NAVIGATION (DIRECTION-FINDERS) REGULATIONS
- Reprinted as at 31 July 1982 (HISTREG CHAP 189 #DATE 31:07:1982)
*1* The Navigation (Direction-Finders) Regulations (in force under the Navigation Act 1912) as shown in this reprint comprise Statutory Rules 1968 No. 27 as amended by the other Statutory Rules specified in the following table: ---------------------------------------------------------------------------- Date of Application, saving Year and notification in Date of or transitional number Gazette commencement provisions ---------------------------------------------------------------------------- 1968 No. 27 20 Mar 1968 20 Mar 1968 1969 No. 144 18 Sept 1969 18 Sept 1969 - 1982 No. 14 25 Jan 1982 R. 1: 26 Jan 1982 Remainder: 25 Jan 1982 - ---------------------------------------------------------------------------- NAVIGATION (DIRECTION-FINDERS) REGULATIONS - TABLE OF PROVISIONS
TABLE
TABLE OF PROVISIONS
Regulation
1. Citation
2. Repeal
3. Interpretation
4. Exemptions
5. Ships to be provided with direction-finders
6. Requirements for direction-finders
7. Installation of direction-finders
8. Broadcast receiver aerials
9. Supply of electrical energy
10. Protection of high voltage parts
11. Means of communication
12. Wiring diagram and instructions
13. Maintenance of direction-finders
14. Calibration
15. Verification of calibration tables and curves
16. Records of calibration and verification
17. Master to make calibration records available to radio surveyor
18. Charging of batteries
19. Supply of electrical energy for testing
20. Use of direction-finders
21. Interference, &c.
22. Direction-finders installed before 26 June, 1959
23. Direction-finders installed before the commencement of these
Regulations
THE SCHEDULES
FIRST SCHEDULE
Direction-Finder
SECOND SCHEDULE
Climatic and Durability Tests
THIRD SCHEDULE
Certificate of Calibration of Direction-Finder
FOURTH SCHEDULE
Record of check-bearings taken by means of the
Direction-Finder
FIFTH SCHEDULE
Alternative requirements for Direction-Finders installed before
the commencement of these Regulations
NAVIGATION (DIRECTION-FINDERS) REGULATIONS - SECT. 1.
Citation
1. These Regulations may be cited as the Navigation (Direction- Finders)
Regulations.*1*
NAVIGATION (DIRECTION-FINDERS) REGULATIONS - SECT. 2. Repeal
2. The Navigation (Direction-Finders) Regulations (being Statutory Rules
1959, No. 48) are repealed.
NAVIGATION (DIRECTION-FINDERS) REGULATIONS - SECT. 3.
Interpretation
Sub-reg. (1) amended by 1982 No. 14 r.1
3. (1) In these Regulations, unless the contrary intention appears-
"mile" means nautical mile;
"radio surveyor" means a person, being a person skilled with regard to radio
navigational aids, appointed under section 190 of the Navigation Act 1912-1967
to be a surveyor;
"ship" means a ship of not less than one thousand six hundred tons that-
(a) is a ship to which Part II of the Navigation Act 1912 applies; or
(b) is engaged in the carriage of passengers from a port in Australia to
a port outside Australia,
* * * * * * *
but does not include-
(d) a Safety Convention ship in respect of which there is in force a
valid Safety Convention certificate showing that the ship-
(i) complies with such of the requirements of the Safety Convention
as relate to radio installations and radio navigational aids; or
(ii) is wholly exempt from those requirements or is partly exempt and
complies with those requirements to the extent to which she is not exempt;
(e) a passenger ship of less than four thousand tons not engaged on
international voyages;
(f) a cargo ship of less than six thousand tons not engaged on
international voyages;
(g) a river and bay ship;
(h) a sailing ship; or
(i) a fishing boat.
(2) In these Regulations-
(a) a reference to the tonnage of a ship shall be read as a reference to
the gross registered tonnage of that ship;
(b) a reference to a Schedule shall be read as a reference to a Schedule to
these Regulations;
(c) a reference to a wave or signal of type A1 shall be read as a reference
to radiotelegraphy by the keying of a continuous wave on and off; and
(d) a reference to a wave or signal of type A2 shall be read as a reference
to amplitude modulated radiotelegraphy by the keying of a modulating
audio-frequency or of an emission continuously modulated by an
audio-frequency.
NAVIGATION (DIRECTION-FINDERS) REGULATIONS - SECT. 4.
Exemptions
4. The Minister may exempt a ship from all or any of the requirements of
these Regulations, either unconditionally or subject to such conditions as the
Minister thinks fit.
NAVIGATION (DIRECTION-FINDERS) REGULATIONS - SECT. 5.
Ships to be provided with directionfinders
5. Subject to these Regulations, a ship shall be provided with a
direction-finder in accordance with these Regulations.
NAVIGATION (DIRECTION-FINDERS) REGULATIONS - SECT. 6.
Requirements for directionfinders
6. (1) A direction-finder shall-
(a) comply with the requirements specified in the First Schedule; and
(b) be such that-
(i) when undergoing the vibration, dry heat and low temperature tests
in accordance with the Second Schedule;
(ii) when subjected to the damp heat test in accordance with that
Schedule; and
(iii) immediately after undergoing, in accordance with that Schedule,
such other tests specified in that Schedule as are applicable,
it complies with the requirements of items 4 and 5 and 8 to 24 (inclusive)
of the First Schedule and is free from mechanical defects.
(2) The loop aerial system forming part of a direction-finder shall be such
that, after undergoing the mould growth test in accordance with the Second
Schedule, mould growth is not present on it.
(3) A direction-finder shall be capable of efficiently determining radio
bearings at all times while the ship in which it is installed is at sea
notwithstanding such interference or mechanical noise as is produced by the
direction-finder.
NAVIGATION (DIRECTION-FINDERS) REGULATIONS - SECT. 7.
Installation of directionfinders
7. (1) A direction-finder shall be installed in a ship in such a position
and manner that efficient determination of radio bearings by means of the
direction-finder is not hindered by extraneous noises or interference at any
time while the ship is at sea.
(2) The loop aerial system forming part of a direction-finder shall be so
mounted that the efficient determination of radio bearings by means of the
direction-finder is hindered as little as possible by the proximity of
aerials, derricks, wire halyards and other large metal objects.
(3) The feeder cables connecting the loop aerial system with the receiver
forming part of a direction-finder shall, unless they consist of
solid-dielectric screened cable, be protected by metal tubes that are bonded
to earth.
(4) The joints of the feeder cables shall be watertight.
NAVIGATION (DIRECTION-FINDERS) REGULATIONS - SECT. 8.
Broadcast receiver aerials
8. (1) Where the aerial of a broadcast receiver on a ship in which a
direction-finder is installed after the commencement of these Regulations
rises above the base of the aerial of the direction-finder, the aerial of the
broadcast receiver shall-
(a) form part of a communal aerial system;
(b) be more than fifty feet from the aerial of the direction-finder; or
(c) be capable of being lowered quickly and stowed easily when the
direction-finder is in use.
(2) In this regulation, "broadcast receiver" means an appliance capable of
being used for the reception, by means of wireless telegraphy, of broadcasting
or television programmes.
NAVIGATION (DIRECTION-FINDERS) REGULATIONS - SECT. 9.
Supply of electrical energy
9. (1) Batteries or some other source of electrical energy sufficient for
the operation of the direction-finder shall be available on the ship for that
purpose.
