Tekniske bestemmelser for Aeronautiske COSPAS-SARSAT positionsbestemmende nødradiofyr (ELT)

Bilag 1

Bilag 1 til TB 96 082

Applicable parts of EUROCAE

MINIMUM OPERATIONAL PERFORMANCE SPECIFICATION

FOR AIRCRAFT EMERGENCY LOCATOR TRANSMITTERS

(121.5/243 MHz and 406 MHz)

ED-62 Mai 1990

1.2 TYPES OF ELT

1.2.1 Four basic types of ELT are described in this document. They are

Automatic Fixed (ELT (AF)), Automatic Portable (ELT (AP)), Survival (ELT (S)) and Automatic Deployable (ELT (AD)).

The use of the suffix "Automatic" is for editorial purpose and is not intended to preclude the design, manufacture or use of manually activated ELTs. The requirement for and approval of automatic or manual activation methods is the prerogative of individual approval authorities.

In applying these minimum operational performance specifications to manually activated ELT equipments, all reference to automatic activation methods and crash sensors should be ignored. In all other respects, the specifications contained in this document shall apply to all ELTs, whether manually or automatically activated.

1.2.1.1 Automatic Fixed (ELT (AF))

This type of ELT is intended to be permanently attached to the aircraft before and after a crash.

1.2.1.2 Automatic Portable (ELT (AP))

This type of ELT is intended to be rigidly attached to the aircraft before a crash, but readily removable from the aircraft after a crash. It may also function as an ELT (AF) during the crash sequence. If the ELT does not include an integral antenna, the aircraft-mounted antenna may be disconnected and an auxiliary antenna (stored on the ELT case) connected in its place. The ELT can be tethered to a survivor or a life raft.

1.2.1.3 Survival (ELT (S))

This type of ELT is intended to be removed from the aircraft, deployed and activated by survivors of a crash. It can be tethered to a life raft or a survivor. Activation of an ELT (S) is usually by manual means but automatic activation (eg: by water activation) may apply.

1.2.1.4 Automatic Deployable (ELT (AD))

This type of ELT is intended to be rigidly attached to the aircraft before a crash and ejected and deployed

a. manually (during the crash sequence), or

b. automatically (after the crash sensor has determined that a crash has occurred).

3 MINIMUM PERFORMANCE SPECIFICATIONS UNDER STANDARD TEST CONDITIONS

3.1 MINIMUM PERFORMANCE SPECIFICATION - 121.5/243 MHz ELT

3.1.1 Operating Frequencies

3.1.1.1 The operating frequencies shall initially be set at

a. 121,5 MHz±6 kHz, and

b. 243,0 MHz±12 kHz.

3.1.1.2 The transmitted medium term frequency stability shall be defined by the mean slope of the frequency vs time over a 15 minute period and by the residual frequency deviation about the mean slope. The mean slope shall not exceed 0.2 parts/million/minute. The RMS frequency deviation about the mean slope shall not exceed 0.5 parts/million.

3.1.2 Modulation Characteristics

3.1.2.1 The rf carriers shall be amplitude modulated. The modulation factor shall be at least 0.85 but shall not exceed 1.0. (see Figure 3-1).

NOTE: The figure specified for modulation factor assumes a sinusoidal modulating signal. If the waveform of the modulating signal is other than sinusoidal, the modulation factor due to the fundamental component of the modulating signal shall be at least 0.85.

3.1.2.2 The frequency of the modulating signal shall sweep DOWNWARDS over a range of not less than 700 Hz within the limits of 1 600 Hz to 300 Hz with a sweep repetition rate between 2 Hz and 4 Hz.

NOTE: If the 121.5/243.0 MHz ELT is part of a combined unit with a 406 MHz locator beacon, the frequency of the modulating signal may optionally sweep UPWARDS over the same range and within the same limits and repetition rate as specified in 3.1.2.2.

3.1.2.3 The modulation signals applied to the carriers shall have a minimum duty cycle of 33% and a maximum duty cycle of 55%. (see Figure 3-2).

3.1.3. Emission Characteristics

3.1.3.1 The type of emission shall be A3A, as defined in the ITU Radio Regulations, and shall have one of the following characteristics

a. continuous carrier.

b. carrier keyed in such a manner that full power is applied to the antenna for one period, followed by reduced or zero power for a further period.

The ON/OFF cycle shall be optimised to allow the precise location of the beacon in all weather conditions and to ensure compatibility with all VHF homing equipment currently in service.

NOTE: It has been shown that an ON period of 0.75 seconds followed by an OFF period of 1.5 seconds gives satisfactory results.

3.1.3.2 The ELT shall have clearly defined sideband components which are symmetric about the output signal spectrum and distinct from the carrier component at both the 121.5 MHz and 243.0 MHz frequencies.

The ELT spectrum at 121.5 MHz shall have at least 30% of its energy distribution within a bandwidth of plus and minus 30 Hz about a fixed reference frequency corresponding to the carrier component over the audio/sweep modulation cycle.

At 243 MHz 30% of the energy distribution shall fall within a bandwidth of fc ±60 Hz.

3.1.3.3 To aid SAR system detection and homing capabilities, the transmission may also provide a period of unmodulated CW power for a duration of 2.0 (±0.25) seconds, repeated every 8.0 (±0.8) seconds.

