I, RALPH WILLIS, the Minister for Transport and Communications, hereby make the following standard under Section 9 of the Radiocommunications Act 1983.
Dated 21st December 1989.
RALPH WILLIS
Minister for Transport and Communications
____________
STANDARD FOR 406 MHz SATELLITE DISTRESS BEACONS
PART 1—PRELIMINARY
Citation
This standard may be cited as “Ministerial Standard 309”.
Interpretation
In this standard, unless the contrary intention appears—
‘dBuV/m’ means decibel relative to one microvolt per metre;
‘device’ means a device to which this standard applies;
‘Hz’ means hertz;
‘kHz’ means kilohertz;
‘MHz’ means megahertz;
‘MS’ means Ministerial Standard;
‘radiation’ means the outward flow of energy from any source by means of radio transmission;
‘satellite distress beacon’ means a satellite emergency position indicating radio beacon, satellite emergency locator transmitter or satellite personal locator beacon;
‘satellite emergency position indicating radio beacon’ means a device, designed or intended for use in the Maritime Mobile-Satellite Service, which incorporates a transmitter the emissions of which are intended to facilitate search and rescue operations;
‘satellite emergency locator transmitter’ means a device, designed or intended for use in the Aeronautical Mobile-Satellite Service, which incorporates a transmitter the emissions of which are intended to facilitate search and rescue operations;
‘satellite personal locator beacon’ means a device, designed or intended for use in the Land Mobile-Satellite Service, which incorporates a transmitter the emissions of which are intended to facilitate search and rescue operations;
‘Specification’ means the document known as “Specification for COSPAS-SARSAT 406 MHz Distress Beacons C/S T.001 Issue 2—Revision 0” dated November 1988;
‘standard device’ means a device which complies with this standard;
‘transmitter’ means a radiocommunications transmitter as defined in the Radiocommunications Act 1983; and
‘°C’ means degrees Celsius.
Devices to which this standard applies
3. This standard applies to all satellite distress beacons designed or intended for use on the carrier frequency 406.025 MHz, except for satellite emergency locator transmitters.
PART 2—GENERAL
Equipment markings
4. (1) Subject to sub-clause 4 (3), there shall be displayed on a device—
(a) a compliance statement in the form set out in Schedule 1—
(i) indicating that the device complies with this standard; and
(ii) citing the type approval number shown on the compliance statement certificate issued in respect of the device under section 12 of the Radiocommunciations Act 1983;
(b) the name of its manufacturer;
(c) the name of the country of its manufacture;
(d) its type or model designation which shall be distinctively different from that of imported equipment requiring modification before it complies with this standard;
(e) its equipment serial number in decimal format; and
(f) simple operating instructions including the warning: “Not to be operated except in an emergency—improper use carries a severe penalty”.
(2) A statement or marking displayed on a device in accordance with sub-clause 4 (1) shall be clearly visible on the exterior surface of the device, indelible, durable, tamper proof and affixed in such a manner as not to be removable except by destruction or defacing.
(3) The requirement of paragraph 4 (1) (a) does not apply to a device unless the importer, manufacturer or supplier of the device, as the case may be, has been issued with a compliance statement certificate in respect of the device.
Adjustment mechanisms
(1) For the purpose of this clause an ‘adjustment mechanism’ is a mechanism which enables the operation of a standard device to be altered so that the device no longer complies with this standard.
(2) Any adjustment mechanism shall be contained within the housing of a device and shall be accessible only with the use of tools such as screwdrivers and spanners.
PART 3—TRANSMITTER OPERATION ON 406.025 MHz
Adoption of matter contained in the Specification
This standard adopts all of the requirements contained in the document “Specification for COSPAS-SARSAT 406 MHz Distress Beacons C/S T.001 Issue 2—Revision 0” dated November 1988 (“the Specification”) which is set out in Schedule 2, insofar as it relates to satellite personal locator beacons and to satellite emergency position indicating radio beacons.
Application and Amendments
(1) A device which is a satellite personal locator beacon shall comply with the provisions of the Specification.
(2) Subject to sub-clauses 7 (3) and 7 (4), a device which is a satellite emergency position indicating radio beacon shall comply with the provisions of the Specification.
(3) In the case of a device which is a satellite emergency position indicating radio beacon the matter adopted by this standard is amended by substituting “48 hours” for “24 hours” wherever it occurs in compliance with International Maritime Organisation requirements.
(4) In addition to the requirements of sub-clauses 7 (2) and 7 (3) a device which is a satellite emergency position indicating radio beacon shall incorporate, as an integral part of the device, a homing transmitter operating on the nominal carrier frequency 121.5 MHz and complying with the requirements of Part 4 of this standard.
NOTES 1 As indicated by clause 3, this standard does not apply to satellite emergency locator transmitters and therefore the requirements set out in the Specification have not been adopted in respect of those devices.
2 For the purpose of this Ministerial Standard no additional environmental or operational requirements as referred to in sections 4.3 and 4.4 and 4.5.2 of the Specification are required.
PART 4—HOMING TRANSMITTER
Interpretation
In this part ‘homing transmitter’ means an auxiliary homing transmitter of a device which is a satellite emergency position indicating radio beacon.
Conditions of Operation
The requirements of this part shall be met by a homing transmitter when it operates:
(1) at an ambient temperature of between -20°C and 55°C inclusive; and
(2) continuously for a minimum period of 48 hours.
