BC-11 — FM/NAV/COM Service Compatibility Analysis

Issue 1
May 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


FM transmitting undertakings are assigned in the frequency band 88-108 MHz. Aeronautical radionavigation services (NAV) are assigned in the band 108-116 MHz and aeronautical radiocommunication services (COM) in the band 116-137 MHz. As a result, FM broadcasting assignments may present a potential for interference to these aeronautical services.


The purpose of this procedure is to assess the potential for interference from a proposed FM undertaking to these aeronautical services, resolve any problems and ensure compatibility between all the services concerned after the broadcasting undertaking is assigned.


A compatibility analysis shall normally be performed by Headquarters, for every application for an FM broadcasting undertaking. As a result of this analysis, the application may be considered acceptable, conditionally acceptable or returned to the applicant for revisions.

1. Interference Prediction Model

1.1 A potential for interference to aeronautical NAV and COM services exists when the following types of interference mechanisms enter into play:

A. Type A interference - normally radiated by FM undertakings.

  1. Type A1 - spurious emissions generated by a single transmitter or intermodulation products generated by multiplexed transmitters, falling in the aeronautical frequency bands.
  2. Type A2 - useful FM sideband energy falling in the aeronautical frequency bands (only from FM transmitters operating near 108 MHz - COM services are not affected).

B. Type B interference - normally generated in the aeronautical receiver.

  1. Type B1 - intermodulation generated as a result of two or more FM signals whose product falls on a desired RF channel in use by the aeronautical receiver. It should be noted that at least one of the FM signals must be strong enough to drive the receiver into non-linearity.
  2. Type B2 - overload of the RF section of an aeronautical receiver due to one or more FM signals, leading to desensitization.

1.2 An interference prediction model has been developed jointly by Industry Canada and Transport Canada (TC), based on protection criteria and assessment methods recommended by the former International Radio Consultative Committee (CCIR). Refinements related to specific aeronautical assignment parameters have been added to help resolve problems on a case-by-case basis.

2. Interference Analysis

2.1 Each application for an FM transmitting undertaking (primary or secondary assignment) is subject to an FM/NAV/COM compatibility analysis. Depending on the result, the following may take place:

  1. if no interference is predicted, it is presumed that compatibility exists;
  2. if the potential for interference is low, a conditional technical acceptance is granted subject to:
    • monitoring (Department or TC) during on-air testing of the undertaking;
  3. if the potential for interference is high, the engineering brief is considered not acceptable and the application is returned.

2.2 In complex electromagnetic environments, flight tests may be required to resolve a problem of incompatibility. This is a rare occurrence and the applicant will undertake this procedure at his own cost.

2.3 A check list, incorporating the required monitoring tests, is received from TC and approved by the Department (a copy is sent to the regional or district office). The Department's "Evaluation Comments on Broadcast Application" which are sent to the Canadian Radio-television and Telecommunications Commission (CRTC), will reflect the application status from an FM/NAV/COM point of view.

3. Industry Canada/Transport Canada Conflict

In case of dissension between the Department and TC on the interpretation of the results of the analysis, the existing administrative agreement calls for a committee to be set up and chaired by the dissenting party. This committee will report on the problem with recommendations to senior management. The same procedure takes place if significant problems materialize during the period of on-air testing of an FM undertaking.

4. Conditional Technical Acceptability

When conditional technical acceptability is given, the applicant is notified accordingly. If the application is approved by the CRTC (also conditionally), the letter of authority issued by the Department will identify the requirement for tests. It will also specify the period required as notice to the Department before the on-air testing takes place. Adherence to the terms of the notice is mandatory. Monitoring may be undertaken by the Department or Transport Canada or both.

5. On-Air Tests

5.1 Testing is conducted under the supervision of the Department or TC or both and broadcasters shall cooperate fully.

5.2 The FM undertaking shall be tested for the authorized parameters and pass the monitoring and/or flight tests before it is authorized to start normal scheduled broadcasting. However, if interference is detected, remedial measures shall be taken to eliminate the interference. If interference is not eliminated, authority for scheduled on-air broadcasting will be denied.

5.3 For further information and guidance on this phase, consult Broadcasting Circular 15 (BC-15), On-Air Testing Procedures for AM, FM and TV Broadcasting Undertakings.

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