3.1.3.4 Voice modulation, (A3E), is permitted provided that its use shall not prejudice the primary function of the beacon and power shall not be consumed at a greater rate than in the beacon mode.

Such equipment shall also comply with the following requirements

the equipment shall be clearly marked to caution operators to use the speech facility only when the rescue craft is seen or heard

where a speech facility is provided on 121.5/243 MHz the Trans-mitter /Receiver key must revert to beacon operation when not actually being keyed.

where a second, auxiliary speech channel is provided it must ope-rate on 123.1 MHz, (scene of the search frequency), and shall provide the same reversion to Beacon mode on 121.5/243 MHz as in b. above.

the Operator Instruction Manual must warn the user that when the speech facility is used, the homing capability is severely restricted or non-existent.

3.1.3.5 An identification signal is permitted using the International Morse Code. If this option is incorporated,

the identification signal shall consist of 5 or 6 letters, (the aircraft registration), at a repetition rate of once per minute;

the carrier shall be modulated A3A by 1 020 (±50) Hz;

the keying rate shall be as follows.

1 dot = 115 ±10) ms

1 dash = 3 dots

space between morse digits = 1 dot

space between coded letters = 1 dash

3.1.4 Antenna Radiation Characteristics

The antenna shall radiate on 121.5 MHz and 243.0 MHz. Radiation shall be vertically polarized and omni-directional in the horizontal plane.

3.1.5 Equivalent Isotropic Radiated Power

The Equivalent Isotropic Radiated Power (EIRP) shall not be less than -10 dBW (100 mW) or greater than -4 dBW (400 mW), on each frequency.

NOTE: Where it is required to establish Equivalent Isotropic Radiated Power it may be taken as the output power at the transmitter terminal, minus feeder and mismatch losses, plus average aerial gain relative to an isotropic radiator in the horizontal direction, or

EIRP (dBW) = PT - L + GA,

where

PT = transmitter output power, (dBW)

L = feeder and mismatch losses, (dB)

GA = aerial gain, (dB)

3.1.7 Radio Frequency Intermodulation

(Does not apply to ELT (S))

When the ELT unit is in the ARMED mode, the application of any two frequencies in the 54 MHz - 806 MHz band to the ELT shall not result in reradiation of at third frequency in the 108 MHz - 137 MHz band which exceeds the levels specified in paragraphs 3.1.7.1 and 3.1.7.2 below, under the associated specified conditions.

3.1.7.1 Direct Coupling

With the ELT connected in the configuration shown in Figure 3-3, and the levels from each generator into the ELT rf output terminal equal to the levels indicated in Table 5-1 of paragraph 5.2.7, the third frequency shall not exceed -83 dBm.

3.1.7.2 Radiation Coupling

With the ELT mounted in a typical aircraft configuration and the test set-up as shown in Figure 3-4, the application of vertically polarised electromagnetic fields, which have an electric field intensity equal to the levels, specified in Table 5-2 of paragraph 5.2.7, to the external surface of the aircraft test configuration shall not result in a third field with an intensity greater than 7 microvolts/meter in the 108 MHz - 37 MHz band, at a suitable receiving antenna placed 2 metres from the ELT antenna.

3.1.9 Transmitter Turn-on

At the maximum and minimum operating temperatures, the EIRP level at each carrier frequency shall not be less than 20 dBm (100 mW), within 5 minutes following manual or automatic activation.

3.2 406 MHz ELT

3.2.1 Operating Frequency

3.2.1.1 The operating frequency shall initially be set at 406.025 MHz ±2 kHz.

3.2.1.2 The transmitted frequency shall not vary more than ±5 kHz in five years including the initial offset.

3.2.1.3 It shall not vary more than 0.002 parts/million/100 milliseconds.

3.2.1.4 The transmitted medium-term frequency stability shall be defined by the mean slope of the frequency vs time over a 15 minute period and by the residual frequency deviation about the mean slope. The mean slope shall not exceed 0.001 parts/million/minute. The RMS frequency deviation about the mean slope shall not exceed 0.003 parts per million.

3.2.1.5 For ELTs manufactured prior to 1 January 1991, relaxation of the requirements regarding medium-term stability is acceptable as follows

the mean slope shall not exceed 0.002 parts/million/minute

the residual frequency variation about the mean slope shall not exceed 0.005 parts/million.

3.2.2 Digital Message Generator

The digital message generator shall key the modulator and transmitter so that the message defined in C/S T.001* is transmitted.

* "Specifications for COSPAS-SARSAT 406 MHz Distress Beacons".

3.2.2.1 Repetition Rate

The period between transmissions shall be 50 sec ±5%. The repetition rate shall be jittered so as not to be so stable that any two transmitters appear to be synchronised closer than a few seconds over a 5 minute period.

An acceptable alternative for a production run is an equal distribution of fixed repetition periods of 8 or more values, approximately equally spaced, over the range of 47.5 seconds to 52.5 seconds.

3.2.2.2 Total Transmission Time

The total transmission time shall be 440 ms ±1%, for the standard short message, and 520 ms ±1% for the optional long message.

3.2.2.3 CW Preamble

The initial 160 ms ±1% of the transmitted signal shall consist of an unmodulated carrier at the transmitter frequency measured at the 90% power point.

3.2.2.4 Digital Message

Short Message

The final 280 ms ±1% of the transmitted signal shall contain a 112 bit message at a bit rate of 400 bps ±1%.