Nominal carrier frequency
Subject to clause 11, a homing transmitter shall only be capable of operating on the carrier frequency 121.5 MHz.
Frequency error
The carrier frequency error of a homing transmitter shall not exceed ±3 kHz.
Radiated signal field strength
The peak field strength of the radiated signal from a homing transmitter shall not be less than 99 dBuV/m when measured in the vertical plane at a distance of 10 metres from the antenna at a height of 1.75 metres above the level of water in which the device is floating.
Type of emission
The emission from a homing transmitter shall comprise a double sideband, full carrier signal, amplitude modulated to a depth of not less than 85%.
Modulation characteristic
(1) Modulation of a homing transmitter shall consist of an audio frequency signal swept upwards through at least 700 Hz within the range 300 Hz to 1600 Hz with a repetition rate of between 2 Hz and 4 Hz; and
(2) The delay between consecutive sweeps shall not exceed one-tenth of the up-sweep time.
Emission spectrum
15. An emission from a homing transmitter shall include a clearly defined carrier frequency component distinct from the modulation sideband components. At least 30% of the power emitted shall be contained during any modulation cycle within ± 30 Hz of the actual carrier frequency.
Transmitter duty cycle
(1) Following activation a homing transmitter may operate either continuously (100% duty cycle) or intermittently. In the case of intermittent operation the following conditions shall apply:
(a) repetition period of 30 seconds ± 10%; and
(b) duty cycle within the range 40% to 60% inclusive.
(2) A transmission from a homing transmitter may be interrupted during the 406.025 MHz message transmissions.
Spurious radiation
The peak field strength of each spurious radiation from a homing transmitter shall not exceed 75 dBuV/m when measured at a distance of 10 metres from the antenna.
Antenna characteristics
The radiation characteristics of a homing transmitter shall be such that when the device is floating in water the radiation is:
(1) vertically polarised;
(2) omnidirectional in the horizontal plane; and
(3) predominant at low angles of elevation.
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SCHEDULE 1 Clause 4
THE FORM OF A COMPLIANCE STATEMENT
“COMPLIES WITH MS309
TYPE APPROVAL NO……”
_______________
SCHEDULE 2 Clause 6
THE “SPECIFICATION FOR COSPAS-SARSAT
406 MHz DISTRESS BEACONS C/S T.001
ISSUE 2—REVISION 0” REPRODUCED WITH THE PERMISSION OF COSPAS-SARSAT.
SPECIFICATION FOR
COSPAS-SARSAT
406 MHz DISTRESS BEACONS
C/ST.001
ISSUE 2 - REVISION 0
NOVEMBER 1988
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SPECIFICATION FOR COSPAS-SARSAT 406 MHz DISTRESS BEACONS
History
Issue
Revision
Date
Comments
1
0
April 1986
Original issue approval by CSSC
2
0
(Nov 1987)
Draft 1 - revisions agreed to at the CSSC-3 meeting
2
0
(Jan 1988)
Draft 2 - revisions agreed to at CSSC-4
2
0
(13 May 1988)
Draft 3 - in new format, plus minor revisions to harmonize with CCIRRecommendation 633 and other minor editorial changes
2
0
(July 1988)
Draft 4 - revisions agreed to at TWG 88-1 meeting (self-test mode and additional requirement on long message beacons).
B3.2.2.2 Stability During Transmission, Rise and Fall Times
B-7
B3.2.2.3 Equivalent Isotropic Radiated Power
B-7
B3.2.2.4 Spurious Output
B-7
B3.2.3 Data Encoding and Modulation
B-7
B3.3 Voltage Standing-Wave Ratio
B-7
B3.4 Protection Against Continuous Transmission
B-7
- v -
TABLE OF CONTENTS (Continued)
LIST OF FIGURES:
Figure 2.1:
Short Message Format
Figure 2.2:
Long-Message Format
Figure 2.3:
Spurious Emission Mask for 406.0 to 406.1 MHz Band
Figure 2.4:
Data Encoding
Figure 2.5:
Definition of Modulation Rise and Fall Times
Figure 2.6:
Definition of Modulation Symmetry
Figure 4.1:
Temperature Gradient
Figure A1:
General 406 MHz Message Format
Figure A2:
Unique Data in the 406 MHz Message for the Maritime/Location Protocol
Figure A3:
Unique Data in the 406 MHz Message for the 8 Possible User Protocols
Figure A4:
Bit Assignment for the 61 Bits in the Protected Data Field of the 9 Available Protocols
Figure A5:
Summary of Coding Options for 406 MHz Beacons
Figure B1:
Example of a 406 MHz Beacon Test Bench
Figure B2:
Definition of Measurement Intervals
Figure B3:
Transmission Timing
Figure B4:
Medium-Term Frequency Stability Measurement
LIST OF TABLES:
Table A1:
Modified Baudot Code
Table A2:
IMO Maritime Emergency Codes
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1.0 - INTRODUCTION
1.1 Purpose
The purpose of this document is to define the minimum requirements to be used for the development and manufacture of 406 MHz Emergency Locator Transmitters (ELTs), Emergency Position-Indicating Radio Beacons (EPIRBs), and Personal Locator Beacons (PLBs). In this document, the term ELT indicates an aviation distress beacon, an EPIRB a maritime distress beacon and a PLB a distress beacon for use in the land mobile-satellite service.
Specifications which are critical to the COSPAS-SARSAT System are defined in detail; specifications which could be developed by the national authorities are identified in more general terms.
