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BETS-5 — Technical Standards and Requirements for AM Broadcasting Transmitters

Technical Standards and Requirements for AM Broadcasting Transmitters
(PDF, 76 KB, 21 pages)

Issue 1
November 1, 1996

Spectrum Management
Broadcasting Equipment Technical Standard

Purpose

This document contains the technical standards and requirements for the issuance of a Technical Acceptance Certificate (TAC) for AM broadcasting transmitters.

A certificate issued for equipment classified as type approved or as technically acceptable before the coming into force of these technical standards and requirements is considered to be a valid and subsisting TAC.

A Technical Acceptance Certificate is not required for equipment manufactured or imported solely for re-export, prototyping, demonstration, exhibition or testing purposes.

Table of Contents

  1. General
  2. Testing and Labelling
  3. Standard Test Conditions
  4. Transmitting Equipment Standards
  5. Equipment Requirements
  6. RF Carrier Performance Standards

1. General

1.1 The standards and requirements in this document are the pre-requisite conditions for the issuance of a Technical Acceptance Certificate (TAC) for AM broadcasting transmitters.

1.2 Those seeking to obtain a Technical Acceptance Certificate for AM broadcasting transmitters shall, at their own expense, carry out the required tests and send to the Department a certification submission and an engineering brief prepared in accordance with Broadcasting Equipment Standards Procedure 100 (BESP-100).

1.3 The engineering brief, signed by a professional engineer licensed by a provincial association, shall demonstrate that the equipment meets the technical standards in this document.

1.4 Notwithstanding the fact that a radio apparatus meets all applicable requirements, the Department reserves the right to require that adjustments be made to the equipment should it cause interference.

1.5 Any major design or component changes, other than the replacement of defective components by equivalent parts, will void the approval unless notified to and approved by the Department.

1.6 This document replaces RSS-150, Issue 2.

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2. Testing and Labelling

2.1 Sections 3 to 6 contain the general equipment standards and the emission standards which relate to the radiated signal of the AM transmitting equipment. Compliance to the standards of these sections shall be supported by an engineering brief stating measurement results in accordance with Broadcasting Equipment Standards Procedure 100 (BESP-100).

2.2 Annex A contains the performance standards recognized by the industry to ensure quality operation of AM broadcasting equipment. Compliance with the standards of Annex A shall be supported by a statement certifying that the equipment meets the standards. The submission of test results for these performance measurements is not required but the results shall be kept on file by the applicant.

2.3 This document covers the transmitting equipment proper: namely from audio input terminals to the output terminals including any separate RF amplifiers and filters.

2.4 In the event that the equipment fails to function during the certification tests, all tests affected by the failure shall be repeated after the fault has been corrected.

2.5 The transmitting equipment shall be capable of meeting the standards in this document on any AM channel and at the rated power output for which it is designed to operate.

2.6 Each certified broadcasting equipment must display in a conspicuous location:

  1. the manufacturer's name, trade or brand name (if different from the manufacturer's name);
  2. the model identification;
  3. the serial number;
  4. the Technical Acceptance Certificate number;
  5. the name of the certification assignee.

2.7 The identification label must be indelible, tamper-resistant and affixed permanently or stamped in such a manner as not to be removable except by destruction or defacing.

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3. Standard Test Conditions

3.1 Definition

Standard test conditions are those conditions which shall apply to a transmitting equipment while it is being tested for minimum requirements. These conditions apply unless otherwise specified. Where no special conditions are called for in the tests, the conditions shall be those specified by the manufacturer for normal operation, and these shall be stated in the test report.

3.2 Standard Test Voltage

Standard test voltage shall be one of the rated power supply voltages specified by the manufacturer.

3.3 Standard Temperature

Standard temperature shall be 20° C ± 5° C. The temperature shall be recorded in the test report.

3.4 Standard Test Load

Standard test load shall have a resistive impedance characteristic and be capable of dissipating the output power of the transmitting equipment. At the test frequency, the resistive component of the test load shall be within 5% of the load impedance into which the transmitting equipment was designed to operate. The reactive component of the test load shall not be greater than 5% of the resistive component over the range of ±10 kHz from the test frequency.

3.5 Standard Test Frequencies

Standard test frequencies shall be the carrier frequency of the channel for which the transmitting equipment is designed to operate. For transmitting equipment capable of operating on any one channel in 535 - 1,705 kHz band, tests shall be made on two channels, one near each end of the band. The test frequencies shall be specified in the test report.

3.6 Standard Test Input Signal

The standard audio test signal shall be a 400 Hz sine wave.

3.7 Standard Test Equipment

All measurements shall be made with instruments having sufficient accuracy to ensure that no appreciable error occurs due to test equipment in the measurements of the transmitter under test.

3.8 Standard Test Set-up

Unless otherwise specified, all tests shall be made with the carrier at rated power output and modulated with the standard test input signal.

3.9 Warm-up Time

The transmitting equipment and test equipment shall be switched on at least 30 minutes before any test is started, unless otherwise stated.