Long Message (optional)

The final 360 ms ±1% of the transmitted signal shall contain a 144 bit message at a bit rate of 400 bps ±1%.

3.2.2.5 Bit Synchronisation

A bit synchronisation pattern consisting of "1's" shall occupy the first 15 bit positions.

3.2.2.6 Frame Synchronisation

A frame (or message) synchronisation pattern consisting of 9 bits shall occupy bit positions 16 through 24. The frame synchronisation pattern shall be 000 101 111. During Self-Test operation, the frame synchronisation pattern shall be 011 010 000.

3.2.2.7 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.

3.2.2.8 Message Structure

The structure of the remaining 87 bits (short message) and 119 bits (long message) is defined in C/S T.001.

3.2.3 Modulation

3.2.3.1 The carrier shall be phase modulated 1.1 (±0.1) radians, peak, referenced to an unmodulated carrier. Modulation sense shall be as shown in Figure 3-5.

3.2.3.2 Rise and fall times of the modulation waveform shall be greater than 50 microseconds and less than 250 microseconds. Rise and fall times are defined as the time duration between the 0.9 points of the peak to peak phase transition on the waveform of Figure 3-6.

3.2.3.3 Modulation symmetry (see Figure 3-7) shall be such that

x T1 - T2x

# 0.05 (max)

T1 + T2

3.2.4 Data Encoding

The data shall be encoded biphase L. (see Figure 3-5).

3.2.5 Equivalent Isotropic Radiated Power, (EIRP)

3.2.5.1 The EIRP of the transmitted pulse shall be 6 dBW ±4 dB, where

EIRP = PT - L + GA and

PT = Transmitter output (dBW)

L = feeder and mismatch losses (dB)

GA = antenna gain, (dB)

Note; This specification meets the signal requirements of the COSPAS/SARSAT Specification C/S T.001.

C/S T.001 specifies transmitter output power into an antenna of defined characteristics.

This Minimum Operational Performance Specification specifies performance in terms of EIRP which is performance related rather than design oriented. The manufacturer is thus allowed a greater degree of flexibility in meeting the performance requirements by means best suited to individual design. Note, however, that the above EIRP requirement is a more demanding performance specification than that defined in C/S T.001 and equipment designed to C/S T.001 may not satisfy the requirements of this Minimum Operational Performance Specification.

3.2.5.2 The transmitter output power rise time shall be less than 5 ms, measured between the 10% and 90% power points.

3.2.6 Antenna Radiation Characteristics

3.2.6.1 The stated EIRP shall obtain over 90% of the following range.

Azimuth: 360o Elevation: 5o to 60o

3.2.6.2 Polarisation shall be circular (RHCP) or linear.

3.2.7 Abnormal Transmitter Loads

The modulator and 406 MHz transmitter shall meet all the requirements of this MOPS, except for those in paragraph 3.2.5 (EIRP), when the transmitter is terminated with a load mismatched from the design impedance by a factor of 3, and shall not be damaged by any load from open circuit to short circuit.

3.2.8 Maximum Continuous Transmission

The 406 MHz ELT shall be designed to limit any continuous transmission caused by equipment failure to a maximum of 45 seconds.

3.2.9 Spurious Emissions and Carrier Harmonics

3.2.9.1 The limits of spurious emissions measured against the level of the unmodulated carrier shall be as shown in Figure 3-8.

3.2.9.2 Carrier harmonics shall be at least 30 dB below the level of the unmodulated carrier.

3.2.10 Radio Frequency Susceptibility

When the ELT unit is in the ARMED mode, it shall not be activated or damaged when a signal in the bands 88 MHz to 137 MHz and 420 MHz to 460 MHz (excluding the band 121 MHz to 122 MHz) at a level of +23 dBm is directly coupled to the ELT antenna terminal.

4.4 GROUP A TESTS

4.4.1 Temperature (Activation) and Altitude

The following test procedures for temperature and altitude shall be used in lieu of those specified in ED-14C/DO-160C, Section 4.0.

4.4.1.1 Low Temperature (Activation) (SPECIAL)

a. The ELT shall be switched to ARMED, (or OFF in the case of an ELT (S)). The unit shall then be placed in the temperature test chamber and allowed to stabilise at -55o C.

b. The test chamber temperature shall then be increased to -40oC (Class 1 equipment), or -20oC (Class 2 equipment), and the unit temperature allowed to stabilise.

c. The ELT shall then be removed from the test chamber and, within a period of two minutes, activated by one of the following methods.

(1) If the unit is water-activated, immerse in water at 0oC until it activates.

(2) If the unit is manually activated, activate the unit using the ON switch.

(3) If a crash acceleration activation sensor is used subject the unit to a single shock pulse of amplitude = 3 (±0.3) "g", and velocity change (delta V)* = 1.35 m s-1 (4.5 f s-1) ±10%

(Velocity change shall be determined using a procedure similar to that outlined in Figure 4-1)

* (as defined in Appendix B)

(4) If a frangible switch or other device is used for crash sensing, an appropriate test shall be devised to ensure that the activation mechanism operates correctly at the low temperature limit.

d. Fifteen minutes after activation, the ELT shall be tested for compliance with the requirements of the following paragraphs.