(2) Where batteries are provided as a source of electrical energy for the
operation of a direction-finder, equipment shall be provided on board the ship
for charging those batteries and the ship's main source of electrical energy
shall be available for that purpose.
NAVIGATION (DIRECTION-FINDERS) REGULATIONS - SECT. 10.
Protection of high voltage parts
10. Parts and wiring of a direction-finder that at any time are at an
instantaneous voltage (excluding radio-frequency voltage) exceeding fifty
volts-
(a) shall be protected from accidental access; and
(b) in the case of parts or wiring (other than a generator or a converter)
that at any time are at an instantaneous voltage exceeding two hundred and
fifty volts-shall be isolated automatically from all sources of electrical
energy when the means of protection are removed.
NAVIGATION (DIRECTION-FINDERS) REGULATIONS - SECT. 11.
Means of communication
11. (1) An efficient two way means of calling and voice communication shall
be provided in every ship between the receiver forming part of the
direction-finder and the bridge from which the ship is normally navigated.
(2) An efficient means of signalling shall be provided between the receiver
forming part of the direction-finder and the ship's standard compass or gyro
compass repeater, if any.
NAVIGATION (DIRECTION-FINDERS) REGULATIONS - SECT. 12.
Wiring diagram and instructions
12. A schematic wiring diagram of the direction-finder on a ship, and a book
containing adequate instructions as to the use of the direction-finder, shall
be provided on board the ship and shall be available at all times for use by a
person operating or testing the direction-finder.
NAVIGATION (DIRECTION-FINDERS) REGULATIONS - SECT. 13.
Maintenance of directionfinders
13. A direction-finder installed in a ship shall be maintained so that it
is, at all times while the ship is at sea, capable of efficiently determining
radio bearings.
NAVIGATION (DIRECTION-FINDERS) REGULATIONS - SECT. 14.
Calibration
Sub-reg. (1) amended by 1969 No. 144 r. 1
14. (1) A direction-finder in a ship shall, as soon as practicable and not
later than thirty days after the ship first puts to sea after-
(a) the direction-finder has been installed in the ship;
(b) any change is made in the position of the loop aerial system forming
part of the direction-finder;
(c) any change is made in any structure or fitting on or above the upper
deck within fifty feet of the loop aerial system forming part of the
direction-finder, not being a change that a radio surveyor has certified, in
writing, to be a change that is not likely to affect the accuracy of the
calibration tables or curves; or
(d) any change is made in the electrical characteristics of the loop aerial
system forming part of the direction-finder, not being a change that a radio
surveyor has certified, in writing, to be a change that is not likely to
affect the accuracy of the calibration tables or curves,
be calibrated in accordance with this regulation and adjusted so that readings
taken by it, when corrected with the calibration tables, differ from the
correct bearings by not more than plus or minus two degrees.
(2) A direction-finder shall be calibrated by two persons, one being
experienced in taking radio bearings and the other in taking visual bearings,
in the following manner:
(a) the calibration shall be carried out by taking simultaneously visual
bearings upon a calibrating transmitter and radio bearings upon that
transmitter by means of the direction-finder-
(i) the ship being either swung through a complete circle or circled by
another ship carrying the calibrating transmitter; and
(ii) the bearings being taken throughout three hundred and sixty degrees
at intervals of five degrees or as close to those intervals as is
practicable;
(b) the calibrating transmitter upon which the bearings are taken, whether
it is situated on shore or on board another ship, shall be a transmitter
operating on a frequency of not less than two hundred and eighty-five
kilocycles per second and not more than three hundred and twenty-five
kilocycles per second; and
(c) calibration tables and curves shall be prepared on the basis of the
bearings taken.
NAVIGATION (DIRECTION-FINDERS) REGULATIONS - SECT. 15.
Verification of calibration tables and curves
15. (1) Calibration tables and curves prepared in accordance with the last
preceding regulation shall be verified by means of check bearings taken-
(a) at intervals not exceeding twelve months; and
(b) when a change is made in any structure or fitting on or above the upper
deck of the ship, not being a change that a radio surveyor has certified, in
writing, to be a change that is not likely to affect the accuracy of the
calibration tables or curves-as soon as practicable and not later than thirty
days after the ship first puts to sea after the change has been made.
Amended by 1969 No. 144 r. 2
(2) The check bearings referred to in the last preceding sub-regulation
shall be-
(a) simultaneous radio and visual bearings of a transmitter, being, in the
case of the radio bearings, bearings made on a frequency not lower than two
hundred and fifty-five kilocycles per second and not higher than five hundred
and twenty-five kilocycles per second; or
(b) simultaneous radio and calculated bearings of a transmitter in a known
position, being-
(i) in the case of the radio bearings, bearings made on a frequency not
lower than two hundred and fifty-five kilocycles per second and not higher
than five hundred and twenty-five kilocycles per second; and
(ii) in the case of the calculated bearings, bearings calculated by the
master or a mate of the ship who, for the purposes of the calculation, has
determined the position of the ship by visual bearings of known points.
(3) If the verification made in accordance with this regulation shows that
the calibration tables or curves are materially inaccurate, the
direction-finder shall, as soon as practicable, be recalibrated in the manner
specified in the last preceding regulation.
NAVIGATION (DIRECTION-FINDERS) REGULATIONS - SECT. 16.
Records of calibration and verification
16. There shall be kept on board a ship, in a place accessible to a person
operating the direction-finder on the ship-
(a) a list or diagram indicating the condition and position, on the most
recent occasion on which the direction-finder was calibrated, of the aerials,
and all movable structures, on board the ship that might affect the accuracy
of the direction-finder;
(b) the calibration tables and curves which were prepared on the most
recent occasion on which the direction-finder was calibrated;
(c) a certificate of calibration, in accordance with the form specified in
the Third Schedule, relating to the most recent occasion on which the
direction-finder was calibrated, and signed by the persons making the
calibration; and
(d) a record, in accordance with the form specified in the Fourth Schedule,
of check bearings taken for the verification of calibration, the bearings
being numbered in the order in which they were taken.
NAVIGATION (DIRECTION-FINDERS) REGULATIONS - SECT. 17.
Master to make calibration records available to radio surveyor
17. The master of a ship shall make the list or diagram, calibration tables
and curves, certificate of calibration and record required by the last
preceding regulation to be kept on the ship available, at all reasonable
times, to a radio surveyor for inspection.
Penalty: Two hundred dollars.
NAVIGATION (DIRECTION-FINDERS) REGULATIONS - SECT. 18.
Charging of batteries
18. The master of a ship shall cause batteries provided as a source of
electrical energy for the direction-finder on the ship to be tested once each
day by voltmeter and once each month by hydrometer, and shall cause a battery
which is found not to be fully charged to be fully charged as soon as
practicable.
Penalty: Two hundred dollars.
NAVIGATION (DIRECTION-FINDERS) REGULATIONS - SECT. 19.
Supply of electrical energy for testing
19. The master of a ship shall cause a sufficient supply of electrical
energy for testing the direction-finder on the ship to be available at all
reasonable times while the ship is in port.
Penalty: Two hundred dollars.
NAVIGATION (DIRECTION-FINDERS) REGULATIONS - SECT. 20.
Use of direction-finders
20. A direction-finder on a ship shall not be used-
(a) for a purpose other than the business of the ship; or
(b) for keeping the radio watch required to be kept by the Navigation
(Radio) Regulations.