1.2 Scope
This document contains the minimum requirements that apply to COSPAS-SARSAT distress beacons. It is divided into the following sections:
a) Section 1 is the introduction.
b) Section 2 gives the system requirements applicable to all types of beacons. When met, these requirements will enable the beacons to provide the intended service in terms of location probability and accuracy and will not disturb the system operation.
c) Section 3 deals with the message content. Basic message structure is defined. Assignment and meaning of the available data bits are defined in Annex A to this specification.
d) Section 4 defines a set of environmental and operational requirements. These requirements are not meant to be exhaustive and may be complemented or replaced by more detailed national or international standards (e.g. RTCA standards for ELTs). However, they represent the minimum environmental and operational performance for a COSPAS-SARSAT beacon to be compatible with the the COSPAS-SARSAT System.
e) Annex A defines the beacon coding.
f) Annex B describes the measurement methods that can be used for the COSPAS-SARSAT type certification of the beacons. They are not necessarily the only methods for measuring specific parameters. Alternative measuring techniques can be approved by COSPAS-SARSAT. Again, they are not meant to be exhaustive, except for the part related to the system requirements defined in Section 2 of this document (e.g. frequency, transmitted power, etc.). The other beacon performance parameters may be complemented or replaced by national or international standards.
END OF THIS SECTION
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2.0 - SYSTEM REQUIREMENTS
2.1 Beacon Functional Elements
This section defines the requirements for the two following functional elements of a 406 MHz distress beacon.
a) Digital message generator
b) Modulator and 406.025 MHz transmitter
2.2 Digital Message Generator
The digital message generator will key the modulator and transmitter so that the message defined in Section 3 is transmitted.
2.2.1 Repetition Period
The period between transmissions shall be 50 s ±5 percent. The repetition period shall not be so stable that any two transmitters appear to be synchronized closer than a few seconds over a 5-minute period. The intent is to randomize the period between transmission bursts such that no two beacons will have all of their bursts coincident.
An acceptable alternative for a production run of any type or model of beacon would be an equal distribution of fixed repetition periods of 8 of more values approximately equally spaced over the range of 47.5 to 52.5 seconds.
2.2.2 Total Transmission Time
The total transmission time shall be 440 ms ±1 percent for the standard short message and 520 ms ±1 percent for the optional long message.
2.2.3 CW Preamble
The initial 160 ms ±1 percent of the transmitted signal shall consist of an unmodulated carrier at the transmitter frequency measured at the 90 per cent power point.
2.2.4 Digital Message
a. Short Message
The final 280 ms ±1 percent of the transmitted signal shall contain a 112-bit message at a bit rate of 400 bps ±1 percent;
b. Long Message
The final 360 ms ±1 percent of the transmitted signal shall contain a 144-bit message at a bit rate of 400 bps ±1 percent.
2.2.4.1 Bit Synchronization
A bit-synchronization pattern consisting of “1’s” shall occupy the first 15-bit positions.
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2.2.4.2 Frame Synchronization
A frame (or message) synchronization pattern consisting of 9 bits shall occupy bit positions 16 through 24. The normal frame synchronization pattern shall be 000101111. However, if the beacon radiates a modulated signal in the self-test mode, the frame synchronization pattern shall be 011010000. (i.e. the last 8 bits are complemented)
2.2.4.3 Format Flag
Bit 25 is a flag bit used to indicate the length of the message to follow. Value “0” indicates a short message; value “1” indicates a long message.
2.2.4.4 Message Content
The content of the remaining 87 bits (short message - see Figure 2.1) and 119 bits (long message - see Figure 2.2) is defined in Section 3.
2.3 Modulator and 406 MHz Transmitter
2.3.1 Transmitted Frequency
The transmitted frequency shall initially be set at 406.025 MHz ± 2 kHz. The transmitted frequency shall not vary more than ± 5 kHz in 5 years including the initial offset. It shall not vary more than 2 parts in 109 in 100 ms (see Annex B for method of measurement).
The transmitted medium-term frequency stability shall be defined by the mean slope of the frequency versus time over a 15-minute period and by the residual frequency variation about the mean slope. The mean slope shall not exceed 1 part in 109 per minute. Residual frequency variation shall not exceed 3 parts in 109 (see Note 1).
This performance shall be met for all defined environmental conditions, including the temperature gradient defined in Section 4.2.2, after a maximum warm-up period of 15 minutes.
The mean slope and the residual frequency variation shall be measured as follows: data shall be obtained by making 18 sequential frequency measurements, one every repetition period (50 sec ±5%, see section 2.2.1); each measurement shall be a 100 ms frequency average performed during the modulated part of the message.
The mean slope is defined as that of the least-squares straight-line fit to the 18 data points. Residual frequency variation is defined as the rms (root mean square) error of the points relative to the least-squares estimate.
______________
Note 1: For an interim period the following relaxation in frequency stability is permitted for beacons manufactured by 1 January, 1991: mean slope 2 parts in 109 per minute and residual frequency variation 5 parts in 109. Since this relaxation will result in some deterioration in system performance, manufacturers are encouraged to meet the full specification as soon as possible.
