately for the magnetic field, the available tables using the next higher and lower frequency, and next higher and lower electrical length, shall be consulted (4 readings). The largest distance reading shall be retained as the compliant distance for magnetic field.
The Safety Code 6 compliance distance shall be determined as the largest distance among the two distances retained for the electrical and magnetic fields. The compliance distance as determined using this method is referenced to the surface of the tower, and cannot be less than 2 metres.
Tables of Distance from Tower vs. Adjusted Electric and Magnetic Field Strength
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