S.I. No. 223/1963:

WIRELESS TELEGRAPHY (CONTROL OF INTERFERENCE FROM IGNITION APPARATUS) REGULATIONS, 1963.

WIRELESS TELEGRAPHY (CONTROL OF INTERFERENCE FROM IGNITION APPARATUS) REGULATIONS, 1963.

I, MICHAEL HILLIARD, Minister for Posts and Telegraphs, in exercise of the powers conferred on me by section 12A (inserted by the Broadcasting Authority Act, 1960 (No. 10 of 1960)) of the Wireless Telegraphy Act, 1926 (No. 45 of 1926), hereby make the following Regulations:--

1. (1) These Regulations may be cited as the Wireless Telegraphy (Control of Interference from Ignition Apparatus) Regulations, 1963.

(2) These Regulations shall come into force on the 1st day of February, 1964.

2. The Interpretation Act, 1937 (No. 38 of 1937), applies to these Regulations.

3. In these Regulations--

"ignition apparatus" means equipment assembled for the purpose of providing and conveying electrical energy for igniting gas or vapour in an internal combustion engine;

"suppressor" means a piece of equipment designed to reduce the field strength of the electro-magnetic energy radiated from the apparatus to which that piece of equipment is fitted when the apparatus is being used;

expressions used in the Schedule hereto have the meanings respectively assigned to them in Part I of that Schedule.

4. These Regulations shall apply to--

(a) any ignition apparatus forming part of an internal combustion engine other than an internal combustion engine which forms part of an aircraft or foreign vessel, if it is to be used;

(b) any ignition apparatus forming part of an internal combustion engine other than an internal combustion engine which forms part of an aircraft, if it is to be sold otherwise than for export or offered or advertised for sale otherwise than for export, or let on hire or offered or advertised for letting on hire, by any person who in the course of business manufactures, assembles or imports such apparatus;

(c) any apparatus which includes one or more components designed to form part of an ignition apparatus and which is assembled for the purpose of testing or demonstrating the operation of one or more of those components, and which when used involves sudden changes of current in a high voltage circuit, if it is to be used.

5. An ignition apparatus or other apparatus to which these Regulations apply shall be so designed, constructed, assembled and installed, and such precautions shall be taken in relation to it (by means of the fitting of a suppressor or otherwise), as to ensure that when used the field strength of the electro-magnetic energy radiated in any direction from the apparatus, as measured and computed in accordance with Regulation 6 of these Regulations, shall not exceed--

(a) fifty microvolts per metre when the measurement is made at a frequency of forty megacycles per second or at any frequency exceeding forty megacycles per second and not exceeding seventy-five megacycles per second;

(b) a voltage increasing linearly with frequency from fifty microvolts per metre at seventy-five megacycles per second, to one hundred and twenty microvolts per metre at two hundred and fifty megacycles per second when the measurement is made at any frequency exceeding seventy-five megacycles per second and not exceeding two hundred and twenty-three megacycles per second.

6. (1) For the purpose of measuring the field strength of electro-magnetic energy referred to in Regulation 5 of these Regulations, the ignition apparatus or the other apparatus to which these Regulations apply shall be tested by means of measuring apparatus of the description and having the physical and electrical characteristics and performance set out in Part II of the Schedule hereto.

(2) The test for field strength shall be made by the method and under the conditions set out in Part III of the Schedule hereto.

(3) The field strength shall be computed as provided in Part III of the Schedule hereto from the readings afforded by the measuring apparatus while the apparatus to which these Regulations apply is being operated.

SCHEDULE.

PART I.

DEFINITION OF EXPRESSIONS USED IN THE SCHEDULE.

Voltage and e.m.f.

References to the voltage or e.m.f. of a sinewave are references to its effective or root mean square value.

Decibel means a unit of transmission giving the ratio of two powers. If P₁ and P₂ represent two values of power and n the number of decibels representing their ratio then n=10 log₁₀ P_l/P₂. If the two powers are dissipated in equal resistive impedances their ratio in decibels may be expressed by n=20 log₁₀ V₁/V₂ where V₁ and V₂ are the voltages across the two resistive impedances.