NAVIGATION (DIRECTION-FINDERS) REGULATIONS - SECT. 21.
Interference, &c.
21. The master of a ship shall not, while the ship is at sea, permit the
occurrence of noise or interference on the ship likely to hinder the efficient
determination of radio bearings by the direction-finder on the ship.
Penalty: Two hundred dollars.
NAVIGATION (DIRECTION-FINDERS) REGULATIONS - SECT. 22.
Direction-finders installed before 26 June, 1959
22. (1) Sub-regulations (1) and (2) of regulation 6 of these Regulations do
not apply to or in relation to a direction-finder that-
(a) has been installed before the twenty-sixth day of June, 1959;
(b) complies with the requirements of Article 47 and paragraph 17 of
Article 31 of the International Convention for the Safety of Life at Sea
signed in London on the thirty-first day of May, 1929; and
(c) is capable of-
(i) receiving waves of type A1 and type A2 on all frequencies from and
including two hundred and fifty-five kilocycles per second to and including
five hundred and twenty-five kilocycles per second; and
(ii) taking radio bearings when the field strength at the loop aerial
system is as low as fifty microvolts per metre.
(2) This regulation ceases to have effect on and after the first day of
January, 1969.
NAVIGATION (DIRECTION-FINDERS) REGULATIONS - SECT. 23.
Direction-finders installed before the commencement of these Regulations
23. Sub-regulations (1) and (2) of regulation 6 of these Regulations do not
apply to or in relation to a direction-finder that has been installed before
the commencement of these Regulations if-
(a) the direction-finder complies with the requirements of the Fifth
Schedule; or
(b) the direction-finder-
(i) has been installed on or after the twenty-sixth day of June, 1959;
(ii) complies with the requirements of regulation 11 of Chapter IV of
the International Convention for the Safety of Life at Sea, 1960; and
(iii) is capable of receiving waves of type A1 and type A2 on all
frequencies from and including two hundred and fifty-five kilocycles per
second to and including five hundred and twenty-five kilocycles per second.
-----------
NAVIGATION (DIRECTION-FINDERS) REGULATIONS - SCHEDULE 1
SCH
THE SCHEDULES
FIRST SCHEDULE
Regulation
6
DIRECTION-FINDER
General
1. For the purposes of this Schedule-
(a) "locally generated signals" means signals obtained from a signal
generator or signal generators;
(b) a goniometer forming part of a direction-finder shall, except for the
purposes of item 17 of this Schedule, be deemed to be part of the
direction-finding aerial system; and
(c) "signal to noise ratio" means the ratio of the signal plus noise to the
noise alone.
2. The direction-finder shall include a receiver, a direction-finding
aerial
system and any other equipment required to enable the radio bearing and sense
of the signal to be determined.
3. The mechanical parts of the direction-finding aerial system, other than
ball bearings, hose clips, set screws and other similar small parts, shall
consist of non-magnetic material.
Capability
4. (1) The direction-finder shall be capable of headphone reception of
waves
of type A1 and type A2 of any frequency within the range 255 kilocycles per
second to 525 kilocycles per second so as to enable the radio bearing and
sense
of the signal to be determined by aural-null or other means.
(2) The direction-finder shall be capable of operation within one minute of
its being connected to a source of energy.
Controls
5. The direction-finder shall be provided with-
(a) a manual control for the adjustment of radio frequency gain or
intermediate frequency gain or both;
(b) a manual control for the adjustment of audio frequency gain;
(c) means of audio monitoring for any method that may be used for
direction
finding;
(d) a tuning control;
(e) a tuning scale that is calibrated directly in frequency and in which,
at
no point in the tuning range, an interval of 1/8 inch corresponds to a
frequency change of more than 8 kilocycles per second; and
(f) where the direction-finder incorporates a loud speaker-means to make
the
loud speaker inoperative.
Power Supply
6. (1) The direction-finder shall, unless otherwise specified, be capable
of
complying with the requirements of this Schedule for a range of voltage
variation of plus or minus 10 per centum relative to the nominal supply
voltage.
(2) Where the direction-finder is capable of operation from more than one
source of energy, means shall be provided for changing the direction-finder
quickly from one source of energy to another.
(3) Neither vibrators nor dry cells shall be incorporated in the
direction-finder or in any source of electrical energy for the
direction-finder.
General Method of Testing
7. The receiver shall, unless otherwise specified, comply with the
requirements of items 8 to 21 (inclusive) of this Schedule when tested in the
following manner on any frequency within the range 255 kilocycles per second
to
525 kilocycles per second:
(a) locally generated signals shall be injected through a network in such
a
manner that the signal generator or generators, as the case may be, and the
network are together equivalent to a constant voltage zero impedance
generator
in series with an impedance substantially equal to the impedance of the
direction-finding aerial system at the test frequency when-
(i) the direction-finding aerial system is adjusted for the
determination of radio bearings;
(ii) the sense-finder is not in operation; and
(iii) the impedance is measured between the two terminals to which the
receiver is normally connected;
(b) the effective height (h^e^) in metres of the direction-finding aerial
system shall be the ratio E/e, where "E" is the voltage produced by a
vertically polarized field of strength "e" volts per metre when-
(i) the direction-finding aerial system is adjusted for the
determination of bearings and for maximum pick-up;
(ii) the sense-finder is not in operation;
(iii) the receiver is not connected to the direction-finding aerial
system; and
(iv) the voltage is measured between the terminals of the
direction-finding aerial system to which the receiver is normally connected;
(c) the standard input level shall be the input level obtained when the
electromotive force of the equivalent signal generator referred to in
paragraph
(a) of this item is 50h^e^ microvolts root mean square;
(d) the standard output level shall be-
(i) for headphone reception, an audio-frequency output of 1 milliwatt
into a resistance substantially equal to the modulus of the impedance of the
telephone receivers at 400 cycles per second; and
(ii) for loud-speaker reception, an audio-frequency output of 50
milliwatts into a resistance substantially equal to the modulus of the
impedance of the loudspeaker at 400 cycles per second;
(e) a type A2 test signal shall, unless otherwise specified, be modulated
to
a depth of 30 per centum by a signal of 400 cycles per second; and
(f) the automatic gain control, if any, shall, unless otherwise specified,
be inoperative.
Signal and Intermediate Frequency Selectivity
8. (1) The signal frequency selectivity of the receiver or, in the case of
a
superheterodyne receiver, the signal and intermediate frequency selectivity
shall satisfy the following requirements:
(a) the minimum bandwidth for 6 decibels discrimination shall be 2
kilocycles per second;
(b) the maximum bandwidth in relation to discrimination shall be in
accordance with the following table:
------------------------------------------------------------------------
The discrimination
shall
Where the maximum bandwidth is- be not less than-
------------------------------------------------------------------------ 8
kilocycles per second . . . . . . . . . . . 30 decibels
16 kilocycles per second . . . . . . . . . . . 60 decibels
35 kilocycles per second . . . . . . . . . . . 90 decibels
------------------------------------------------------------------------ (c)
at a frequency outside the bandwidth of plus and minus twenty kilocycles
per second the discrimination-
(i) shall be not less than ninety decibels except at the image
frequency
in superheterodyne receivers; and
(ii) shall be not less than eighty decibels at the image frequency in
superheterodyne receivers.
(2) In testing non-aural null type equipment for the purposes of this item,
the automatic gain control shall be inoperative.