121.5/243 MHz 406 MHz

Control and Monitor 2.5 2.5

Self-Test 2.6.1 2.6.1

Operating Frequency 3.1.1.1 3.2.1.1

EIRP 3.1.5. 3.2.5

e. At the completion of the test, ensure that all mechanical devices operate satisfactorily.

4.4.1.2 High Temperature (Activation) (SPECIAL)

The ELT shall be switched to ARMED, (or OFF in the case of an ELT (S)). The unit shall then be placed in the temperature test chamber and allowed to stabilise at +85oC.

The test chamber temperature shall then be reduced to +55oC, and the ELT allowed to stabilise.

The ELT shall then be removed from the test chamber and activated, within a period of two minutes, by one of the following methods.

(1) If the unit is a water-activated ELT, then immerse in water at +40oC until it activates.

(2) If the unit is a manually activated ELT, then activate the unit using the ON switch.

(3) If a crash acceleration sensor is used, subject the unit to a single shock pulse of amplitude = 3 (±0.3) "g", and velocity change (delta V)* = 1.35 m s-1 (4.5 f s-1) ±10%

* (as defined in Appendix B)

(Velocity change shall be determined using a procedure similar to that outlined in Figure 4-1)

(4) If a frangible switch or other device is used for crash sensing, an appropriate test shall be devised to ensure that the activation mechanism operates correctly at the high temperature limit.

d. Fifteen minutes after activation, the ELT shall be tested for compliance with the requirements of the following paragraphs.

121.5/243 MHz 406 MHz

Control and Monitor 2.5 2.5

Self-Test 2.6.1 2.6.1

Operating Frequency 3.1.1.1 3.2.1.1

EIRP 3.1.5. 3.2.5

e. At the completion of the test, ensure that all mechanical devices operate satisfactorily.

4.4.4 Vibration (ED-14C/DO-160C, Section 8.0)

4.4.4.1 After being subjected to this test,

the ELT shall not have activated,

establish compliance with the requirements of the following paragraphs

121.5/243 MHz 406 MHz

Control and Monitor 2.5 2.5

Self-Test 2.6.1 2.6.1

Operating Frequency 3.1.1.1 3.2.1.1

EIRP 3.1.5. 3.2.5

4.4.4.2 At the completion of this test, ensure that all mechanical devices operate satisfactorily.

4.4.13 Emission of Radio Frequency Energy (ED-14C/DO-160C, Section 21.0)

4.4.13.1 121.5/243 MHz ELT

Establish compliance with the requirements of the category to which the equipment is declared.

4.4.13.2 406 MHz ELT

Establish compliance with the requirements of paragraph

3.2.9 Spurious Emissions and Carrier Harmonics.

4.6.1 Low Temperature (Operation) (SPECIAL)

4.6.1.1 The ELT shall be switched to ARMED, (or OFF in the case of an ELT (S), placed in the temperature test chamber and allowed to soak at -550C for at least 3 hours.

4.6.1.2 The test chamber temperature shall then be increased to -400C (Class 1 equipment), or -200C (Class 2 equipment), and the unit allowed to stabilise.

4.6.1.3 The ELT shall be manually activated. Removal from the chamber to enable activation, shall not be for a period greater than 2 minutes.

4.6.1.4 The ELT shall be tested for compliance with the requirements specified below at the following periods

Fifteen minutes after activation, then

once every six hours until, and including,

at the end of the periods specified in paragraphs 3.1.6 and 3.2.12.

21.5/243 MHz 406 MHz

Control and Monitor 2.5 2.5

Self-Test 2.6.1 2.6.1

Operating Frequency 3.1.1.1 3.2.1.1

EIRP 3.1.5. 3.2.5

4.6.1.5 At the completion of this test, ensure that all mechanical devices operate satisfactorily.

4.6.2 High Temperature (Operation) (SPECIAL)

4.6.2.1 Fresh batteries may be installed before performing this test.

4.6.2.2 The ELT shall be switched to ARMED, (or OFF in the case of an ELT (S)), placed in the temperature test chamber and allowed to soak at +85 for at least 3 hours.

4.6.2.3 The test chamber temperature shall then be reduced to +550C, and allowed to stabilise.

4.6.2.4 The ELT shall be manually activated. Removal from the chamber to enable activation shall not be for a period greater than 2 minutes.

4.6.2.5 The ELT shall be tested for compliance with the requirements of the paragraphs specified below at the following periods.

Fifteen minutes after activation, then

once every six hours, until, and including,

at the end of the periods specified in paragraphs 3.1.6 and 3.2.12.

121.5/243 MHz 406 MHz

Self-Test 2.6.1 2.6.1

Operating Frequency 3.1.1.1 3.2.1.1

EIRP 3.1.5. 3.2.5

4.6.2.6 At the completion of this tests, ensure that all mechanical devices operate satisfactorily.

ELECTRICAL TEST PROCEDURES

5.1 GENERAL REQUIREMENTS

5.1.1 Shielded Room and Test Transmissions

Unless otherwise specified, ELT testing must be conducted in a shielded room or metal enclosure. Bench and ground tests conducted outside of a shielded room should not be performed on 121.5 MHz or 243.0 MHz; off-set crystals MUST be used. Test transmissions on 406 MHz must have a frame synchronisation pattern of 011 010 000 to ensure that the signals are not processed by the COSPAS-SARSAT satellites.