Applied voltage means the voltage applied to the input terminals of the measuring apparatus.

Reference deflection means the deflection of the needle of the indicating meter of the valve-voltmeter to a mark at the middle of the scale of the meter.

Tuned frequency means the mid-frequency of the band of frequencies for which the measuring apparatus is tuned to accept the applied voltage.

Intermediate frequency means the mid-frequency of the band of frequencies for which the intermediate frequency amplifier of the measuring apparatus is tuned to accept the voltage applied to it.

Image frequency means the frequency, not being the tuned frequency, which combines with the fundamental frequency of the local oscillator to produce the intermediate frequency.

Field strength calibration constant means the number of decibels that must be added to the reading of the measuring apparatus, when a measurement of field strength is made as prescribed, to give the value of field strength in decibels above one microvolt per metre.

PART II.

DESCRIPTION AND SPECIFICATION OF CHARACTERISTICS AND PERFORMANCE OF MEASURING APPARATUS FOR USE IN THE FREQUENCY RANGE 40 Mc/s TO 223 Mc/s.

1. General description

The measuring apparatus shall be a calibrated radio receiver, designed for the measurement of the field strength of radio frequency noise. For this measurement the input terminals of the receiver shall be connected to a dipole aerial by a balanced screened feeder. The receiver shall be of the superheterodyne type and comprise a radio-frequency (R.F.) amplifier, a frequency changer, an intermediate-frequency (I.F.) amplifier and an output valve-voltmeter. Attenuators, calibrated in decibels (db), shall be provided in the input circuits of both R.F. and I.F. amplifiers. The indicating meter of the valve-voltmeter shall have a scale provided with zero and full-scale marks and a reference deflection mark at mid-scale. The measuring apparatus shall be calibrated in terms of a known intensity of a continuous wave field in which the associated aerial system is placed. Facilities shall be provided so that, whenever a measurement is to be made, the gain of the receiver of the measuring apparatus may be set to the gain used when it was calibrated.

2. Performance characteristics

(1) Accuracy of setting frequency. The measuring apparatus shall be capable of being set, to an accuracy of ±1 per cent., to receive any frequency within its range.

(2) Sensitivity and accuracy of measuring apparatus--field strength measurement. Values of field strength greater than 20 microvolts per metre, at any frequency within the range of the measuring apparatus, shall be measurable to an accuracy of ±3 db.

(3) Attenuators. The calibrated attenuators shall be so constructed and disposed that no performance characteristic of the set, apart from gain, is significantly affected by variations in their settings.

(4) Overload characteristic. With the measuring apparatus adjusted to give reference deflection of the meter for an applied sinewave voltage of any value between 20 microvolts and 100 millivolts, the sinewave voltage measured at the input of the valve-voltmeter shall be proportional to the applied voltage within ±1 db up to a voltage 40 db above that producing reference deflection.

(5) Overall frequency characteristic. The variation with frequency of an applied sinewave voltage to produce a constant voltage at the input to the valve-voltmeter, when no alteration is made to the tuning of the measuring apparatus, shall not exceed the limits of the shaded area of Figure 1.

(6) Frequency characteristic of radio-frequency amplifier. The increase of an applied sinewave voltage needed to produce a constant voltage at the control grid of the frequency changer valve shall be not less than 6 db when the frequency of the applied voltage is varied from the tuned frequency by ± 2.5 Mc/s.

FIG. 1.--Overall Frequency Characteristic of Measuring Apparatus--Schedule Part II Paragraph 2 (5).

(7) Spurious responses. The applied sinewave voltage of the tuned frequency which produces reference deflection of the meter shall be at least 80 db lower than the applied voltage at any other frequency which combines with a harmonic and not the fundamental frequency of the local oscillator to produce reference deflection.

