ETSI ETS 300 441, Инструкция по эксплуатации

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Page 21
ETS 300 441: February 1996
NOTE: The receiver should be designed to prevent excessive noise at the receiver output in
the absence of input signals.
7.11.1 Methods of measurement
a) to test the AGC at low input signal levels, an A2A test signal at the carrier frequency 2 182 kHz
modulated to a depth of 30 % at 1 kHz, shall be applied to the receiver input. The input level shall
be adjusted to give a SND/N ratio of 10 dB. The volume control shall be adjusted to give standard
output power. The input level shall then be increased by 20 dB and the SND/N ratio shall be
measured;
b) to test the AGC at high input signal levels, an A2A test signal at the carrier frequency 2 182 kHz
modulated to a depth of 30 % at 1 kHz, shall be applied to the receiver input. The input level shall
be adjusted to give a SND/N ratio of 10 dB. The volume control shall be adjusted to give an output
level 10 dB below the standard output power. The input level shall then be increased by 70 dB and
the change in output power shall be measured.
7.11.2 Limits
a) under the test conditions specified in subclause 7.11.1 a), the SND/N ratio shall increase to at least
25 dB;
b) under the test conditions specified in subclause 7.11.1 b), the output power shall not increase by
more than 10 dB.
7.12 Audio frequency gain controls
7.12.1 Definition
The audio frequency gain control is a manual volume control by which the audio output can be varied
between the maximum level and a low but audible level.
7.12.2 Method of measurement
It shall be possible with a pre-set control not readily accessible to the operator, to adjust the low output
level. Any combined setting of the manual and pre-set volume controls shall not give an output power of
less than 1 mW at the usable sensitivity level as measured in accordance with subclause 7.2.
7.12.3 Limit
With the manual volume control at minimum position the pre-set control shall allow for a range of output
power of at least 12 dB.
7.13 Protection of input circuits
7.13.1 Definition
The protection of the input circuit is the ability of the antenna input to stand large voltages for a specified
time.
Provisions shall be made for protecting the receiver and muting its output when the ship's own
radiotelephone transmitter is radiating on 2 182 kHz.
7.13.2 Method of measurement
The receiver shall not suffer damage when an unmodulated radio frequency test signal of 30 V rms is
applied to its input as specified in subclause 5.7 for a period of 15 minutes at any frequency in the range
100 kHz to 28 MHz.
7.13.3 Limit
The receiver shall operate normally without further attention when the test signal is removed.