Gain
9. The gain of the receiver shall be such that, when-
(a) the input terminals of the receiver are closed solely through an
external impedance substantially equal to that of the direction-finding aerial
system at
the test frequency;
(b) the receiver is in the condition for reception of signals of type A1;
(c) the sense-finder is not in operation; and
(d) impedance is measured between the two terminals of the
direction-finding
aerial system to which the receiver is normally connected,
receiver noise can produce an output level of minus 10 decibels relative to
the
standard output level at any frequency within the range of frequencies
specified in item 4 of this Schedule.
Signal to Noise Ratio
10. (1) When-
(a) the note filter, if any, is switched out of circuit;
(b) a signal of type A1 or type A2 of standard input level is injected
into
the receiver; and
(c) the receiver gain is adjusted manually to give standard output,
the signal to noise ratio shall be not less than the value determined in
accordance with the following table:
------------------------------------------------------------------------------
--
Type of signal Ratio-Aural-null type equipment Ratio-other
equipment
------------------------------------------------------------------------------
-- A1 . . . . . . . . 20 decibels 15 decibels
A2 . . . . . . . . 10 decibels 6 decibels
------------------------------------------------------------------------------
-- (2) For the purposes of this item, spurious whistles shall be regarded
as
noise.
Blocking
11. The change in output of the receiver shall not exceed 3 decibels when-
(a) the receiver is adjusted to give standard output with an input wanted
signal of type A2 at a level of 50 decibels above the standard input level
and
of any frequency in the range specified in item 4 of this Schedule; and
(b) a signal of type A1 is applied simultaneously, the signal being at a
level of 85 decibels above the standard input level and at a frequency 10
kilocycles per second above or below that of the wanted signal.
Linearity
12. (1) With the receiver adjusted to give standard output with an input
signal of type A1 at a level 20 decibels above standard input level, the
input-output characteristic shall be such that any increase of input level to
a
level not more than 60 decibels above the standard input level shall not cause
a diminution of output level below that required for a straight
characteristic
exceeding 1 decibel relative to maximum output level.
(2) With the receiver adjusted to give standard output with an input signal
of type A1 at a level 40 decibels above standard input level, the
input-output
characteristic shall be such that any increase of input level to a level not
more than 60 decibels above the standard input level shall not cause a
diminution of output level below that required for a straight characteristic
exceeding 1 decibel relative to maximum output level.
Intermodulation
13. The output level of the receiver shall not exceed the standard output
when-
(a) the receiver is adjusted to give standard output level with an input
wanted signal of type A2 at standard input level and at any frequency
specified
in item 4 of this Schedule;
(b) the input wanted signal has been removed; and
(c) any two unwanted locally generated signals-
(i) each of which is at a level 70 decibels above standard input level
and of a frequency not less than 50 kilocycles per second from the frequency
of
the wanted signal; and
(ii) one of which is of type A1 and the other of type A2,
are applied simultaneously.
Harmonic Production
14. The output level of the receiver shall not exceed the standard output
when-
(a) the receiver is adjusted to give standard output level with an input
wanted signal of type A2 at standard input level and at the frequency of 500
kilocycles per second;
(b) the input wanted signal has been removed; and
(c) a type A2 signal that is-
(i) of a frequency that is any sub-harmonic of 500 kilocycles per
second; and
(ii) at a level of 80 decibels above the standard input level,
is applied to the receiver.
Fidelity
15. (1) The maximum change in level of the output of the receiver shall be
less than 8 decibels when the modulating frequency of an input signal that
is-
(a) of any frequency in the range specified in item 4 of this Schedule;
and
(b) of constant level and modulation depth, not being a level or depth
that
causes the output of the receiver to exceed the standard output level,
is varied continuously from 300 cycles per second to 1,350 cycles per second.
(2) For the test referred to in the last preceding sub-item in relation to
equipment that is not aural-null type equipment, the receiver shall be set
for
the reception of waves of type A2.
Radiation
16. The direction-finder shall not in normal service produce a field
exceeding 0.1 microvolt per metre when measured at a distance of 1 nautical
mile from the
receiver.
17. The direction-finder shall be deemed to comply with the last preceding
item, if, when-
(a) the receiver, with the goniometer (if any) but without the aerial
system, is placed centrally in a screened earthed enclosure at least 6 feet
cube;
(b) the earth terminal is connected to the inside of the screen;
(c) each aerial terminal in turn is connected through an unscreened 4-turn
rectangular search coil, 1 foot square, situated within the enclosure and an
unscreened lead to a resistive measuring instrument mounted outside the
enclosure and having its other terminal earthed;
(d) the aerial terminal or terminals of the receiver, other than the
terminal connected to the measuring instrument, are earthed one at a time or
in any
combination or remain unearthed or are interconnected in any combination; and
(e) the receiver is energized and unscreened headphones are connected to
it,
the power measured by the measuring instrument, connected in the manner
specified in paragraph (c) of this item, does not exceed 4 x 10-^10^ watt
whatever the resistance of the measuring instrument or the adjustment of the
receiver and whether or not the search coil is short-circuited or moved in
any
way other than a way that causes it to approach within six inches of the
receiver case.
Tuning Drift and Stability
18. After the receiver has been switched on for 5 minutes and tuned to any
frequency within the frequency range specified in item 4 of this Schedule,
the
tune frequency shall not change by more than 5 parts in 10,000 in any period
of
5 minutes.
19. A change of 5 per centum in any one of the supply voltages to the
receiver, or to a power unit associated with the supply voltages, shall not
cause the tune frequency to change by more than 3 parts in 10,000.
20. A change of ambient temperature of 5 degrees Centigrade within the range
0 degrees Centigrade to 50 degrees Centigrade applied after the receiver has
been
switched on for one hour shall not cause the tune frequency to change by more
than 1 part in 1,000.
Heterodyne Note Stability
21. The heterodyne note stability of the receiver shall be such that-
(a) the frequency of a heterodyne note that is initially 1 kilocycle per
second shall not vary by more than 100 cycles per second when an input signal
is increased over a range of levels from 0 to 60 decibels above the standard
input; and
(b) at all levels within the range specified in the last preceding
paragraph, a beat note of 200 cycles per second can be obtained by tuning
either towards or away from zero beat.
Bearing Indicator Scales
22. (1) If the direction-finder includes a circular bearing indicator
scale-
(a) the scale shall be marked at intervals of one degree with a mark of
one
of three different kinds, one kind being used for each tenth mark, another
kind
for each fifth mark, not being a tenth mark, and the third kind for all other
marks;
(b) each tenth mark on the scale shall be numbered to indicate the number
of
the degrees that it is intended to denote;
(c) the interval between marks on the scale shall be big enough to make it
possible to read a bearing to at least 0.25 degree; and
(d) the bearing indicator shall not obscure more than 0.5 of a degree of
the
scale.
(2) If the equipment includes a digital display for the bearing indicator-
(a) the display shall be easily readable; and
(b) it shall be possible to read bearings to at least 0.25 degree.
Aural-Null Type Direction-Finders
23. (1) This item applies in relation to direction-finders suitable for
determining bearings by aural-null means.
(2) The bearings indicated by the scale of the direction-finder, due
allowance being made for site errors and the previous setting of the indicator
being
disregarded, shall, at all frequencies in the range of frequencies specified
in
item 4 of this Schedule, throughout the whole 360 degrees of azimuth, be
correct within plus or minus one degree of the correct bearing when the
direction-finder is tested using-
(a) waves of type A2 modulated to a depth of from 80 per centum to 100 per
centum; and
(b) waves of type A1,
with a substantially vertically polarized field having a field strength of 40
decibels above 1 microvolt per metre.