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Figure 2.1: Short Message Format
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Figure 2.2: Long Message Format
Notes: (1) Bit Synchronization: 15 “1” bits
(2) Frame Synchronization: 000101111 (except as in sec. 4.5.4)
(3) “0” bit indicates short-message format
“1” bit indicates long-message format
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2.3.2 Transmitter Power Output
The transmitter power output shall be within the limits of 5 W ± 2 dB measured into a 50 ohm load with a voltage standing-wave ratio (VSWR) not greater than 1.25:1. This power output shall be maintained during 24-hour operation at the minimum specified temperature. Power output rise time shall be less than 5 ms measured between the 10% and 90% power points.
2.3.3 Antenna Characteristics
The following antenna characteristics are defined for elevation angles greater than 5° and less than 60°.
- Pattern: hemispherical
- Polarization: circular (RHCP) or linear
- Gain: between -3 dBi and 4 dBi over 90% of the above region
- Gain variation (azimuth): less than 3 dB
- Antenna VSWR: not greater than 1.5:1
The antenna characteristics should be measured in a configuration as close as possible to its operational condition.
2.3.4 Spurious Emissions
The in-band spurious emissions shall not exceed the levels specified by the signal mask in Figure 2.3.
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Figure 2.3: Spurious Emission Mask for 406.0 to 406.1 MHz Band
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2.3.5 Data Encoding
The data shall be encoded biphase L. (See Figure 2.4).
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Figure 2.4: Data Encoding
2.3.6 Modulation
The carrier shall be phase modulated plus and minus 1.1 ± 0.1 radians peak, referenced to an unmodulated carrier. Modulation sense shall be as shown in Figure 2.4.
The rise (ΊR) and fall (ΊF) times of the modulated waveform shall be 150 ± 100μs between the 0.9 points of the peak-to-peak phase transition as shown in Figure 2.5.
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Figure 2.5: Definition of Modulation Rise and Fall Times
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Modulation symmetry (see Figure 2.6) shall be such that:
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Figure 2.6: Definition of Modulation Symmetry
2.3.7 Voltage Standing-Wave Ratio
The modulator and 406 MHz transmitter shall be able to meet all requirements, except for those in paragraph 2.3.2 (power output), at any VSWR between 1:1 and 3:1, and shall not be damaged by any load from open circuit to short circuit.
2.3.8 Maximum Continuous Transmission
The 406 MHz distress beacon shall be designed to limit any inadvertent continuous transmission to a maximum of 45 seconds.
END OF THIS SECTION
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3.0 - MESSAGE CONTENT
3.1 Basic Structure
The digital message which is transmitted by the 406 MHz beacon consists of:
a) 112 bits for the short message,
b) 144 bits for the long message.
These bits are divided into four groups:
(1) The first 24 bits transmitted, positions 1 through 24, are system bits; they are defined in Section 2 and are used for the bit and frame synchronization of the on-board processor.
(2) The following 61 bits, positions 25 through 85, are data bits. The first data bit (position 25) indicates if the message is short or long: “0” short message, “1” long message.
(3) The following 21 bits, positions 86 through 106, are a Bose-Chaudhuri-Hocquenhem or BCH (82,61) error-correcting code. This code is a shortened form of a BCH (127,106) triple error-correcting code obtained from the following generator polynomial:
g5(x) = g3(x) • (7,4,3,2,0)
g3(x) = g1(x) • (7,3,2,1,0)
g1(x) = (7,3,0)
Since the message sent will be only 61 bits (i.e. less than the 106 bits), it is assumed that the unnecessary bits will be set to zero for computation of the error-correction bits. These zero message bits will be thought to be at the beginning of the message and will not be transmitted since they are always zero and contribute no new information.
(4) (a) Short message: The last 6 bits of the message in positions 107 through 112 are data bits.
(b) Long message: The last 38 bits of the message in positions 107 through 144 are data bits.
3.2 Beacon Coding
Beacon coding is defined in Annex A to this specification.
END OF THIS SECTION
4 - 1
4.0 - ENVIRONMENTAL AND OPERATIONAL REQUIREMENTS
4.1 General
As explained in Section 1.2, the environmental and operational requirements defined in this section are not intended to be exhaustive. They are minimum requirements which may be complemented by national or international standards.
4.2 Thermal Environment
4.2.1 Temperature Range
Two standard classes of temperature range are defined inside which the system requirements of Section 2 shall be met:
Class 1:
-40°C to +55°C
Class 2:
-20°C to +55°C
The temperature range shall be permanently marked on the beacon.
4.2.2 Temperature Gradient
All system requirements of Section 2, including the frequency requirements defined in Section 2.3.1, shall be met when the fully packaged beacon is subjected to the temperature gradient shown in Figure 4.1.
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NOTES: Tmin = -40°C (Class 1 beacon)
Tmin = -20°C (Class 2 beacon)
ton = beacon turn on after 2 hour “cold soak”
tmeas = start time of frequency stability measurement (ton + 15min)
Figure 4.1: Temperature Gradient
4.2.3 Thermal Shock
All system requirements of Section 2 shall be met for measurements beginning 15 minutes after simultaneously activating the beacon and applying a thermal shock of 30°C within the specified operating temperature range of the beacon. Subsequently, system requirements shall continue to be met for a minimum period of two (2) hours.
4-2
4.3 Mechanical Environment
Beacons shall be submitted to vibration and shock tests consistent with their intended use.
Internationally-recognized standards such as RTCA/DO-183 for ELTs could be used by the national authorities.
4.4 Other Environmental Requirements
Other environmental requirements such as humidity tests, altitude tests, over/under pressure tests, waterproofness tests, sand and dust tests, fluids susceptibility tests, etc., may be defined by national authorities, preferably using internationally-recognized standards.