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4. Transmitting Equipment Standards

4.1 Transmission System

An AM broadcasting transmitting equipment consists of all the apparatus necessary to convert the audio input signal to an amplitude modulated RF carrier at a channel frequency in the 535 to 1,705 kHz frequency band.

4.2 Type of Emission

The designation of modulation and emission refers to the manner in which the carrier is modulated and transmitted. The transmitting equipment shall produce A3EGN emission.

4.3 Carrier Frequency Adjustment

The transmitting equipment shall be capable of operation in accordance with these standards on any channel in the specified carrier frequency range without change in construction other than changing frequency determining components. Provision shall be made for trimming the carrier frequency to the assigned frequency under normal operating conditions.

4.4 Power Supply Rating

The AC voltage input shall be single phase or three phase, at a frequency of 60 Hz. Voltage, frequency and maximum kVA requirements shall be indicated on the transmitting equipment.

4.5 Phase-to-Phase Loading

The transmitting equipment, if rated above 10 kVA input, shall present a balanced load to the AC mains such that the current in each phase shall be within 10% of the average of the three currents.

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5. Equipment Requirements

5.1 Design

Transmitting equipment shall be designed according to good current engineering practice.

5.2 Nameplate

Labelling shall be according to the requirements in 2.6.

5.3 Protection of Personnel

The transmitting equipment shall be so constructed that all hazardous components are totally enclosed, or protected from accidental contact by personnel. The transmitting equipment enclosure shall be sufficient to provide adequate personnel safety during operation.

5.4 Equipment Changes and Modifications

Any major design or equipment changes outside the replacement of defective components by equivalent parts made to an approved equipment will void the approval unless notified to and approved by the Department. The notification must provide information demonstrating that the modification provides equal or improved transmitting equipment performance.

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6. RF Carrier Performance Standards

6.1 Power Output Rating

6.1.1 Definition

The power output rating of a transmitting equipment is the carrier power at which the transmitting equipment may be operated into the test load.

6.1.2 Method of Measurement

The carrier shall be continuously modulated with the standard test input signal at a level producing 50% modulation for a period of 3 hours followed immediately by 95% modulation for a period of 5 minutes. The output shall be connected to the standard test load. The output power of the carrier shall be measured by using a suitable power measuring device. The method shall be described in the test report.

6.1.3 Standard

6.1.3.1 The standard rating of power output for the transmitting equipment shall be as specified by the individual manufacturer. The transmitting equipment shall be capable of delivering the standard output rating plus 10% for transmitting equipment rated below 10 kW or the standard output rating plus 6% for transmitting equipment rated 10 kW or above. The transmitting equipment shall be capable of being adjusted to deliver the rated power output when the AC input voltage is 5% above or below rated value.

6.1.3.2 The test report shall state the power output limits over which the transmitting equipment complies with this document.

6.2 Modulation Capability

6.2.1 Definition

Modulation capability is the extent to which the carrier can be modulated.

6.2.2 Method of Measurement

Using an oscilloscope, spectrum analyser, modulation monitor, or any other suitable method, the modulation capability shall be measured. The method shall be described in the test report.

6.2.3 Standard

6.2.3.1 Standard (Monophonic Operation)

The transmitting equipment shall be capable of modulation to 95% on positive and negative peaks at any carrier frequency within the broadcast band.

6.2.3.2 Standard (Stereophonic Operation)

The transmitting equipment shall be capable of amplitude modulation to 85% on positive and negative peaks and capable of phase modulation to 1.25 radians (71.5%) at any carrier frequency within the broadcast band.

6.3 Carrier Frequency Stability

6.3.1 Definition

The carrier frequency stability is the ability of the transmitter to maintain a mean standard test frequency.

6.3.2 Method of Measurement

6.3.2.1 After a warm-up period of one hour at rated AC input voltage, measure the frequency of the carrier at one minute intervals during a period of fifteen minutes. From those measurements determine the mean test frequency for the carrier. Then at temperatures of 5° C and 45° C measure the operating frequency at supply voltages of 85, 100 and 115%. A period of 30 minutes should be allowed to enable the unit under test to achieve temperature stability before performing the measurements.

6.3.2.2 Where it is not practical to subject the complete transmitting equipment to the specified test conditions, it is permissible to isolate and separately measure the stability of the frequency-determining elements of the transmitting equipment under the specified conditions.

6.3.3 Standard

The frequency stability of the carrier shall remain within 10 Hz of the mean test frequency.

6.4 Carrier Level Shift

6.4.1 Definition

The carrier level shift is the change in average carrier amplitude during modulation expressed as a percentage.

6.4.2 Method of Measurement

Carrier level shift shall be measured by a suitable modulation monitor.

6.4.3 Standard

The carrier level shift for 95% modulation shall not exceed 5%.

6.5 Spurious Emissions

6.5.1 Definition

Spurious emissions are radio frequency signals appearing at the transmitting equipment output terminals on frequencies other than the specified carrier frequency and modulation products.