5.1.2 Power Input Voltage

Unless otherwise specified, all tests shall be conducted with the ELT using its self-contained battery connected in the normal mode of operation. The voltage, of external power supplies, eg: to Control and Monitor system(s), shall be adjusted to the declared design voltage ±5% and shall be measured at the equipment input terminals.

5.1.3 Adjustment of Equipment

The circuits of the equipment under test shall be properly aligned and adjusted in accordance with the manufacturer s recommended practice prior to application of the specified tests.

5.1.4 Test Instrument Precautions

Precautions shall be taken while carrying out the tests to prevent the introduction of errors resulting from the improper connexion of test instruments to the equipment under test.

5.1.5 Ambient Conditions

Unless otherwise specified, all tests shall be conducted under conditions of ambient room temperature, pressure and humidity, as defined in ED-14C/DO-160C, paragraph 3.4.

5.1.6 Connected Loads

Unless otherwise specified, all tests shall be performed with the equipment connected to loads having the impedance values for which it is designed.

5.1.7 Warm-up Period

Unless otherwise specified, all tests shall be conducted after a warm-up period of not less than 5 minutes.

5.1.8 Recording of Test Results

When test results are being recorded for inclusion in the type test report, it is not sufficient to note merely that the requirement was met. Except where tests are obviously CO/NO-GO in character, (eg: determination of whether or not mechanical devices function correctly), the actual numerical values obtained for each of the parameters tested shall be recorded.

5.1.9 Test Procedures

5.1.9.1 The following test procedures are considered to be a satisfactory means of determining required performance under standard and stressed environmental conditions.

5.1.9.2 Although test procedures are specified, it is recognised that other methods may be preferred. Such other procedures may be used if the manufacturer can show that they provide at least equivalent information. The procedures described in this chapter should be used as criteria in evaluation the acceptability of alternative procedures.

5.2 DETAILED TEST PROCEDURES - 121.5/243.0 MHZ ELT

5.2.1 Equipment Required

Power Meter Pulse Generator

Signal Generator Envelope Detector

VHF Receiver Diplexer

Frequency Counter Detector

Amplifier Oscilloscope (Storage)

Field Intensity Meter (FIM)

5.2.2 Operating Frequencies (Paragraph 3.1.1)

Connect the equipment as shown in Figure 5-1. Operate the equipment, using its own power supply and terminated with the nominal load impedance. Measure the carrier frequencies of the 121.5 MHz and 243.0 MHz emissions to an accuracy of at least five parts per million (Figure 5-2).

5.2.3 Modulation Characteristics (Paragraph 3.1.2)

5.2.3.1 Operate the equipment as in 5.2.2.

5.2.3.2 Observe the modulation envelope on the storage oscilloscope and determine the upper and lower audio frequency sweep limits, sweep rate and modulation factor.

5.2.4 Modulation Duty Cycle (Paragraph 3.1.2)

5.2.4.1 Operate the equipment as in 5.2.2.

5.2.4.2 Observe the detected modulation envelope indicated on the storage oscilloscope and determine the modulation duty cycle.

5.2.5 Transmitter Duty Cycle (Paragraph 3.1.3)

5.2.5.1 Operate the equipment as in 5.2.2.

5.2.5.2 Observe the modulated signal and determine that the carrier is not interrupted between sweeps.

5.2.6 Equivalent Isotropic Radiated Power (Paragraph 3.1.5)

5.2.6.1 Test Conditions

The test site should be on level ground which has uniform electrical characteristics. The site should be clear of metal objects, overhead wires, etc., and as free as possible from interfering signals such as ignition noise or other rf carriers.

The distance from the transmitter under test, or the field intensity meter, to reflecting objects such as rain gutters or house plumbing should be at least 100 metres.

ELTs (AF) and (AP) should be placed on or inside a non-metallic test structure in a configuration representing a typical aircraft installation at a height of 1.3 metres above the ground.

ELTs (AD) and (S) should be placed on the ground with a supplementar y ground plane.

Measurement of radiated or received signals should be made at a point 30 metres from the antenna. At this point, a wooden pole or insulated tripod with a movable horizontal boom should be arranged so that the search antenna of the FIM can be raised an lowered through an elevation of half a wave- length. The FIM search antenna should be mounted on the end of the boom with its cable lying horizontally on the boom back to the supporting mast. The FIM is placed on a suitable tripod at the foot of the mast.

For each frequency measurement, the FIM antenna should be adjusted to the correct length for the frequency involved.

5.2.6.2 Test Method

The basic method of measuring the EIRP is that of direct substitution as detailed below.

Place the standard quarter-wavelength monopole antenna on a ground plane with a minimum dimension of half a wave-length radius.

Connect a calibrated signal generator set for the power required in paragraph 3.1.5. (Account for all losses in transmission lines and impedance mismatch at the antenna to ensure that the transmitted signal is not less than that specified in paragraph 3.1.5, "Equivalent Isotropic Radiated Power").

Place the FIM antenna in a vertical position with the lower element tip at least one quarter-wavelength above the ground.

Measure the field strength with the FIM in "peak position". The FIM antenna may be rotated about its centre axis for a maximum reading, (vertical to horizontally polarised reception).

For ELTs with externally mounted antennas, replace the standard quarter-wavelength antenna and its calibrated source with the ELT.