4.5 Operational Requirements
4.5.1 Duration of Continuous Operation
The minimum duration of continuous operation shall be at least 24 hours* at minimum temperature. This characteristic shall be permanently marked on the beacon.
4.5.2 Other Operational Requirements
Other operational requirements such as installation and maintenance methods, remote monitoring, activation methods on planes or boats, etc. may be defined by national authorities.
4.5.3 Auxiliary Radio-Locating Device
The distress beacon may incorporate an auxiliary radio-locating device at another frequency (121.5 MHz, 9 GHz SART, etc.) which is compatible with existing radio-locating equipment.
Any such auxiliary radio-locating device must satisfy all the national performance standards applicable to radio-locating devices at the selected auxiliary frequency.
4.5.4 Beacon Self-Test Mode
It is desirable that no RF energy be radiated in any self-test mode used as a routine exercise to verify beacon operation. However, if this is not possible, then the RF test transmission must be limited to one burst of 440 ms maximum. If modulated, the signal must have a frame synchronization pattern of 011010000. This bit pattern complements the last 8 bits of the normal frame synchronization pattern so that this test burst will not be processed by the satellite equipment.
* For installations meeting IMO GMDSS requirements, a minimum operating lifetime of 48 hours is necessary.
END OF THIS SECTION
A - 1
ANNEX A - BEACON CODING OPERATION
A1.0 - GENERAL
This Annex defines the 406 MHz beacon digital message coding. The digital message shown in Figure A1 is divided into the following six bit fields:
Bit Field Name
Bit Field Location
1. Bit synchronization2. Frame synchronization3. Protected field4. Error-correcting code5. National use/emergency code6. Long message (optional)
bit 1 through bit 15bit 16 through bit 24bit 25 through bit 85bit 86 through bit 106bit 107 through bit 112bit 113 through bit 144
The bit synchronization and frame synchronization fields are defined in Sections 2.2.4.1 and 2.2.4.2, respectively.
The error-correcting code is defined in Section 3.1.
The protected field, the national use/emergency code, and the long message field are shown in Figures A2 and A3 and are defined in this Annex. Figure A4 shows the protected field for the nine available protocols, and Figure A5 summarizes all the coding options for the entire message.
A2.0 - PROTECTED FIELD
The protected field consists of 61 bits (i.e. bit 25 through bit 85). The first bit (i.e. bit 25) is a format flag which shows whether the message is short or long using the following code:
0 - short format
1 - long format
The identification (ID) field, which begins at bit 26 after the format flag and ends at bit 85, has the following structure:
Bits
Usage
2627-3637-85
protocol flagcountry codedata field
A2.1 Protocol Flag
Bit 26 in the ID field is used to identify whether the Maritime/Location Protocol (bit 26 - 0) or one of the eight possible User Protocols (bit 26-1) shown in Figure A4 is used.
A - 2
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A - 3
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Notes: (1) “0” For short message and “1” for long message format
(2) Sot to “0” for this format
(3) Binary equivalent of the appropriate three digit decimal number (MSB on left). See para A2.2
(41 Latitude and longitude of beacon in degrees and minutes
(3) “1” for emergency code use
(6) “0” for manual activation only and “1” for automatic and manual activation typo of beacon
(7) Four user-settable bits for emergency codes in Table A.2
(8) Optional data giving time, course, and speed of vassal
Figure A2: Unique Data in the 406 MHz Message for the Maritime/Location Protocol
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Notes: (1) “0” For short message and “1” for long message format
(2) Sot to “1” for this format
(3) Binary equivalent of the appropriate three digit decimal number (MSB on left). See para A2.2
(4) Specifies orbitography, aviation, maritime, serialized, test or radio call-sign format (plus two spare formats)
(5) Specifies which auxiliary radio-locating device is incorporated in the beacon
(6) “0” for national use or undesignated and “1” for emergency code
(7) “0” for manual activation only and “1” for automatic and manual activation type of beacon
(8) Four user-settable bits for national use or for emergency codes as in Table A.2
(9) Optional data giving latitude and longitude of beacon in degrees and minutes
Figure A3: Unique Data in the 406 MHz Message for the 8 Possible User Protocols
A - 4
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Figure A4: Bit Assignment for the 61 Bits in the Protected Data Field of the 9 Available Protocols
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Figure A5: Summary of Coding Options for 406 MHz Beacons
A - 6
A2.2 Country Code
Bits 27-36 in the ID field designate a three-digit decimal country code number expressed in binary notation. Country codes are based on the International Telecommunications Union (ITU) Maritime Identification Digit (MID) country codes shown in Table 1 of Appendix 43 of the ITU Radio Regulations. National administrations allocated more than one MID code may opt to use for themselves only one of these codes. The country code will be addressed further under the discussion of each protocol.
A2.3 Maritime/Location Protocol
The maritime/location protocol has the following structure:
Bits
Usage
26
protocol flag (-0)
27-36
country code (MID)
37-56
trailing 6 digits of ship station identity (20-bit MID number)
57-85
29 bit location
The country code for the maritime/location protocol is that of the country of vessel registration.
Bits 37-56 designate 6-decimal numeric characters expressed in binary notation that are based on the ITU maritime mobile service identities (ITU Radio Regulations, Appendix 43, Section 3 - Ship Station Identities).