6.5.2 Method of Measurement

The transmitting equipment shall be operated into the standard test load at rated power. The carrier shall be modulated with the standard test input signal at 95% modulation. Using a sampling device measure all spurious emissions up to the third harmonic of the carrier frequency. The voltage of the emission shall be measured with a frequency selective instrument. The attenuation versus frequency characteristics of the power sampling device and the load used in this test shall be known over the range of frequencies involved. Record all spurious outputs in dB relative to rated power except those more than 20 dB below the values in 6.5.3.

6.5.3 Standard

Spurious emissions of the transmitting equipment shall not exceed the values given in the following table:

Spurious Emission Maximum Value
(a) between 15 kHz and 30 kHz from the carrier frequency -25 dB*
(b) more than 30 kHz and up to and including 75 kHz from the carrier frequency -35 dB*
(c) more than 75 kHz from the carrier frequency -(43 + 10 log P)* or - 80 dB* whichever is the higher signal level
P = power in watts

* Referred to the power level of the unmodulated carrier.

In addition, when the oscillator crystal is removed or deactivated, spurious radiation at any frequency including the assigned carrier frequency shall be no greater than the value specified in (c) above.

6.6 Cabinet Radiation

6.6.1 Definition

Cabinet radiation is any emission from the transmitting equipment housing or enclosure from sources other than a normal output port.

6.6.2 Method of Measurement

The transmitting equipment shall be operated at rated power output. A receiving antenna, located alternately at a known distance between three and ten metres from at least three sides of the transmitting equipment (i.e. front, back, left or right hand side), shall be connected to a calibrated field strength metre or frequency selective voltmeter. Field strength measurements shall be made of all emissions (including the fundamental and harmonics of the carrier frequency) up the third harmonic of the carrier frequency. For the measurement, the receiving antenna shall be rotated in all three planes and the maximum received field shall be noted (allowance shall be made for antenna factor and transmission line loss of the measuring equipment). Using the free space formula below, calculate the reference field strength.

E = 7 √P / r volts per metre

Where P is the rated output power in watts and r is the distance in metres.

6.6.3 Standard

Emissions at any frequency shall be at least 54 dB below the calculated field strength reference level. Any radiation weaker than 70 dB below the reference level need not be recorded.

6.7 Occupied Bandwidth

6.7.1 Definition

The bandwidth occupied by the carrier and associated modulation products such that they fall within the specified limits.

6.7.2 Methods of Measurement

Measurement of the occupied bandwidth shall be conducted using a standard noise test signal. The test signal shall consist of a white noise source with USASI (United States of America Standards Institute) weighting. The weighting is produced by filtering white noise with a 100 Hz, 6 dB per octave high pass network and a 320 Hz, 6 dB per octave low pass network. The USASI noise signal is then passed through a pulser circuit wherein the ratio of the peak to average amplitude of the noise signal is set to 20 dB at the output of the pulser.

The pulser shall operate at a frequency of 2.5 Hz with a duty cycle of 12.5%. The noise test signal from the pulser shall be input to the transmitting equipment through a network providing a modified 75 microsecond preemphasis and a 10 kHz low pass filter. The preemphasis is a modified 75 microsecond curve with a high frequency break point at 8,700 Hz. The low pass filter is a sharp cutoff filter providing attenuation of 15 dB at 10 kHz, 30 dB at 10.5 kHz, 40 dB at 11 kHz and 50 dB at 15 kHz and greater. The noise source is split into two channels left and right that have identical spectral distributions. The individual level of each channel is adjusted to obtain the ratio of L + R (sum information) to L - R (difference information) of 3 dB (i.e. a ratio of 1.4 to 1).

A suitable swept frequency RF spectrum analyser shall be used to measure the spectrum emissions. The spectrum analyser setup shall consist of:

  1. 300 Hz resolution bandwidth;
  2. 5, 10 or 20 kHz/horizontal division (as appropriate);
  3. 10 dB/vertical division;
  4. Reference: Carrier peak;
  5. Peak hold: 10 minutes duration.

Using the appropriate scan width, measure the emission within ±30 kHz of the carrier.

6.7.3 Standard

Emissions from a stereophonic AM transmitting equipment consisting of the carrier and associated modulation products shall be confined to frequencies within ±15 kHz of the carrier. Emissions appearing on any frequency more than 15 kHz and up to 30 kHz shall be attenuated at least 25 dB below the level of the unmodulated carrier.

6.8 Unwanted Emissions

6.8.1 Definition

Unwanted emissions are emissions on a frequency or frequencies outside the occupied bandwidth which result from the modulation process but exclude spurious emissions.

6.8.2 Method of Measurement

Using the same setup as in paragraph 6.7.2 and the appropriate scan width, measure the emissions within ±100 kHz of the carrier.

6.8.3 Standard

Any emissions appearing on a frequency removed by more than 30 kHz from the carrier shall be attenuated at least:

  1. 35 dB below the level of the unmodulated carrier for any frequency more than 30 kHz and up to 75 kHz from the carrier;
  2. 43 + 10 log P (Power in Watts) dB or 80 dB, whichever is the lesser attenuation, below the level of the unmodulated carrier for any frequency more than 75 kHz from the carrier.
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