(3) A change in the setting of the bearing indicator of the
direction-finder
of 5 degrees or 90 degrees in either direction from the position or any of
the
positions of minimum output shall, at all frequencies in the range of
frequencies specified in item 4 of this Schedule, cause the audio-frequency
output to increase by not less than 18 decibels or 35 decibels, as the case
may
be, when the direction-finder is arranged for the taking of bearings and is
tested under the conditions specified in the last preceding sub-item but
with-
(a) a field strength sufficient to give a signal to noise ratio of not
less
than 50 decibels with the direction-finding aerial system adjusted for
maximum
output; and
(b) any minimum clearing control in the same position as it was when the
direction-finder was tested under the last preceding sub-item.
(4) The audio-frequency output level of the receiver due to the wanted
signal
shall, when-
(a) the direction-finder is adjusted for the determination of sense, and
is
tested under the conditions specified in sub-item (2) but with a field
strength
sufficient to give a signal to noise ratio of not less than 50 decibels with
the direction-finding aerial system adjusted for maximum output; and
(b) the sense indicator is adjusted to indicate any bearing within plus or
minus 10 degrees of the correct bearing,
be not less than 20 decibels below the output level that is obtained when the
sense indicator is adjusted to indicate a bearing within 180 degrees, plus or
minus 10 degrees, of the correct bearing.
Other Types of Direction-Finders
24. (1) This item applies in relation to direction-finders suitable for
determining bearings by other than aural-null means.
(2) The direction-finder shall include a device to indicate that the
receiver
gain and signal strength are sufficient to enable a correct bearing to be
taken.
(3) When the direction-finder is tested throughout the whole 360 degrees of
azimuth at all frequencies in the range of frequencies specified in item 4 of
this Schedule with a substantially vertically polarized field using a signal
of
a type set out in column 1 of the following table and of a field strength set
out in column 2 of that table opposite to that type-
(a) the bearings indicated by the scale or display of the direction-finder
shall not, due allowance being made for site errors and the previous
indicated
bearing being disregarded, differ from the correct bearing by more than the
number of degrees shown in column 3 of that table; and
(b) the fluctuations in the indicated bearing shall not, due allowance
being
made for site errors and the previous indicated bearing being disregarded,
exceed the values shown in column 4 of that table,
opposite to the type and field strength of the signal set out in columns 1 and
2 of that table.
------------------------------------------------------------------------------
--
Column 1 Column 2 Column 3 Column 4
Maximum
fluctuation
Type of signal Field strength Maximum error from mean
bearing
------------------------------------------------------------------------------
-- A2 modulated to a
depth of 80 to 100
per centum 40 decibels above 1
microvolt per metre Plus or minus 1
degree Plus or minus
0.5 degree
A1 . . . . . . . . . 40 decibels above 1
microvolt per metre Plus or minus 1
degree Plus or minus
0.5 degree
A2 modulated to a
depth of 80 to 100
per centum 100 decibels above 1
microvolt per metre Plus or minus 1
degree Plus or minus
0.5 degree
A1 . . . . . . . . . 100 decibels above 1
microvolt per metre Plus or minus 1
degree Plus or minus
0.5 degree
A2 modulated to a
depth of 80 to 100
per centum 30 decibels above 1
microvolt per metre Plus or minus 2
degrees Plus or minus
1
degree
A1 . . . . . . . . . 30 decibels above 1
microvolt per metre Plus or minus 2
degrees Plus or minus
1
degree
------------------------------------------------------------------------------
-- (4) When-
(a) the direction-finder is adjusted for the reception of a wanted signal
of
any frequency in the range specified in item 4 of this Schedule and of field
strength 40 decibels above one microvolt per metre or of 6 decibels above
standard input level; and
(b) there is applied simultaneously a second signal-
(i) that is an unwanted signal of the same type as, and from a source
90
degrees from that of, the wanted signal;
(ii) in respect of which the frequency separation in relation to the
wanted signal is equal to a frequency separation specified in column 1 of the
following table; and
(iii) in respect of which the field strength or equivalent input level
is
the strength or level, as the case may be, specified in column 2 or column 3,
as the case may be, of that table opposite to the frequency separation in
column 1
referred to in the last preceding sub-paragraph,
the change in indicated bearing shall not exceed one degree.
------------------------------------------------------------------------------
--
Column 1 Column 2 Column 3
Frequency separation
in
kilocycles per
second Field strength Equivalent input level
------------------------------------------------------------------------------
-- Plus or minus 1 . . 30 decibels above 1
microvolt per metre 4 decibels below
standard
input
Plus or minus 4 . . 60 decibels above 1
microvolt per metre 26 decibels above
standard input
Plus or minus 20 . . 100 decibels above 1
microvolt per metre 66 decibels above
standard input
------------------------------------------------------------------------------
-- (5) The equipment shall comply with the provisions of the last preceding
sub-item notwithstanding that both signals are of type A1 or both are of type
A2.
(6) The indicated bearing shall not change by more than 1 degree when, with
an input signal with a field strength of 60 decibels above 1 microvolt per
metre or a signal 26 decibels above standard input level and the automatic
gain control,
if fitted, operative, the receiver is mistuned until either-
(a) the audio frequency output falls by 6 decibels; or
(b) the device referred to in sub-item (2) of this item shows that the
signal has fallen to the minimum at which a bearing can be taken,
whichever first occurs.
(7) With the equipment adjusted for taking bearings and with the ratio of
signals as specified by the manufacturer applied to the direction-finding and
sense paths, an increase or decrease of 10 decibels in sense level shall not-
(a) where sense finding is not a separate operation-change the indicated
bearing by more than 1 degree; or
(b) where sense finding is a separate operation-leave any ambiguity of
sense.
(8) When, with the bearing indicator in any rest position, a signal
simulating one from a bearing of 175 degrees from that indicated by the rest
position is
applied at any and every level in the range between 6 and 60 decibels above
standard input level-
(a) a new indicated bearing within 1 degree of the correct bearing shall
be
obtained within two seconds at room temperature and within four seconds at
minus 15 degrees Centigrade; and
(b) without further adjustment of the equipment or signal source, the
indicated bearing shall remain within 1 degree of the correct bearing during
a
further twenty seconds.
(9) There shall be no observable change of indicated bearing when the beat
frequency oscillator is switched on, whether or not the signal is of a
strength
sufficient to give a bearing indication.
(10) It shall be possible to make, in not more than 10 seconds after
identifying a station the bearing of which is required, any check or
adjustment
of any control that is necessary as part of the process of direction-finding.
Additional Safeguards to be Incorporated where the Equipment includes
Semi-conductor Devices
25. Where semi-conductor devices are incorporated in the equipment-
(a) the maker's maximum ratings for each type of semi-conductor device
shall
not be disregarded and, in particular, the recommended junction temperature
shall not be exceeded;
(b) adequate screening and filtering shall be provided to protect the
devices from damage due to radio frequency energy; and
(c) the devices shall be effectively protected from damage due to-
(i) transient changes in power supply voltage;
(ii) accidental reversal of power supply polarity; or
(iii) a sustained increase in power supply voltage of 25 per centum or
more, relative to the nominal battery voltage when the equipment is operated
from a battery of secondary cells.
