NEW ZEALAND GAZETTE

No. 209

(3) The level of the open-circuit voltage of the signal generator shall be regarded as the signal applied to the receiver under test.

7. Selectivity—

(1) The selectivity preceding the final detector shall be variable either continuously or in steps, and shall satisfy the following requirements throughout the frequency ranges specified. For this test the automatic gain control (a.g.c.) shall be rendered inoperative:

Not less than 6 dB discrimination to be obtained at frequencies removed from tune by:

| | 4 kHz | 1.5 kHz | 0.5 kHz (does not apply below 100 kHz) |

At least 30 dB discrimination to be obtained at frequencies removed from tune by:

| | 6 kHz | 2-5 kHz | 1 kHz | 0.25 kHz |

At least 40 dB discrimination to be obtained at frequencies removed from tune by:

| | 10 kHz | 5 kHz | 2.5 kHz | 0.75 kHz |

At least 60 dB discrimination to be obtained at frequencies (other than the image frequency) removed from tune by:

| | 20 kHz | 10 kHz | 5 kHz | 5 kHz |

At least 80 dB discrimination to be obtained at frequencies other than the i.f. and image frequencies removed from tune by:

| | 45 kHz | 35 kHz | 25 kHz | 25 kHz |

For the purpose of this test no discrimination exceeding 80 dB against any interfering signal of frequency greater than 1.6 MHz.

(2) The image rejection ratio and the intermediate-frequency rejection ratio of a superheterodyne receiver shall not be less than the values given in the following tables. For these tests the a.g.c. shall be rendered inoperative:

8. Sensitivity—

The standard output levels specified in subclauses (1) and (2) of clause 5 of this Part of this Schedule shall be obtainable at all bandwidth settings, with the a.g.c. both on and off and with the under-mentioned levels:

9. Signal/Noise Ratio—

(1) With any input signal, either of Class A1 or A2, of the level specified in clause 8 of this Part of this Schedule and with the receiver gain adjusted to give standard output, the signal/noise ratio shall not be less than the under-mentioned values. For this test the requirements shall be met whether a.g.c. is operative or not:

(2) No relaxation of these limits shall be allowed for spurious whistles.

10. Automatic Gain Control—

(1) The receiver shall be fitted with an a.g.c. capable of efficient operation on signals of Classes A1, A2, and A3 at all frequencies in the range between 1500 kHz and 28 MHz.

(2) With an input signal of Class A2 at the appropriate level specified in clause 8 of this Part of this Schedule and of any frequency within the ranges between 1500 kHz and 28 MHz, then:

(a) When the receiver is adjusted to give standard output, an increase in input of 20 dB shall result in an improvement in the signal/noise ratio to at least 15 dB above the appropriate minimum signal/noise ratio specified in clause 9 of this Part of this Schedule:

(b) With the receiver adjusted to give an output 10 dB below standard output, an increase in input of 60 dB shall not increase the output by more than 10 dB. Under this condition the total harmonic content of the output voltage shall not exceed 5 percent.

(3) The charge time-constant of the a.g.c. system shall be between 0.05 and 0.2 second, and the discharge time-constant shall be between 0.5 and 2 seconds.

(4) Means shall be provided for switching off the a.g.c.

11. Limiting—

With the a.g.c. switched off and with the receiver adjusted to give standard output with a Class A1 input signal 20 dB above the appropriate level specified in clause 8 of this Part of this Schedule, then an increase in the input of 60 dB shall not increase the output by more than 10 dB.

12. Blocking—

(1) With the bandwidth set to “intermediate,” and the a.g.c. switched on wherever available, the receiver shall be adjusted to give standard output with an input wanted signal of Class A2 at a level of 60 dB above 1µV and of any frequency in the range 160 kHz to 28 MHz.

The simultaneous application of a Class A1 input signal at a level of 100 dB above 1µV and at a frequency 10 kHz above or below that of the wanted signal shall not cause a change in output exceeding 3 dB.

(2) The receiver shall be adjusted, with the bandwidth at “narrow” and the a.g.c. switched off, and the audio-frequency volume control set at maximum to give standard output with an input wanted signal of Class A1 at a level of 30 dB above 1µV and of any frequency between 15 and 160 kHz.

The simultaneous application of a Class A1 input signal at a level of 70 dB above 1µV and at a frequency 5 kHz above or below the wanted signal shall not cause a change in output exceeding 3 dB.

13. Cross Modulation—

The receiver shall be adjusted and an input wanted signal applied as described in clause 12 (1) of this Part of this Schedule and the modulation only of the signal then switched off.

The simultaneous application of a Class A2 input signal at a level of 90 dB above 1µV and at a frequency 10 kHz above or below that of the wanted signal shall not cause an output equivalent to a signal/noise ratio exceeding 10 dB.