Bits 57-85 designate the following using binary notation:
Bits
Usage
57-63
degrees latitude
64-69
minutes latitude
70
0-north; l-south
71-78
degrees longitude
79-84
minutes longitude
85
0-east; l-west
A2.4 User Protocols
The user protocols have the following structure:
Bits
Usage
26
protocol flag (-1)
27-36
country code (MID)
37-39
user protocol type
40-83
data field
84-85
auxiliary radio-locating device(s)
A - 7
Bits 37-39 in the protocol-type field designate one of eight user protocols and are expressed as one octal character. This determines how the remaining bits in the data field are encoded/decoded. The eight user protocols are as follows:
binary number
octal character
user protocol type
000
0
orbitography
001
1
aviation
010
2
maritime
011
3
serialized
100
4
spare
101
5
spare
110
6
radio call sign
111
7
test
Bits 40-83 are used to encode the actual identification of the beacon and shall be unique for each beacon. They will be discussed separately for each user protocol.
Bits 84-85 are used to indicate the type of auxiliary radio-locating device(s) forming part of the particular beacon for each user protocol (excluding orbitography beacons). The assignment of bits is as follows:
It is desirable that administrations using the “other auxiliary radio-locating device(s)” category (i.e. 11) advise the COSPAS-SARSAT Secretariat and the appropriate SAR authorities which auxiliary radio-locating device(s) and its (their) signal characteristics they are using. If other auxiliary radio-locating device(s) is (are) used in addition to 121.5 MHz, the code for 121.5 MHz should be used.
A2.4.1 Orbitography Protocol
The orbitography protocol has the following structure:
Bits
Usage
26
protocol flag (-1)
27-36
country code (MID)
37-39
user protocol type (-000)
40-85
data field
Bits 27-36 designate the country in which the beacon is registered.
Bits 40-85 are defined by the Technical Working Group of the COSPAS-SARSAT Council (CSC).
A - 8
A2.4.2 Aviation Protocol
The aviation protocol has the following structure:
Bits
Usage
26
protocol flag (-1)
27-36
country code (MID)
37-39
user protocol type (-001)
40-81
aircraft tail number
82-83
spare (-00)
84-85
auxiliary radio-locating device
Bits 27-36 designate the country in which the aircraft is registered. However, it may also indicate the country to which an aircraft has been leased if the national authority in the leasing country requires this information within the country code.
Bits 40-81 designate the aircraft tail number (i.e. registration number) which is encoded using the modified Baudot code shown in Table A1. This code enables 7 characters (6×7-42) to be encoded using 42 bits. This data will be right justified with a Baudot space (100100) being used where no character exists.
A2.4.3 Maritime Protocol
The maritime protocol has the following structure:
Bits
Usage
26
protocol flag (-1)
27-36
country code (MID)
37-39
user protocol type (-010)
40-75
radio call sign or trailing 6 digits of ship station identity
76-81
specific beacon
82-83
spare (-00)
84-85
auxiliary radio-locating device
Bits 27-36 designate the country of vessel registration.
Bits 40-75 designate the radio call sign or the last 6 digits of the 9 digit ship station identity using the modified Baudot code shown in Table A1. This code enables 6 characters (6×6 - 36) to be encoded using 36 bits. This data will be right Justified with a Baudot space, (100100) being used where no character exists.
Bits 76-81 (coded in modified Baudot) differentiate between beacons carried by the same vessel. A Baudot zero (001101) shall be used for the only or the primary beacon. Other characters may be used for survival craft or other beacons.
This protocol and the radio call sign user protocol may be used for beacons that require coding with a radio call sign. This protocol should be used for radio call signs of 6 or less characters and where the 5th or 6th characters are letters. For radio call signs where letters are used only within the first four characters, the radio call sign user protocol should be used.
A - 9
Table A1: Modified Baudot Code
Letter
Code
Figure
Code
A
111000
(-)**
011000
B
110011
C
101110
D
110010
E
110000
3
010000
F
110110
G
101011
H
100101
I
101100
8
001100
J
111010
K
111110
L
101001
M
100111
N
100110
O
100011
9
000011
P
101101
0
001101
Q
111101
1
011101
R
101010
4
001010
S
110100
T
100001
5
000001
U
111100
7
011100
V
101111
W
111001
2
011001
X
110111
/
010111
Y
110101
6
010101
Z
110001
( )*
100100
* Space
** Hyphen
A - 10
A2.4.4 Serialized Protocol
The serialized protocol will permit the manufacturing of beacons whose ID will not change once entered. Units will be identified in a data base giving specifics about the unit.
The serialized protocol has the following structure:
Bits
Usage
26
protocol flag (-1)
27-36
country code (MID)
37-39
user protocol type (-011)
40-43
beacon type
44-63
serial number
64-83
national use
84-85
auxiliary radio-locating device
Bits 27-36 designate the country of beacon registration.
Bits 40-43 will indicate the beacon type as follows:
0000 - aviation (i.e. ELT)
0100 - maritime (i.e. float-free EPIRB)
1000 - survival (i.e. non float-free EPIRB)
1100 - personal locator beacon (PLB)
Bits 44-63 will be a serialized ID code from 0 to 1,048,575 (i.e. 220-1) expressed in binary notation. Bits 64-83 are for national use and control but will be made public when assigned.
A2.4.5 Radio Call-Sign Protocol
The radio call-sign protocol is established to accommodate a seven-character radio call sign where letters may be used in the first four characters.