For ELTs with an integrally mounted antenna replace the standard quarter-wavelength antenna, ground plane and calibrated source with the ELT system mounted inside a representative mockup of a standard installation, (i.e. a mockup of the aircraft fuselage with seats and windows), or, for antennas mounted within a fincap, a representative mockup of the aircraft vertical stabiliser.

Measure the field strength with the FIM in "peak" position. The FIM antenna may again be rotated for maximum signal. The height of the FIM antenna may also be adjusted for maximum signal. The ELT under test and test mockup should be rotated to obtain field strength measurements at least every 10 degrees of azimuth. The pattern should be essentially omni-directional in the horizontal plane. The pattern deviation shall not be greater than 6 dB from the reference signal at any selected point. The average of four evenly spaced field strength readings shall be equal to, or greater than, the standard.

Repeat a. through g. above for each of the two radiated frequencies involved.

5.2.7 Radio frequency intermodulation (paragraph 3.1.7)

(Does not apply to ELT (S))

5.2.7.1 Reradiated rf intermodulated signals may be measured using 5.2.7.3 or 5.2.7.4, below, as appropriate. If the ELT incorporates a non-linear device, (eg; a diode) in the antenna configuration external to the ELT transmitter unit, then procedure d. shall be used. The ELT shall be in the ARMED mode for these tests.

5.2.7.2 Equipment required

RF Signal Generator (3) Attenuator

Hybrid Power Divider Field Intensity Meter

Resistive Power Divider Power Meter

Spectrum Analyser RF Amplifier (2)

Variable Notch Filter (2)

5.2.7.3 Direct coupling method

The ELT shall be connected as shown in Figure 3-3. To demonstrate the compliance, the test frequencies specified in Table 5-1 may be used. The power level into the ELT at each frequency should be as indicated in Table 5-1, which considers the ELT antenna gain loss at the measured interference frequency.

All equipment should have at least a 15-minute warm-up period.

The series-connected notch filters should be capable of attenuating the interfering frequency signal by a minimum of 30 dB and the RFI by not more than 15 dB.

All signal generators shall be set to the CW mode.

Test procedure

(1) Adjust the signals from two signal generators to the frequencies indicated in Frequency Set A of Table 5-1.

(2) Adjust the notch filters to attenuate the interference signals by at least 30 dB.

(3) Reduce the signal from the two signal generators to a minimum. Connect a third signal generator to the output of the 3 dB attenuator. Set Signal Generator 3 to the RFI frequency expected in the 108 MHz-137 MHz band and adjust the generator output level to -83 dBm. Verify that the signal can be seen on the spectrum analyser and note its amplitude. Repeat this procedure for all RFI frequencies that could be expected. If the signal cannot be seen on the spectrum analyser, the notch filters may have to be readjusted.

(4) Disconnect Signal Generator 3. Increase the output from Signal Generators 1 and 2 to the test level. Verify that the two interference frequencies are still attenuated by 30 dB or more.

(5) Reduce the signal from Signal Generator 2 to a minimum. Connect the power meter to the 3 dB attenuator. Adjust the output of Signal Generator 1 until the power meter measures the level specified in Table 5-1.

(6) Repeat step 5 with the signal from Signal Generator 1 reduced to a minimum and the signal from Signal Generator 2 at the test level.

(7) Increase the signal from Signal Generator 1 to the test level. Disconnect the power meter. Connect the ELT to the 3 dB attenuator. Record the maximum deflections on the spectrum analyser in the 108 MHz-137 MHz band. To meet the requirement these deflections shall be less than those noted in step 3.

(8) Repeat steps 1-7 using the other frequency sets, ( B and C ), defined in Table 5-1.

5.2.7.4. Radiation method

The test set-up should be as shown in Figure 3-4. The test frequencies of Table 5-2 may be used.

All equipment should have at least a 15-minute warm-up period.

All signal generators should be set to the CW mode.

The ELT antenna(s) should be mounted in an aircraft configuration or mockup using metallic or non-metallic housings, as appropriate.

The ELT antenna and mock-up should be at a distance of D1 (minimum 12 metres). from its intended test position and from the transmitting antenna(s).

Test procedure

Frequency Set A (Table 5-2)

(1) Adjust the signals from two signal generators to the frequencies specified in Table 5-2.

(2) Place the FIM antenna in the ELT s intended position.

(3) Adjust the FIM to the frequency of Signal Generator 1 and adjust the output of Signal Generator 1 until the FIM measures the intensity indicated in Table 5-2. Record the output setting of Signal Generator 1.

(4) Repeat step 3 for Signal Generator 2.

(5) Place the ELT antenna and FIM antenna in their respective positions (Figure 3-4). For an internal antenna, use the external surface of the aircraft mock-up nearest the ELT antenna position.

(6) Adjust both signal generators to the outputs recorded in steps 3 and 4. Adjust the FIM to measure frequencies in the 108 MHz-137 MHz band. The field intensity measured by the FIM shall not be greater than 7 ?V m-1.

(7) Rotate the ELT antenna and mock-up and perform step 6 for each of the three remaining quadrants, (approximately 90 degree increments).

(8) Repeat steps 1-7 using the other frequency sets ( B and C ), defined in Table 5-2.

5.2.8 Radio Frequency Susceptibility (paragraph 3.1.8)

(does not apply to ELT (S)).

5.2.8.1 ELT susceptibility to rf damage or activation may be measured using the procedure described in paragraph 5.2.8.3 below.