(8) Image frequency response. The ratio of the applied sinewave voltages which produce reference deflection at the image frequency and at the tuned frequency respectively shall be at least 40 db.

(9) Intermediate frequency response. The ratio of the applied sinewave voltages which produce reference deflection at the intermediate frequency and at the tuned frequency respectively shall be at least 40 db.

(10) Screening. The overall screening shall be such that, with the receiver tuned to any frequency within its range and the gain of the receiver adjusted to that used for that frequency when the measuring apparatus was calibrated, the change in the I.F. attenuator setting required to return the meter to reference deflection when an external electro-magnetic field of that frequency and of a strength of 86 db above 1 microvolt per metre is switched on shall not exceed 1 db. This requirement shall be met for all orientations of the measuring apparatus. For this test screening covers may be placed over the input terminals.

3. Input circuit

The impedance at the input terminals of the measuring apparatus shall be balanced and shall have a value of 75 ± 15 ohms and a phase angle within the limits ± 20 degrees at any frequency within the range of the measuring apparatus.

4. Aerial and feeder

(1) Aerial. The aerial shall consist of a dipole of a length not greater than 3 metres nor less than 0.75 metres, which shall be supported so that its centre is not less than 2 metres above the base of the support when a measurement of field strength is made.

(2) Feeder. The aerial shall be connected to the aerial input terminals of the measuring apparatus by a twin balanced and screened feeder of a nominal characteristic impedance of 75 ohms. The feeder shall be led at right angles from the dipole for a distance of at least 1 metre.

(3) Balance/Unbalance ratio. The balance/unbalance ratio at the aerial end of the feeder shall be not less than 20 db when measured as follows:--

A generator of internal impedance R where R is not greater than 5 ohms, shall be connected to the feeder and measuring apparatus as shown in Figure 2 (a) and as shown in Figure 2 (b) in turn. The ratio of the generator e.m.f.'s which produce reference

deflection of the meter in the unbalanced connection, (e¹ Figure 2 (a) ) and the balanced connection (e² Figure 2 (b) ) respectively, shall be taken as the balance/unbalance ratio.

5. Output circuit (valve-voltmeter)

(1) Linearity. The performance of the rectifier and of any associated circuits of the valve-voltmeter shall be such that the current through the indicating meter is linearly related to the sinewave voltage input to the rectifier, to within ±10 per cent. of that voltage, for all values of input voltage from 0.5 to 2.5 times the value producing reference deflection.

FIG. 2.--Schedule Part II Paragraph 4 (3).

The application to the input of the rectifier of the sinewave voltage which produces reference deflection shall cause an increase of 1.75 volts ± 10 per cent., in the steady voltage across the rectifier load.

The increase in the sinewave voltage at the input of the rectifier required to increase the meter reading from reference deflection to full-scale deflection shall be not less than 5.5 db nor more than 6.5 db.

(2) Charge time-constant. A sinusoidal voltage of frequency equal to the intermediate frequency, which when continuously applied to the input terminals of the intermediate frequency amplifier produces reference deflection, shall, when suddenly applied at the same point, cause the change of voltage across the output circuit of the rectifier to reach 0.63 times the final value of the change of voltage in not less than 0.8 milliseconds and not more than 1.2 milliseconds.

In this test, the input terminals of the I.F. amplifier shall be disconnected from the preceding circuits of the measuring apparatus.

(3) Discharge time-constant. The time taken for the current in the meter circuit to decrease by 0.63 times its initial value after an applied voltage as specified in paragraph 5 (2) above is suddenly removed shall be not less than 450 milliseconds and not more than 550 milliseconds.

(4) Indicating meter. The indicating meter shall be of the permanent magnet moving-coil type in which the deflection of the needle is directly proportional to the current passing through the meter. Under the conditions of use of the measuring apparatus the damping of the meter shall be such that, when a current of a value which produces a final steady full-scale deflection is suddenly applied to the meter, the time of rise to 80 per cent. of full-scale deflection is not less than 240 milliseconds and not more than 360 milliseconds and the overswing is less than 5 per cent. of the full-scale deflection.

