Report on Test Procedures and Measurements Results for the Development of Frequency Planning

AMCP WGB/11-WP4 Rev.1

Report on test procedures and measurement results for the development of frequency planning criteria for VDL Mode 4 Author: Dr. Armin Schlereth, DFS Date: 5th September 2001

Abstract

This document provides an overview on test procedures as agreed in ICAO/AMCP-WG-B and test results of measurement exercises conducted in DFS labs 6th of November to 1st of December 2000 and from 7th of May to 16th of August 2001. Further test results are from a measurement exercise at EUROCONTROL Experimental Centre in Bretigny, which took place from 12th to 14th of December 2000.

This report contains test data related to:

 VDL Mode 4 power spectrum measurements  VDL Mode 4 receiver sensitivity  VDL Mode 4 interference on VDL Mode 4  VDL Mode 4 interference on analog voice DSB-AM radios and vice versa This includes also a validation of the so called S/P 6 dB criteria. Comprehensive voice samples have been recorded in that context.  VDL Mode 4 interference on VDL Mode 2  VDL Mode 2 interference on VDL Mode 4, but only for –82 dBm input power value. Measurements for – 88 dBm input power value are still missing.  VDL Mode 4 interference on VOR  VDL Mode 4 interference on ILS

No data on impact of VDL Mode 4 on GBAS and vice versa could be gathered due to lack of GBAS equipment. As VDL Mode 4 units two radios from one manufacturer have been investigated in detail.

References:

[1] Voice-Interference Tests for VDL Mode 4; Dr. Armin Schlereth; AMCP/WG-D12-WP12; Jan. 2000 [2] Report to AMCP/WG-B: Frequency Planning Criteria for VDL Mode 4; VDL Mode 4 VSG; Sept. 1999 [3] AMCP/WG-B 8th Meeting Report; Jan. 2000 [4] AMCP/WG-B 9th Meeting Report; July 2000 [5] Preliminary general interference assessment results in VHF band; EUROCONTROL; AMCP/WG-B/WP 8-4; Jan. 2000 [6] A proposal for VDL Mode 2 to DSB-AM interference criteria definition; EUROCONTROL; AMCP/WG-B/WP 8-6; Jan 2000 [7] Some further explanations on EUROCONTROL proposed method to assess frequency planning criteria; EUROCONTROL; AMCP/WG-B/IP 8-2; Jan. 2000 [8] Test Results of the Aviation Data System Innovations LLC (ADSI) VDL Mode 4 Equipment for ADS-B Applications in the Upper VOR Band; Trent A. Skidmore and Aaron A. Wilson; Ohio University Avionics Engineering Center; July 1999 [9] VDL2/ACARS/Voice to AM-DSB Interference, Technical Report, Thomson-CSF Communications, B. Bourcier, Dec. 1999 [10] Minimum Operational Performance Specification for an Airborne VDL Mode 2 Transceiver, EUROCAE Document ED-92; March 2000 [11] Compatibility Between The Sound-Broadcasting Service In The Band Of About 87-108 MHz And The Aeronautical Services Band 108-137 MHz, Rec. ITU-R IS.1009-1 [12] Test Procedures For Measuring Aeronautical Receiver Characteristics Used For Determining Compatibility Between The Sound-Broadcasting Service In The Band Of About 87-108 MHz And The Aeronautical Services In The Band 108-118 MHz, Rec. ITU-R IS.1140 [13] Test procedures and results for the development of frequency planning criteria for VDL Mode4; WP of

1 AMCP-WG-B meeting in San Diego, January 2001.

2 1. Introduction

This report contains test data related to:

 VDL Mode 4 power spectrum measurements  VDL Mode 4 receiver sensitivity  VDL Mode 4 interference on VDL Mode 4  VDL Mode 4 interference on analog voice DSB-AM radios and vice versa This includes also a validation of the so called S/P 6 dB criteria. Comprehensive voice samples have been recorded in that context.  VDL Mode 4 interference on VDL Mode 2  VDL mode 2 interference on VDL Mode 4, but only for –82 dBm input power value. Measurements for –88 dBm input power value are still missing.  VDL Mode 4 interference on VOR  VDL Mode 4 interference on ILS

No data on impact of VDL Mode 4 on GBAS and vice versa could be gathered due to lack of GBAS equipment. As VDL Mode 4 units two radios from one manufacturer have been investigated in detail.

In section 2 a short introduction of the different test cases used is outlined.

In the appendices A to G different test cases are described in more detail.

In appendix I measurement results are outlined. These results cover the grey shaded cases in table 1-1 below.

