BC-16 — AM Proofs of Performance

Issue 1
June 1, 1996

Spectrum Management
Broadcasting Circular

Broadcasting Circulars are issued for the guidance of departmental staff and are complementary to Broadcasting Procedures and Rules. Although intended for internal use only, they are also available to the public. The information contained in these circulars is subject to change without notice. It is therefore suggested that interested persons consult the nearest district office of Industry Canada for additional details. While every reasonable effort has been made to ensure accuracy, no warranty is expressed or implied. As well, these circulars have no status in law. Additional copies of this or other circulars in the series are available from any office of the Department.

Comments and suggestions may be directed to the following address:

Industry Canada
Radiocommunications and Broadcasting Regulatory Branch
300 Slater Street
Ottawa, Ontario
K1A 0C8

Attention: DBC-E

Foreword

This circular supersedes the AM-1 method (2nd edition) of March 1987 on the processing of AM proofs of performance.


Purpose

This circular addresses the process to follow in evaluating AM proofs of performance. It takes into account recommendations formulated by the TAC (Technical Advisory Committee on Broadcasting) in March 1992, concerning the period required for sending notices to broadcasters for supplementary proofs of performance.


Procedure

Part 1 provides detailed information on the sending of notices to broadcasters for submission of proofs of performance. Part 2 deals with the actual processing of AM proofs of performance.



Part 1 Notice to Broadcasters for Supplementary Proofs of Performance

(sent by the Regional Offices)

1.1 Timing for the Submission of Supplementary Proofs of Performance

Supplementary proofs of performance must be submitted every five years following a final proof of performance or a previous supplementary proof of performance. They are required for directional day and night patterns but not for omnidirectional patterns.

1.2 Timing for the Sending of Reminder Notices

1.2.1 Notices reminding broadcasters to submit proofs should be sent before the end of May of the year preceding the end of the five (5) year cycle. It is highly recommended that the regional office request a written response to the reminder notice by a specified date, to ensure that the broadcaster has incorporated the proof into his/her planning process. For convenience, the reminder letters should include the form IC 2374 "Notice of Retention of Broadcasting Engineering Consultant".

1.2.2 Should the broadcaster not respond by the specified date, a second reminder notice should be sent three to five months after the first notice.

1.3 Deadline for Submission of the Supplementary Proofs of Performance

The notice to the broadcasters must state that they are to send their proof by December 1 of the year in which it is due.

1.4 Deadline Extensions

1.4.1 Broadcasters may request extra time to produce supplementary proofs. The reasons invoked include the following:

  1. undergoing a feasibility study for modification of facilities;
  2. proof measurements have identified the need to replace or repair equipment;
  3. the broadcaster wishes to coordinate proof submission for more than one of his stations for economic reasons.

1.4.2 In general, an extension of six months to one year can be given provided that station operation is adequate, that all valid complaints about interference have been resolved, and that the broadcaster has committed in writing to submit the proof by a mutually agreeable date.


Part 2 Procedure for Processing Proofs of Performance

2.1 Evaluation of Proofs - General

2.1.1 The various block diagrams for the processing of proofs appear in Broadcasting Circular 1 (BC-1), AM, FM & TV Broadcasting Process, Annex I, Part E-Proofs.

2.1.2 The requirements are provided in Broadcasting Procedures and Rules, Part II (BPR, Part II), Application Procedures and Rules for AM Broadcasting Undertakings, Sections 2.5 and 2.7 for final proofs, 2.6 and 2.8 for preliminary proofs, and 2.9 for supplementary proofs of performance.

2.2 Evaluation of Preliminary or Final On-Air Proofs

2.2.1 Assessment is done at Headquarters (HQ) as Industry Canada's reply must be made within five working days after the proof is received.

2.2.2 All copies of correspondence with the broadcaster, or his/her consultant, will be sent to the regional office once the evaluation has been completed.