----------
NAVIGATION (DIRECTION-FINDERS) REGULATIONS - SCHEDULE 2
SCH
SCHEDULE 2
Regulation
6
CLIMATIC AND DURABILITY TESTS
General
1. In this Schedule-
(a) a reference to Class B equipment shall be read as a reference to parts
of the direction-finder other than the loop aerial system; and
(b) a reference to Class X equipment shall be read as a reference to the
loop aerial system of the direction-finder.
2. (1) Subject to this item-
(a) Class B equipment shall be subjected to the tests specified in column
1
of the table in this sub-item; and
(b) Class X equipment shall be subjected to the tests specified in column
2
of that table,
in the order indicated by the numbers preceding the references to those tests
in those columns.
------------------------------------------------------------------------------
--
Column 1 Column 2
Tests to which Class B Equipment Tests to which Class X Equipment
to be subjected to be subjected
------------------------------------------------------------------------------
-- 1 Vibration test 1 Vibration test
2 Bump test 2 Bump test
3 Dry heat test 3 Dry heat test
4 Damp heat test 4 Damp heat test
5 Low temperature test 5 Low temperature test
6 Corrosion test (salt water) 6 Rain test
7 Corrosion test (acid fumes) if a
battery is included in the equipment 7 Immersion test
8 Corrosion test (salt water)
9 Corrosion test (acid fumes) if a
battery is included in the
equipment
10 Mould growth test
------------------------------------------------------------------------------
-- (2) Class X equipment that has been subjected to the rain test at a
static
pressure of not less than 45 pounds per square inch or more than 55 pounds
per
square inch shall not be subjected to the immersion test.
(3) Where the provisions of this Schedule require the equipment to be kept
working for the purposes of any test, power shall be supplied to the
equipment
at the voltage at which the equipment is intended to be operated.
3. The tests referred to in the last preceding item shall be conducted in
accordance with the succeeding provisions of this Schedule.
Vibration Test
4. The equipment, complete with its chassis covers and shock absorbers (if
any), and in its normal operating position, shall be clamped to a vibration
table.
5. The table shall be vibrated at all frequencies between 0 and 12.5 cycles
per second at an amplitude of plus and minus 0.16 centimetre while the
equipment is kept working continuously.
6. The table shall be so vibrated for 3 periods each of 8 minutes'
duration.
7. The direction of the vibration during each period referred to in the
last
preceding item shall be perpendicular to the direction of the vibrations
during
the other two periods.
Bump Test
8. The equipment shall be subjected to not less than 500 bumps at a
constant
rate, not being less than 1 bump or more than 4 bumps per second, with a free
drop of at least 2.5 centimetres.
Dry Heat Test
9. Class X equipment shall be placed in a chamber which is maintained for a
period of 10 hours at a constant temperature of 70 degrees Centigrade, within
a
tolerance of plus or minus 1 degree Centigrade.
10. The chamber shall then be cooled to a constant temperature of 55
degrees
Centigrade, within a tolerance of plus or minus 1 degree Centigrade, and the
direction-finder shall be kept working continuously at that temperature for a
period of 2 hours.
Damp Heat Test
11. The equipment shall be placed in a chamber which shall, within a period
not exceeding 2 hours, be heated from room temperature to 40 degrees
Centigrade
and brought to a relative humidity of not less than 95 per centum.
12. The chamber shall be kept at a temperature of 40 degrees Centigrade,
within a tolerance of plus or minus 1 degree Centigrade, for a period of 12
hours, and at a relative humidity of not less than 95 per centum.
13. At the beginning of the last hour of the period of 12 hours, all
accessible surfaces and components shall be wiped dry and any fans or drying
lamps provided in the equipment shall be switched on.
14. After the fans or drying lamps have been in operation for 30 minutes
and
while the temperature of the chamber is still 40 degrees Centigrade, within a
tolerance of plus or minus 1 degree Centigrade, the equipment shall be
operated
and checked.
15. The temperature of the chamber shall then, in preparation for the low
temperature test, be allowed to fall below 25 degrees Centigrade, the
equipment
being retained in the chamber.
Low Temperature Test
16. Class B equipment shall be exposed to a temperature of minus 15 degrees
Centigrade, within a tolerance of plus or minus 1 degree Centigrade, at
normal
atmospheric pressure, for a period of not less than 12 hours.
17. Class X equipment shall be exposed to a temperature of minus 25 degrees
Centigrade, within a tolerance of plus or minus 1 degree Centigrade, at
normal
atmospheric pressure for a period of not less than 12 hours.
Rain Test
18. The equipment shall be placed in a chamber fitted with 8 shower heads,
the discharge end of each of which consists of a flat, non-rustable metal
plate,
0.16 centimetre thick, having 36 holes each of 0.1 centimetre diameter evenly
spaced in concentric circles in the following manner:
16 holes on the periphery of a circle of 5.1 centimetres diameter.
8 holes on the periphery of a circle of 3.8 centimetres diameter.
8 holes on the periphery of a circle of 2.5 centimetres diameter.
4 holes on the periphery of a circle of 1.3 centimetres diameter.
19. The shower heads shall be arranged at a distance of not less than 50
centimetres and not more than 80 centimetres from the equipment in such a
manner that spray from 4 of the shower heads is directed downwards at an angle
of 45
degrees at each of the four uppermost corners of the equipment, and the spray
from the other 4 shower heads is directed horizontally at the centre of each
area of the four sides of the equipment.
20. Fresh water at room temperature and at a static pressure-
(a) not being less than 15 pounds per square inch or more than 25 pounds
per
square inch, if the equipment is to be subjected to the immersion test; or
(b) not being less than 45 pounds per square inch or more than 55 pounds
per
square inch, in any other case,
shall be sprayed on the equipment from the shower heads for a period of 1
hour,
the equipment being in the position in which it is normally operated.
21. The equipment shall, throughout the test, be rotated at not less than
12
and not more than 20 revolutions per minute about a vertical axis passing
through the centre of the equipment.
Immersion Test
22. The equipment, in the condition in which it will normally be kept on
board ship, shall be immersed in water the surface of which is at least 10
centimetres above the highest point of the equipment, and shall remain so
immersed for a
period of 1 hour.
23. Upon its removal from the water the equipment shall be drained of
water.
Corrosion Test (Salt Water)
24. The equipment shall be placed in a chamber fitted with apparatus
capable
of spraying in the form of a fine mist either natural sea water, or water
which
contains, within a tolerance of plus or minus 10 per centum, the following
percentages of salts in solution:
Salt Percentage
Sodium Chloride . . . . . . . . . . . . . . . . . . . . 2.7
Magnesium Chloride . . . . . . . . . . . . . . . . . . . 0.6
Calcium Chloride . . . . . . . . . . . . . . . . . . . . 0.1
Potassium Chloride . . . . . . . . . . . . . . . . . . . 0.07
25. The spraying apparatus shall be such that the products of corrosion
cannot mix with the sea water or solution contained in the spray reservoir.
26. The equipment shall be sprayed simultaneously on all its external
surfaces with the sea water or solution for a period of 1 hour and shall be
kept working
continuously for the second 30 minutes of that hour.
27. The equipment shall, immediately after the expiration of the hour, be
stored for a period of 7 days at a temperature of 40 degrees Centigrade,
within
a tolerance of plus or minus 1 degree Centigrade, and at a relative humidity
of
not less than 60 per centum and not more than 80 per centum.