6. General requirements

(1) Gain setting. The accuracy of adjustment of the measuring apparatus shall be such that two successive measurements of any given input voltage (having a value within the range of measurement of the apparatus), between which any adjustment of the operating controls may be made, shall not differ by more than 1 db.

(2) Monitoring. Provision shall be made for aural presentation of the receiver output for monitoring purposes.

PART III.

METHOD AND CONDITIONS OF MEASURING FIELD STRENGTH.

1. Method of measurement

(1) With the aerial and feeder disconnected from the receiver of the measuring apparatus and the I.F. attenuator set at maximum loss, the zero control of the valve-voltmeter shall be adjusted to bring the needle of the indicating meter to the zero mark.

(2) The receiver shall be tuned to the frequency, as indicated by the main tuning dial calibrations, at which it is desired to make the measurement, and its gain shall be set to that used when the measuring apparatus was calibrated.

(3) The feeder and a dipole aerial of length approximating as closely as practicable to that used for the calibration of the measuring apparatus shall be connected to the receiver. The aerial may be oriented in any position for the purpose of the measurement. The R.F. amplifier tuning of the receiver shall be adjusted to give maximum deflection of the meter needle.

(4) The attenuators shall then be adjusted to bring the meter needle to the reference deflection mark; the R.F. attenuator being adjusted so that the I.F. attenuator is set to the lowest possible value in excess of 10 db.

(5) The field strength in decibels above 1 microvolt per metre will be given by the sum of the readings of the two attenuators plus the field strength calibration constant appropriate to the frequency at which the measurement is being made. If this value is X decibels, the field strength in microvolts per metre is given by the antilog to the base 10 of .

2. Conditions of testing

(1) When an ignition apparatus to which these Regulations apply is being tested it shall be tested as installed in the internal combustion engine, and in a case in which the internal combustion engine forms part of a vehicle or vessel, the test shall be made with the engine installed in the vehicle or vessel.

(2) When an apparatus referred to in paragraph (c) of Regulation 4 of these Regulations is being tested it shall be tested under its normal conditions of installation and use.

(3) All electrical apparatus, other than the apparatus under test, which forms part of the vehicle, vessel or engine (if any) and which in operation could appreciably affect the result of the test, shall be switched off or otherwise prevented from being energised by complete or partial electrical disconnection.

(4) The distance between the aerial of the measuring apparatus and the nearest point on the apparatus under test shall be not less than 33 feet.

(5) To ensure that no extraneous noise or signal of sufficient magnitude materially to affect the measurement is present, a measurement of field strength shall be taken, both before and after the main test, without the apparatus under test being energised. If the maximum reading obtained on the main test exceeds the maximum reading obtained on either of these check tests by at least 10 decibels, the maximum reading obtained on the main test is to be regarded as not materially affected by extraneous noise or signals. Otherwise, the readings obtained on the main test are to be regarded as materially affected by extraneous noise or signals, and the result of the main test shall be disregarded for the purpose of these Regulations.

GIVEN under my Official Seal, this 8th day of November, 1963.

MICHAEL HILLIARD.

EXPLANATORY NOTE.

These Regulations prescribe the requirements to be complied with by manufacturers, assemblers, importers, and users of ignition apparatus which forms part of an internal combustion engine. They apply to such apparatus in vehicles, vessels or engines but aircraft and foreign vessels are excluded from the scope of the Regulations as is also equipment intended for export. The Regulations also apply to apparatus which is assembled for the purpose of testing or demonstrating the components of ignition equipment and which when used causes undue interference with radio and television reception.

The requirements to be observed are prescribed in terms of the maximum permitted field strength of the electro-magnetic energy radiated from the apparatus when it is being used. The Schedule sets out the method of measurement, the conditions under which measurements are to be made and the description and specification of the measuring apparatus.