2.3 Evaluation of Final Proofs of Performance

2.3.1 Request for Submission of Proofs

The request to submit a final proof will be made in the Department's reply to the broadcaster of its evaluation of the preliminary proof of performance. The final proof is to be submitted 90 days after the preliminary proof has been approved. Upon written request from the broadcaster or the retained engineering consultant, this time period can be extended based on justifiable reasons like complexity of the site and the technical arrangements made, other major works in the region that may affect the project, etc.

2.3.2 Evaluation

2.3.2.1 HQ will determine whether the final proof evaluation will be made at HQ or at the regional office. In making such a determination it will consider the complexity of the problem, whether it is specific to the station, etc.

2.3.2.2 The stages involved in the analysis are:

  • HQ sends two copies of the final proof of performance to the regional office within three days of receipt and indicates where the evaluation will be carried out;
  • when the responsible evaluation centre is HQ, the regional office forwards its evaluation comments to HQ within 15 days of receipt of the proof. These comments will be included in the assessment made by HQ;
  • the assessment is made using BPR, Part II, Sections 2.5 and 2.7 ensuring that the parameters are comparable to those of the submitted technical brief;
  • the responsible evaluation centre sends its evaluation comments to the broadcaster within 30 days of the assessment, ensuring that all interested parties, including the broadcasting engineering consultant, are copied.

2.4 Evaluation of the Supplementary Proofs of Performance

The regional offices assess the supplementary proofs.

2.4.1 Evaluation

2.4.1.1 List of items to review

This list is given in Annex 1.

2.4.1.2 General requirements

These are set out in BPR, Part II, Section 2.9.

The measured radiation pattern should correspond to the one approved in the previous supplementary and final proofs of performance, and in the technical brief.

2.4.1.3 Shape of directional pattern

The subject matter is covered in BPR, Part II, Section 2.9.2. The aim is to verify the degree of conformity of the shape of the pattern with previous measurements and authorized patterns.

The ratio measurement approach is suggested if a reliable non-directional pattern is available from the site. Short radials may be required where a reliable non-directional pattern is not available. The following is the ratio method procedure:

  • measure and calculate the ratio of the directional (D) and non-directional (ND) E-fields as per BPR, Part II, Section 2.9.2, giving the following results for each azimuth:

    D/ND ratio = ED/END

    where ED = directional E-field at authorized power (PD)

    END = non-directional E-field at known power (PND)

  • determine the effective (unattenuated) non-directional field at 1 km (END@1km) at the known power using radial measurements;
  • if the directional and non-directional powers are not equal during the field ratio measurements, then the effective non-directional field must be corrected by using the following formula:

F = E sub ND@1km times the square root of (P sub D divided by D sub ND) mV/m

where:

F = corrected non-directional E-field; referred to as the "multiplication factor", since it is used to multiply all ratio points;

END@1 km = effective non-directional E-field at 1 km at power PND;

PD = authorized power used during the directional E-field ratio point measurements.

PND = known power used during the non-directional E-field ratio point measurements.

  • ratio point measurements are chosen at approximately 15 degree intervals around the reference tower, close enough that conductivity effects are minimal, but far enough to avoid nearfield effects, and ratio measurements are made for the directional (D) and non-directional (ND) patterns.
  • the D/ND ratios multiplied by the "F" factor establish the antenna radiation pattern at full authorized power. The information is then plotted on a polar graph and compared with the antenna radiation pattern authorized for the undertaking.

2.4.1.4 Size of the pattern

The aim is to verify the degree of conformity of the size of the pattern with that which was reflected in the previous supplementary proof or final proof. The subject matter is covered in BPR, Part II, Section 2.9.2. E-field measurements are to be taken along a radial of a major lobe of the station pattern. These serve to confirm the effective field at one kilometre, as established in the final proof or previous supplementary proof.