The radio call-sign protocol has the following structure:
Bits
Usage
26
protocol flag (-1)
27-36
country code (MID)
37-39
user protocol type (-110)
40-75
radio call sign
76-81
specific beacon
82-83
spare (-00)
84-85
auxiliary radio-locating device
Bits 27-36 designate the country of aircraft or vessel registration.
A - 11
Bits 40-75 contain the radio call sign of up to seven characters. Shorter call signs are left justified in the field and padded with ‘space’ characters. Bits 40-63 designate the first four characters, and are encoded in modified-Baudot code in accordance with Table A1. Bits 64-75 designate the last three characters of the call sign and are encoded in binary-coded-decimal (BCD) notation. The bit pattern ‘1010’ is used as the ‘space’ character in BCD notation.
Bits 76-81 (coded in modified Baudot) differentiate between beacons carried by the same vessel or aircraft. A Baudot zero, i.e. 001101, shall be used for the only or the primary beacon. Other characters may be used for survival craft or other beacons.
A2.4.6 Test Protocol
The test protocol will be used for demonstrations, national tests, training exercises, etc., Mission Control Centres (MCCs) will not forward these locations unless requested by the nation conducting the test.
The test protocol has the following structure:
Bits
Usage
26
protocol flag (-1)
27-36
country code (MID)
37-39
user protocol type (-111)
40-83
national use
84-85
auxiliary radio-locating device
Bits 27-36 designate the country of beacon registration.
Bits 40-83 are for national use.
A3.0 - NATIONAL USE/EMERGENCY CODE
The national use/emergency code field consists of bits 107 to 112.
Bit 107 is a flag bit to indicate whether bits 109 to 112 are for national use (0) or for the emergency code (1).
Bit 108 indicates if the beacon is the type that can be activated manually only (0) or that can be activated both manually and automatically (1).
When bits 109 to 112 are for national use, it is desirable that administrations so advise the COSPAS-SARSAT Secretariat and the appropriate SAR authorities.
When the emergency code is used (i.e. bit 107 - 1), bits 109 to 112 are coded with the International Maritime Organization (IMO) maritime emergency codes (Table A2) for all maritime distresses (i.e. maritime/ location protocol, maritime user protocol, serialized user maritime and survival protocols, and radio call-sign protocol), or with the following codes for all other users (i.e. orbitography, aviation, and serialized user aviation and personal protocols):
A - 12
bit 109 - fire (1) or no fire (0)
bit 110 - medical help (1) or no medical help required (0)
bit 111 - disabled (1) or not disabled (0)
bit 112 - spare (0)
When neither the national use nor the emergency code are implemented, bit 107 shall be set to (0) and bits 109-112 shall all be set to (0).
Table A2: IMO Maritime Emergency Codes
Code
Definition
0000
undesignated
0001
fire/explosion
0010
flooding
0011
collision
0100
grounding
0101
listing, in danger of capsizing
0110
sinking
0111
disabled and adrift
1000
abandoning ship
1001
undesignated
1010
undesignated
1011
undesignated
1100
undesignated
1101
undesignated
1110
undesignated
1111
test
A4.0 - LONG MESSAGE (OPTIONAL)
The optional long message format permits the inclusion of an additional 32 bits of information in bit positions 113 through 144 of the data message.
The maritime/location protocol (identified by protocol flag bit 26 - 0) will use these 32 bits as follows:
Bits
Usage
113-121
Course (in degrees true); range: 0 to 359
122-126
Speed (knots); range: 0 to 31
127-139
Activation time
127-129
Day of week (000 - Sunday); range: 7 days
130-134
Hours; range: 0 to 23
135-139
Minutes (2-minute increments); range: 0 to 58
140-144
Optional national use
A -13.
The other user protocols (identified by protocol flag bit 26-1) will use these 32 bits as follows[*]:
Bits 113-114 define the 32 bit message encoding as follows:
00 - latitude/longitude flag
01 - spare
10 - spare
11 - spare
For the latitude/longitude message, bits 115 through 144 are decoded as follows:
Bits
Usage
115-121
degrees latitude
122-127
minutes latitude
128
0-north; l-south
129-136
degrees longitude
137-142
minutes longitude
143
0-east; l-west
144
even parity bit applied to bits 113-143
The message-format flag (bit 25) should normally be set to -0 and a short message be transmitted, but it should be switched automatically to -1 when data is entered in bits 113 to 144 for the long-message transmission. This will require two separate BCH codes: one for use with message-format flag -0 (short-message format), and one for use with message-format flag -1 (long-message format).
B - 1
ANNEX B - BEACON MEASUREMENT METHODS
B1.0- GENERAL
The type of testing required by COSPAS-SARSAT is described in the Type Approval Document (C/S T.007). This Annex describes accepted measurement methods for the parameters defined in Section 2 of the beacon specification. An example of a test bench capable of implementing these measurement methods is shown in Figure B1. These are not necessarily the only methods for measuring parameters. Alternative measurement techniques can be approved by COSPAS-SARSAT, providing there is sufficient justification. Beacon manufacturers can use any other methods that they feel are representative of those used in actual certification tests.
B2.0 - PRINCIPLE OF OPERATION OF THE TEST BENCH
The particular characteristics of the COSPAS-SARSAT 406 MHz beacon require the use of special test equipment (STE) in addition to standard measurement instruments (e.g. frequency counter, spectrum analyser, etc.)
The message transmitted by the beacon is detected by a receiver which supplies ail the signals to be measured. Synchronization signals are generated by the STE which define the measurement intervals S1 , S2 and S3 as shown in Figure B2.