5.2.8.2 Equipment Required

RF Signal Generator (3) Attenuator

Hybrid Power Divider RF Amplifier (2)

Resistive Power Divider Spectrum Analyser

Variable Notch Filter (2) Power Meter

Field Intensity Meter

5.2.8.3 Test Procedure

Adjust the signal generator to a frequency in the 108 MHz - 121 MHz band. Connect the rf amplifier and power meter and adjust the output of the signal generator to measure +23 dBm on the meter. The meter s input impedance should match the ELT antenna s terminal impedance.

With the ELT in the ARMED mode, replace the power meter with the ELT, and inject the +23 dBm signal into the ELT antenna terminal. After one minute, disconnect the ELT and determine that it has not activated.

Activate the ELT and determine compliance with the requirements of paragraph 4.4.10.

Repeat steps 1 through 3 for a frequency in the 122 MHz-137 MHz band.

5.2.9 Transmitter Turn-on (Paragraph 3.1.9)

This test should be performed in conjunction with the Low and High Temperature (Operating) tests in paragraphs 4.6.1 and 4.6.2.

5.2.9.1 For ELTs (AF), (AP) and (AD), the transmitter control shall be placed in the ARMED mode. The ELT should be activated by subjecting it to a shock pulse in accordance with paragraph 5.4. Within a period of five minutes following application of the shock pulse, the transmitter shall radiate at full EIRP.

5.2.9.2 For ELT (S), the transmitter shall radiate at full EIRP within five minutes after the transmitter is turned on.

5.3 DETAILED TEST PROCEDURES - 406 MHZ ELT

5.3.1 General

The test procedures required by COSPAS-SARSAT are described in the COSPAS-SARSAT Type Approval Standard, (Document C/S T.007). This section describes accepted measurement methods for the parameters defined in Chapter 3 of C/S T 007. Different measuring techniques may be approved by COSPAS-SARSAT providing there is sufficient justification.

5.3.2 Test Bench

5.3.2.1 The particular characteristics of the COSPAS-SARSAT 406 MHz beacon require the use of special test equipment, (STE), in addition to standard measuring instruments, (eg: frequency counter, spectrum analyser, etc). Figure 5-3 shows an example of this test equipment set-up.

5.3.2.2 The message transmitted by the beacon is detected by a receiver from which all the parameters to be measured are obtained. Synchronisation signals are generated by the STE which define the measurement intervals S1, S2 and S3, as shown in Figure 5-4.

5.3.3 Transmitted Frequency (See Paragraph 3.2.1)

5.3.3.1 Nominal Value

The mean transmission frequency, fo, is determined from 10 measurements of fi(1) made during the interval S1 during 10 successive transmission as follows.

1 10

fo = f(1) = ― 3 fi (1)

10 i = 1

5.3.3.2 Short Term Stability

The short-term frequency stability is derived from measurements of fi(2) and fi(3) made during the intervals S2 and S3 during 10 successive transmissions as follows

1 10 fi (2) - fi (3)

σ100 ms = [ 3 ( ) 2 ] 1/2

20 i = 1 fi (2)

The above relationship is similar to the Allan variance. However, the measurement conditions used here are different, (i.e. dead time between two measurements). Experience has shown that the results obtained are very close to those achieved under the normal measurement conditions for the Allan variance.

In order to perform a correct measurement of the short-term frequency stability, and 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 in the external gating mode.

5.3.3.3 Medium Term Stability (see Figure 5-2)

The medium term frequency stability is derived from measurements of fi(2) made over successive transmissions at instants ti for a period of 15 minutes.

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 deviation about that line.

With a transmission repetition period of 50 seconds, there will be 18 measurements during the 15 minute period, (i.e. n = 18).

5.3.3.4 Long Term Drift Test

The ELT should be powered by an external power source during the test period. Unless otherwise specified, the test period should be 30 days.

The ELT should be turned ON and placed in a temperature chamber maintained at an aging temperature of 55 (±1)oC, (or at ambient temperature if the ELT oscillator is contained in an oven). The ELT should be allowed to stabilise for 48 hours at the aging temperature before beginning the data acquisition cycle.

The frequency of the ELT should be measured immediately after the stabilisation period. The frequency of the ELT should be measured at intervals of not greater than 20 hours. The data obtained should fit, using the method of least squares, the function

f(t) = A [ 1n (Bt + 1)] +fo

where f(t) is the output frequency of the ELT, t days after the start of the stabilisation period, (the time origin for data analysis should be the beginning of the stabilisation period), and A, B and fo are constants to be determined from the least square fit.

If the aging trend is not monotonic, the measurement period should be extended to 40 days after the frequency maximum, (or minimum), in the aging trend. For the total aging period of n days, the data for the last 28 days should be fit to the function shown in the above equation, and the beginning of the stabilisation period should be redefined to be n-30.

Using the above equation, the following conditions must be met.

fo = 406.025 (±0.002) MHz

f(30) - fo = ±0.0003 MHz

f(1 825) - fo= ±0.003 MHz*

*(Alternatively, the manufacturer may demonstrate that the initial offset plus temperature effects plus aging over 5 years is less than 0.005 MHz).