28. The equipment shall be so sprayed and stored on four separate
occasions.
Corrosion Test (Acid Fumes)
29. A battery included in the equipment shall be fully charged and then
fitted into the equipment.
30. If the battery can be charged without being removed from the equipment,
the battery shall continue to be charged at the maximum rate appropriate to
it
for a period of 24 hours.
31. The equipment shall immediately after the expiration of that period be
stored for a period of 4 weeks at a temperature of 40 degrees Centigrade,
within a tolerance of plus or minus 1 degree Centigrade, and at a relative
humidity of
not less than 60 per centum and not more than 80 per centum.
Mould Growth Test
32. The equipment shall be inoculated by spraying with an aqueous
suspension
of mould spores containing the cultures specified in column 1, or the
cultures
specified in column 2, of the following table:
------------------------------------------------------------------------------
--
Column 1 Column 2
------------------------------------------------------------------------------
-- Aspergillus niger Aspergillus niger
Aspergillus amstelodami Aspergillus amstelodami
Paecilomyces varioti Aspergillus versicolor
Stachybotrys atra Stachybotrys atra
Penicillium brevi-compactum Penicillium brevi-compactum
Penicillium cyclopium Cladosporum herbasum
Chaetomium globosum
------------------------------------------------------------------------------
-- 33. Immediately after it has been so sprayed, the equipment shall be
placed in a chamber the temperature of which shall be maintained at a fixed
value not less than 31 degrees Centigrade or more than 33 degrees Centigrade
and controlled to
within a tolerance of plus or minus 1 degree Centigrade at a relative
humidity
of not less than 95 per centum, and shall be kept in the chamber for a period
of 28 days.
----------
NAVIGATION (DIRECTION-FINDERS) REGULATIONS - SCHEDULE 3
SCH
SCHEDULE 3
Regulation 16
(c)
Navigation (Direction-Finders) Regulations
CERTIFICATE OF CALIBRATION OF DIRECTION-FINDER
We, the undersigned, hereby certify that we have this day-
(a) calibrated, in accordance with the Navigation (Direction-Finders)
Regulations, the direction-finder installed in the ship ;
(b) handed to the Master of that ship tables of calibration corrections;
and
(c) adjusted the direction-finder so that the readings taken by it, when
corrected with the tables, differed from the correct bearings by no more than
plus or minus 2 degrees.
We further certify that the Master of the above-mentioned ship has been
furnished with a list or diagram indicating the condition and position, at
the
time of the calibration, of the aerials and of all movable structures on
board
the ship which might affect the accuracy of the direction-finder.
Dated this day of , 19 .
Radio Observer.
Visual Observer.
----------
NAVIGATION (DIRECTION-FINDERS) REGULATIONS - SCHEDULE 4
SCH
SCHEDULE 4
Regulation 16
(d)
RECORD OF CHECK-BEARINGS TAKEN BY MEANS OF THE DIRECTION-FINDER
Name of Ship:
------------------------------------------------------------------------------
--
True
Bearing
Direction-
by Correction
finder True Visual
required
Ship Relative
Bearing
Check
or to
make
Ship's or
place
Bearing
by Calculation
Col.
(13)
Time
Approximate
in or
at Corrected
Ship's
Direction-
(state equal
Serial (Greenwich
Position
Distance
which for Head Half
Ship's
finder
which;
if Col.
(14)
Number
-------- from
Transmitter
Quadrantal
by Total
Convergency
Head (Col.
(8) by
Calculation,
(indicating Signatures of Mean Longitude
Transmitter
Compass
Compass
Corrected
and
state whether
of
Bearing
Date
Time)
Latitude
situated
Error 0 degrees
/360 degrees
Error
Applied
(True)
Col.
(12)) method)
-or+)
observers
(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
(11) (12) (13) (14) (15)
(16)
------------------------------------------------------------------------------
--
------------------------------------------------------------------------------
-
------
NAVIGATION (DIRECTION-FINDERS) REGULATIONS - SCHEDULE 5
SCH
SCHEDULE 5
Regulation
23
ALTERNATIVE REQUIREMENTS FOR DIRECTION-FINDERS INSTALLED BEFORE THE
COMMENCEMENT OF THESE REGULATIONS
General
1. For the purposes of this Schedule-
(a) "locally generated signals" means signals obtained from a signal
generator or signal generators; and
(b) a goniometer forming part of a direction-finder shall, except for the
purposes of item 13 of this Schedule, be deemed to be part of the loop aerial
system.
2. The direction-finder shall include a receiver and a loop aerial system.
3. The loop aerial system, other than ball bearings, hose clips, set screws
and other similar small parts, shall consist of non-magnetic material.
Capability
4. The direction-finder shall be capable of headphone reception of waves of
type A1 and type A2 of any frequency within the range of 255 kilocycles per
second to 525 kilocycles per second so as to enable the radio bearings and
sense of the signal to be determined by reference to its minimum strength.
Controls
5. The receiver shall be provided with-
(a) a radio-frequency gain control;
(b) a tuning control; and
(c) a tuning scale in which, at no point in the tuning range, an interval
of
1/8 inch corresponds to a frequency change of more than 8 kilocycles per
second.
General Method of Testing
6. The receiver shall comply with the requirements of items 7 to 18
(inclusive) of this Schedule when tested in the following manner on any
frequency within the range 255 kilocycles per second to 525 kilocycles per
second:
(a) Locally generated signals shall be injected through a network in such
a
manner that the signal generator or generators, as the case may be, and the
network are together equivalent to a constant voltage generator in series
with
an impedance substantially equal to the impedance of the loop aerial system
at
the test frequency, when-
(i) the loop aerial system is adjusted for the determination of radio
bearings;
(ii) the sense-finder is not in operation; and
(iii) the impedance is measured between the two terminals to which the
receiver is normally connected.
(b) The effective height (h^e^) in metres of the loop aerial system shall
be
the ratio E/e, where "E" is the voltage produced by a vertically polarized
field of strength "e" volts per metre when-
(i) the loop aerial system is adjusted for the determination of
bearings
and for maximum pick-up;
(ii) the sense-finder is not in operation;
(iii) the receiver is not connected to the loop aerial system; and
(iv) the voltage is measured between the terminals of the loop aerial
system to which the receiver is normally connected.
(c) The standard input level shall be the input level obtained when the
electromotive force of the equivalent signal generator referred to in
paragraph
(a) of this item is 50h^e^ microvolts root mean square.
(d) The standard output level shall be an audio-frequency output of 1
milliwatt into a resistance substantially equal to the modulus of the
impedance
of the telephone receivers at 1,000 cycles per second.
(e) The signal-noise ratio of the direction-finder shall be determined
either-
(i) by using vertically polarized waves for transmission of the input
signal, and with the loop aerial system arranged for the determination of
bearings and adjusted for maximum pick-up, but without the sense-finder in
operation; or
(ii) by using locally generated signals applied to the receiver only in
the manner specified in paragraph (a) of this item.
Signal and Intermediate Frequency Selectivity
7. The signal frequency selectivity of the receiver or, in the case of a
superheterodyne receiver, the signal and intermediate frequency selectivity
shall satisfy the following requirements:
(a) The minimum bandwidth for 6 decibels discrimination shall be 2
kilocycles per second.