B3.0 - MEASUREMENT METHODS
B3.1 Message Format and Structure
B3.1.1 Repetition Period
The repetition period, Tr, between the beginnings of two successive transmissions (see Figure B3) shall be randomized with a uniform distribution over the range 47.5 to 52.5 seconds ( see section 2.2.1). Uniform distribution shall be determined from successive measurements over a five-minute period.
B3.1.2 Duration of the Unmodulated Carrier
The unmodulated carrier duration, T1, between the beginning of a transmission and the beginning of the data modulation shall satisfy the following relationship, where the mean value and the standard deviation are derived from 10 successive measurements:
158.4 ms < (T1 ± 3 sigma) < 161.6 ms (see section 2.2.3)
B3.1.3 Bit Rate and Stability
The bit rate, fb, which is measured over the first 50 bits corresponding to one transmission, shall satisfy the following relationship, where the mean value and the standard deviation are derived from 10 successive measurements:
The S1 pulse starts 12ms after the beginning of the unmodulated carrier.
The S2 pulse starts with bit 23.
The S3 pulse starts 15ms after the end of S2.
Figure B2: Definition of Measurement Intervals
Image unavailable in extracted text
Figure B3 : Transmission Timing
B -4
B3.1.4 Message Coding
The content of the digital message is checked against the one provided by the manufacturer. The compliance with the format for each data field is checked bit by bit.
The correctness of the error-correcting code is also checked.
B3.2 Modulator and 406 MHz Transmitter
B3.2.1 Transmitted Frequency (see Section 2.3.1)
B3.2.1.1 Nominal Value
The mean transmission frequency, f0, is determined from 10 measurements of fi (1) made during the interval S1 during 10 successive transmissions as follows:
Image unavailable in extracted text
B3.2.1.2 Short-Term Stability
The short term frequency stability is derived from measurements of f1(2) and f1(3) made during the intervals S2 and S3 during 10 successive transmissions as follows:
Image unavailable in extracted text
The above relationship corresponds to the Allan variance. The measurement conditions used here are different (i.e. dead time between two measurements). Experience, however, has shown that the results obtained are very close to those achieved under the normal measurement conditions for the Allan variance.
To correctly measure the short-term frequency stability, and to avoid an error which might result from an unequal number of negative and positive phase transitions occurring during the 100 ms gating interval of a frequency counter used in the internal gate mode, the 406 MHz beacon test bench, which demodulates the 400 bps bit stream, must use the bit clock to generate a gating signal of about 100 ms (± 1%) which contains the same number of positive and negative phase transitions. This gating signal is used with a frequency counter (e.g. HP 5345) in the external gating mode.
B -5
B3.2.1.3 Medium-Term Stability
The medium-term frequency stability is derived from measurements of fi(2) made over successive transmissions at instants fi for a period of 15 minutes (see Figure B4).
For a set of n measurements, the medium-term frequency stability is defined by the mean slope of the least-squares straight line and the residual frequency variation about that line.
The mean slope is given by:
Image unavailable in extracted text
The ordinate at the origin of the least-squares straight line is given by:
Image unavailable in extracted text
The residual frequency variation is given by:
Image unavailable in extracted text
With a transmission repetition period of 50 seconds, there will be 18 measurements during the 15 minute period (i.e. n-18).
B - 6
Image unavailable in extracted text
Figure B4: Medium-Term Frequency Stability Measurement
B - 7
B3.2.2 Power Output (see Section 2.3.2)
B3.2.2.1 Transmitter Power Output Level
The transmitter power output level is measured at the transmitter output.
B3.2.2.2 Stability During Transmission, Rise and Fall Times
The power stability and the rise and fall times are determined on an oscilloscope.
B3.2.2.3 Equivalent Isotropic Radiated Power
Antenna characteristics should be measured in a configuration as close as possible to its operational configuration.
B3.2.2.4 Spurious Output
The spurious levels are checked on a spectrum analyzer.
B3.2.3 Data Encoding and Modulation
The data encoding, the modulation sense, the modulation index and the modulation rise and fall times are checked with an oscilloscope on the biphase logic signal.
The modulation rise and fall times, ΊR and ΊF are defined in Figure 2.5.
B3.3 Voltage Standing Wave Ratio
The following characteristics will be verified after the transmitter load has been changed to both open circuit and short circuit at maximum, minimum and ambient temperatures:
- Transmitter nominal frequency
- Power output
- Spurious output
- Digital message content and modulation
The same characteristics, except for power output, will be verified for a VSWR of 3:1.
B3.4 Protection Against Continuous Transmission
If possible, the protection against continuous transmission will be checked by inducing a continuous transmission from the beacon under test. However, if the beacon manufacturer feels that this test is not feasible for his beacon, he must provide a technical explanation which demonstrates that his design complies with the specification.
END OF THIS SECTION
_________
COSPAS-SARSAT SECRETARIAT
INMARSAT, 40 Melton Street, London NWI 2EQ, England, United Kingdom.
Telephone: National 01-387 9089, International + 44 1 387 9069.
Telex 297201 INMSAT G Facsimile (G2-3) +44 1 383 7480 or 44 1 387 2115.
END OF REPRODUCTION
NOTE
1. Notified in the Commonwealth of Australia Gazette on 27 February 1990.
[*] This does not apply to the 406 MHz time calibration beacon transmitting from Toulouse, France.