2.4.1.5 Pattern tolerance

The upper limit of the tolerance is either the "expanded" or "modified" pattern, as defined in the International AgreementsFootnote *. Some measured radiations may be higher than permitted on certain azimuths, because of the point of measurement, but it's the broadcaster's responsibility to maintain the size and overall shape of the pattern within the allowed limits. If the upper limit is exceeded on an arc containing more than one point of measurement and if the protection criteria are not met, the proof must be rejected. If however, in the above case, the protection criteria are met, the region should recommend to the broadcaster that he submit a request for augmentations in the radiation pattern.

The normal lower limit is 5% below the theoretical pattern (ref. BPR, Part II, Section 2.9.4) but this should be related to how the service is adversely affected. If this is the case, it is advisable to contact the consulting engineer and touch upon the issue in the response letter to the broadcaster.

2.4.1.6 Augmentations to the pattern

When augmentations to the pattern are required - as determined in 2.4.1.5 above - the regional office requires that the broadcaster submit to HQ an application for the augmentations. Radiation, azimuth and span of each augmentation must be given along with the necessary technical justifications.

HQ will analyze the application, proceed with the international coordination process and upon successful coordination, will prepare a draft reply for inclusion in the regional letter of approval of the supplementary proof of performance.

2.4.1.7 Very old stations

For very old stations without a brief or a final proof of performance, the regional office must liaise with HQ to determine the 0.5 mV/m and Eu contours using the MRG and SKYFALL programs.

2.4.1.8 Accuracy requirements with regard to the location of the measurement points along a radial.

The 1984 CANADA/USA Agreement, Agreement between the Government of Canada and the Government of the United States of America relating to the AM Broadcasting Service in the Medium Frequency Band, can serve as a guide as to the accuracy of the location of the measurement points along a radial (ref: Section 3 of Appendix 6 to Annex 2 of the Agreement). All measurement points should be on-radial to the extent possible. Measurement data along a radial will be considered to be representative of conductivity through an arc of ±10 degrees from the azimuth of the radial. Any off-radial measurement should be accompanied by a showing that they are valid for the intended purpose. Judgment must be used in applying the above criteria since these strict requirements are used only for special cases of international notifications. They should be used only as a reference when discussing with the consultant.

2.4.2 Deadlines

The supplementary proof should normally be evaluated and the letter of reply sent to the broadcaster within 30 days of its receipt. If a proof is unacceptable or if augmentations are required, the regional offices must inform HQ for decisions on appropriate action.

2.4.3 Liaison with HQ

2.4.3.1 An initial copy of the proof of performance is sent to HQ as soon as it is received, and a second copy, bearing the stamp and signature of approval, is sent after assessment. All correspondence pertaining to this assessment must also be sent to HQ.


Annex 1 Items to cover in the review of AM supplementary proofs

Purpose of work

  • Work done, adjustments made, components replaced;
  • Measurements made;
  • General condition of the facilities.

Measurements

  • Listing/description of the equipment used, its accuracy, date of calibration and by whom;
  • Name, signature and stamp of responsible engineer for the measurements;
  • Measurements on the shape of the pattern;
  • Measurements on the size of the pattern;
  • Impedance measurements of each radiating tower and of the operating impedance of the antenna system - BPR, Part II, Section 2.9.2;
  • Log of the station (transmitter) operating parameters - plate voltage and current during the measurement period and calculation of transmitter power output.

Documents required:

  • Approval of proof by a professional engineer - signature and stamp;
  • Polar plot of the measured patterns - BPR, Part II, Section 2.9.3;
  • Plot of the E-field measurements made along a radial and value of the E-field at 1 km - BPR, Part II, Section 2.9.2;
  • Results of antenna impedance measurements - BPR, Part II, Section 2.9.3;
  • Table of current and phase readings of the transmitter and antenna system, as finally adjusted, and of the transmitter output efficiency;
  • Documentation on other work done if it was needed - BPR, Part II, Section 2.9.3.
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