5.3.4 Message Format and Structure (see Figure 5-5)

5.3.4.1 Repetition Period

The repetition period, TR, between the beginnings of two successive transmissions, shall be random, in a uniform distribution, over the range from 47.5 seconds to 52.5 seconds, (see paragraph 3.2.2). Uniform distribution shall be determined from successive measurements over a five minute period.

5.3.4.2 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 r < 161.6 ms (see paragraph 3.2.2)

5.3.4.3 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.

396 bps < fb ±3 r < 404 bps (see paragraph 3.2.2)

5.3.4.4 Message Coding

The content of the digital message is checked with 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.

5.3.4.5 Data Encoding and Modulation

The data encoding, the modulation sense, the modulation index and the modulation rise time are checked by examining the biphase logic signal with an oscilloscope. The modulation rise time TR, is defined as shown in Figure 3-6 .

5.3.5 Radio Frequency Susceptibility (Paragraph 3.2.10)

5.3.5.1 ELT susceptibility to rf damage or activation may be measured using the procedure described below.

5.3.5.2 Equipment Required

RF Signal Generator (3) Spectrum Analyser

Hybrid Power Divider Power Meter Attenuator

Resistive Power Divider Field Intensity Meter

Variable Notch Filter (2) RF Amplifier (2)

5.3.5.3 Test Procedure

Adjust the Signal Generator to a frequency in the 108 MHz-121 MHz band. Connect the rf amplifier and power meter and adjust the output of the signal generator to measure +23 dBm on the meter. The meter s input impedance should match the ELT antenna s terminal impedance.

With the ELT in the ARMED mode, replace the power meter with the ELT, and inject the +23 dBm signal into the ELT antenna terminal. After one minute, disconnect the ELT and determine that it has not activated.

Activate the ELT and determine compliance with the requirements of Paragraph 4.4.10.

Repeat steps a. through c. for a frequency in each of the 122 MHz-137 MHz and 420 MHz to 460 MHz bands.

5.3.6 Abnormal Transmitter Load Test

5.3.6.1 Terminate the ELT into a short circuit and manually turn the ELT ON. After a minimum of one hour, remove the short circuit and ensure that the following equipment performance standards are met.

Nominal operating frequency;

EIRP;

Digital message (28- or 36-character hexadecimal).

5.3.6.2 Terminate the ELT with an open circuit. Manually turn the ELT ON. After a minimum of one hour ensure that the following equipment performance standards are met.

Nominal operating frequency;

EIRP;

Digital message (28- or 36-character hexadecimal).

5.3.6.3 Terminate the ELT into a load which presents a mismatch by a factor of 3 compared to the design output impedance. Manually turn the ELT ON and ensure that the following equipment performance requirements are met.

Nominal operating frequency;

Digital message (28- or 36-character hexadecimal).

Tekniske bestemmelser for Aeronautiske COSPAS-SARSAT positionsbestemmende nødradiofyr (ELT)i TB 96 082 December 1998

Gyldighedsområde

Disse tekniske bestemmelser specificerer de tekniske krav og tilhørende prøvningsforskrifter som aeronautiske COSPAS-SARSAT positionsbestemmende nødradiofyr (ELT) skal overholde, for at kunne typegodkendes.

Hjemmelsgrundlaget for disse tekniske bestemmelser fremgår af § 25 i Forsknings-ministeriets lov nr. 394 af 10. juni 1997 om radiokommunikation og tildeling af frekvenser.

Ikrafttræden

Disse tekniske bestemmelser træder i kraft 1. december 1998.

Typegodkendelse

Fremgangsmåden for opnåelse af typegodkendelse fremgår af § 5 i Forskningsministeriets bekendtgørelse nr. 957 af 12. december 1997.

Tekniske krav og prøvningsforskrifter

De tekniske krav med tilhørende prøvningsforskrifter, som radioanlægget skal opfylde, fremgår af bilag 1 til disse tekniske bestemmelser.

Rekvirering af love, bekendtgørelser, standarder m.v.

Tekniske bestemmelser samt relevante love og bekendtgørelser kan fås/købes ved henvendelse til Telestyrelsen, Holsteinsgade 63, 2100 København Ø, tlf: 35430333, fax: 35431434.

ETSI dokumenter ((I-)ETS er, EN er og TBR er) kan downloades fra ETSI s hjemmeside: eller rekvireres hos Telestyrelsen.

ITU rekommandationer m.v. kan købes direkte hos ITU, Place des Nations, CH-1211 Genève 20, tlf.: +41 22 730 5111, fax: +41 22 730 5194 eller +41 22 733 7256 eller eventuelt gennem Telestyrelsen.

Radiorelaterede rekommandationer herunder, ERC Decisions, Radiocommunication Reports, Report Forms og Application Forms, Recommendations on Radiocommunications kan købes hos: ERO, European Radiocommunications Office, Midtermolen 1, 2100 København Ø, tlf: 35250300, fax: 35250330. For yderligere information henvises til ERO s hjemmeside på internettet

ISO/CEN/CENELEC/IEC/DS standarder kan købes hos Dansk Standard, Kollegievej 6, 2920 Charlottenlund, tlf: 39966101, fax: 39966102.

Telestyrelsen, den 1. december 1998

i I overensstemmelse med bestemmelserne i direktiv 98/34/EØF, der kodificerer informationsproceduren 83/189, er disse tekniske bestemmelser notificeret over for Europa-Kommissionen under nr. 98/0220/DK