(b) The maximum bandwidth in relation to discrimination shall be in
accordance with the following table:
------------------------------------------------------------------------
The discrimination
shall
be
Where the maximum bandwidth is- not less than-
------------------------------------------------------------------------ 8
kilocycles per second . . . . . . . . . 30 decibels
16 kilocycles per second . . . . . . . . . 60 decibels
35 kilocycles per second . . . . . . . . . 90 decibels
------------------------------------------------------------------------ (c)
At a frequency outside the bandwidth of 35 kilocycles per second the
discrimination shall not be less than 90 decibels except in the case of
superheterodyne receivers where, at the image frequency, the discrimination
shall not be less than 80 decibels.
Gain
8. The gain of the receiver shall be such that, when-
(a) the input terminals of the receiver are closed solely through an
external impedance substantially equal to that of the loop aerial system at
the test
frequency;
(b) the sense-finder is not in operation; and
(c) impedance is measured between the two terminals of the loop aerial
system to which the receiver is normally connected,
receiver noise can produce an output level of minus 10 decibels relative to
the
standard output level at any frequency within the range of frequencies
specified in item 4 of this Schedule.
Signal-Noise Ratio
9. (1) The signal-noise ratio shall not be less than 20 decibels when-
(a) the note filter (if any) is switched out of circuit;
(b) a signal of type A1 is injected at the standard input level; and
(c) the receiver gain is manually adjusted to give the standard output
level.
(2) The signal-noise ratio shall not be less than 10 decibels when-
(a) the note filter (if any) is switched out of circuit;
(b) a signal of type A2 modulated to a depth of 30 per centum with a
frequency of 400 cycles per second is injected at the standard input level;
and
(c) the receiver gain is manually adjusted to give the standard output
level.
(3) For the purposes of this item, spurious whistles shall be regarded as
noise.
Blocking
10. The change in output of the receiver shall not exceed 3 decibels-
(a) at any frequency within the range of frequencies specified in item 4
of
this Schedule; and
(b) at all levels of a wanted signal up to 50 decibels above the standard
input level, whether of type A1 or type A2, when locally generated signals of
type A1 or type A2 at a level of 40 decibels above the level of the wanted
signal and spaced 10 kilocycles per second from the carrier of the wanted
signal are applied.
Intermodulation
11. The input level of each of two unwanted signals shall not be less than
plus 75 decibels relative to the standard input level when-
(a) the receiver is adjusted to give standard output level with a locally
generated wanted signal of standard input level modulated to a depth of 30
per
centum with a note frequency of 400 cycles per second at any frequency within
the range of frequencies specified in item 4 of this Schedule;
(b) the input wanted signal has been removed; and
(c) two unwanted locally generated signals-
(i) each of which is of a frequency not less than 50 kilocycles per
second from the frequency of the wanted signal;
(ii) the frequency sum or frequency difference of which is equal to the
frequency of the wanted signal; and
(iii) one of which is modulated to a depth of 30 per centum with a note
frequency of 400 cycles per second and the other is unmodulated,
are applied simultaneously at equal input levels so as to give an output
equal to that previously obtained with the wanted signal.
Radiation
12. The direction-finder shall not in normal service produce a field
exceeding 0.1 microvolt per metre when measured at a distance of 1 mile from
the receiver.
13. The direction-finder shall be deemed to comply with the last preceding
item if, when-
(a) the receiver, with the goniometer (if any) but without the aerial
system, is placed centrally in a screened earthed enclosure at least 6 feet
cube;
(b) the earth terminal is connected to the inside of the screen;
(c) each aerial terminal in turn is connected through an unscreened 4-turn
rectangular search coil, 1 foot square, situated within the enclosure and an
unscreened lead to a resistive measuring instrument mounted outside the
enclosure and having its other terminal earthed;
(d) the aerial terminal or terminals of the receiver, other than the
terminal connected to the measuring instrument, are earthed one at a time or
in any
combination or remain unearthed or are interconnected in any combination; and
(e) the receiver is energized and unscreened headphones are connected to
it,
the power measured by the measuring instrument, when connected in the manner
specified in paragraph (c) of this item, does not exceed 4 x 10-^10^ watt
whatever the resistance of the measuring instrument or the adjustment of the
receiver and notwithstanding that the search coil is short-circuited or moved
in any way other than a way that causes it to approach within 6 inches of the
receiver case.
Tuning Drift and Stability
14. After the receiver has been switched on for 5 minutes and tuned to any
frequency within the frequency range specified in item 4 of this Schedule the
tune frequency shall not change by more than 1 part in 1,000 in any period of
5
minutes.
15. A change of 5 per centum in any one of the supply voltages to the
receiver, or to a power unit associated with the supply voltages, shall not
cause the tune frequency to change by more than 3 parts in 10,000.
16. A change of ambient temperature of 5 degrees Centigrade within the range
0 degrees Centigrade to 50 degrees Centigrade applied after the receiver has
been
switched on for 1 hour shall not cause the tune frequency to change by more
than 1 part in 1,000.
Heterodyne Note Stability
17. The heterodyne note stability of the receiver shall be such that-
(a) the frequency of a heterodyne note which is initially 1 kilocycle per
second shall not vary by more than 100 cycles per second when an input signal
is increased over a range of levels from 0 to 60 decibels above the standard
input; and
(b) at all input levels within the range specified in the last preceding
paragraph, a beat note of 200 cycles per second can be obtained by tuning
either towards or away from zero beat.
Fidelity
18. The maximum change in level of the output of the receiver shall be less
than 8 decibels when-
(a) the modulation frequency of an input signal of constant level and
modulation depth, applied at a level in the range from the standard input
level
to 50 decibels above the standard input level, is varied continuously from
300
cycles per second to 1,500 cycles per second; and
(b) the output of the receiver does not exceed the standard output level.
Accuracy of Bearings
19. The bearings indicated by the scale of the direction-finder shall, at
all
frequencies in the range of frequencies specified in item 4 of this Schedule,
throughout the whole 360 degrees of azimuth and after due allowance has been
made for site errors, be correct within plus or minus 1 degree of the true
bearing when the direction-finder is tested using waves of type A2 modulated
to
a depth of from 80 per centum to 100 per centum and with a vertically
polarized
field having a level of 40 decibels relative to 1 microvolt per metre.
Quality of Minima
20. Changes in the setting of the bearing indicator of the direction-finder
5
degrees and 90 degrees in either direction from the position or positions of
minimum output shall, at all frequencies in the range of frequencies
specified
in item 4 of this Schedule, cause the audio-frequency output to increase by
not
less than 18 decibels and not less than 35 decibels, respectively, when the
direction-finder is arranged for the taking of bearings and is tested under
the
conditions specified in the last preceding item, but with a field strength
sufficient to give a signal/noise ratio of not less than 50 decibels with the
loop aerial system adjusted for maximum output.
Efficiency of Sense-Finder
21. The audio-frequency output level of the receiver due to the wanted
signal
shall, when-
(a) the direction-finder is adjusted for the determination of sense, and
is
tested under the conditions specified in item 19 of this Schedule, but with a
field strength sufficient to give a signal/noise ratio of not less than 50
decibels with the loop aerial system adjusted for maximum output; and
(b) the sense indicator is adjusted to indicate any bearing within plus or
minus 10 degrees of the true bearing,
be not less than 20 decibels below the output level that is obtained when the
sense indicator is adjusted to indicate a bearing within 180 degrees plus or
minus 10 degrees of the true bearing.
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