Table 1-1: Overview on test cases conducted (grey shaded)

Interference Source vs. DSB-AM VDL-2 VDL-3 VDL-4 GBAS VOR ILS FM DSB-AM 1 & 2 1 & 2 1 & 2 - - - - VDL-2 3 3 3 3 - - - - VDL-3 3 3 3 3 - - - - Victim VDL-4 3 3 3 3 3 GBAS - - - 3 - - - - VOR - - - 4 - - - - ILS - - - 5 - - - - FM ------

Note: The number for each test case outlines the used test method as described in appendicies C through G (e.g. „3“ means „ method 3“).

The author would like to thank his colleagues Mr. Günzel (DFS) and Mr. Heinrichs (Consultant) for their support in conducting the measurements. Their expertise allowed to define test cases and helped to significantly expedite the measurement process.

3 2. Overview on test cases

Table 2-1: Overview on test cases to be conducted

Interference Source vs. DSB-AM VDL-2 VDL-3 VDL-4 GBAS VOR ILS FM DSB-AM - 1 & 2 1 & 2 1 & 2 - - - - VDL-2 3 3 3 3 - - - - VDL-3 3 3 3 3 - - - - Victim VDL-4 3 3 3 3 3 GBAS - - - 3 - - - - VOR - - - 4 - - - - ILS - - - 5 - - - - FM ------

Note: The number for each test case outlines the used test method as described in appendicies C through G (e.g. „3“ means „ method 3“).

In a first step before conducting all outlined test conditions, the following measurements have to be made:

- measurement of spectrum - measurement of receiver sensitivity

2.1 Measurement of spectrum

For the purpose of spectra evaluation a Rohde & Schwarz Spectrum Analyser (type: FSIQ 3) has been used. In an earlier WP this issue on how to measure spectrum of a bursted signal has been discussed. Further investigation led to the following parameter settings referred to as option 3 (option 1 and 2 are already described in [13]):

Option 1: Resolution bandwidth: 100 Hz Power measurement: RMS detector (no correction factor needed) Spectra evaluation: Max hold

Option 2: Measurement with zero span in the time domain. Tuning to the appropriate 25 kHz channel and using a gaussian filter with 3 dB bandwidth of 20 kHz (reslution bandwidth). After averaging the data, the maximum value indicated on the screen during burst transmission shall be recorded. This option is not suitable to measure the correct spectrum, but gives a quick overview of the spectrum shape and might be used for comparison between different DUTs (devices under test).

Option 3: Resolution bandwidth: 500 Hz Power measurement: sample detector Spectra evaluation: 30s sweep time

In all cases power measurements have been done within a bandwidth of 25 kHz. Option 1 and 3 showed quite similar results, therefore it could be assumed, that values are correct (s. Appendix I.1). In both cases total power measurements using zero span method like in option 2 for the desired frequency has been used to calibrate.

2.2 Measurement of Receiver Sensitivity

Receiver sensitivity is defined as the minimum signal level at the input of the receiver to provide the nominal uncorrected BER under conditions of no external noise. In case of VDL Mode 4 and SYNC burst transmissions this is equivalent to the minimum signal level at the input of the receiver to produce the nominal uncorrected MER (message error rate) of 2*10E-2.

4 The test setup to evaluate BER or MER is outlined in appendix E explaining test method 3; however, for this test measuring receiver sensitivity the following changes are required:  undesired source powered down;  desired VDR signal level varied as required to calibrate MER curve around the desired operating point;

5 Appendicies:

Appendix A: Definition of interference

Appendix B: Essential Physical Layer parameters to be used within WG B work

Appendix C: Test method 1

Appendix D: Test method 2

Appendix E: Test method 3

Appendix F: Test method 4

Appendix G: Test method 5

Appendix H: Sample link budget for the protection of GNSS

Appendix I: Test Results

6 APPENDIX A DEFINITION OF INTERFERENCE

The definition of harmful interference is defined in RTCA DOC 225 as:- “Interference that endangers the functioning of a radio navigation service or of other safety services, or seriously degrades, obstructs, or repeatedly interrupts a radio communication service operating in accordance with ITU Radio Regulations”

On the basis of this definition it is recommended that the following practical criteria would be used to define the interference limits to be used in the relevant testing:-

DSB-AM either Squelch break or When a wanted signal is degraded sufficiently to be intolerable to the user

VDL Mode 2 When the uncorrected bit error rate exceeds 1 in 10-3 Mode 3 When the uncorrected bit error rate exceeds 1 in 10-3 Mode 4 When the uncorrected bit error rate exceeds 1 in 10-4 Remark: In case of VDL Mode 4 the uncorrected bit error rate of 1 in 10-4 is equivalent to the uncorrected message error rate of 2 in 10-2 for one slot transmissions.

7 APPENDIX B ESSENTIAL PHYSICAL LAYER PARAMETERS TO BE USED WITHIN WG B WORK

DSB-AM

Airborne Transmitter Power output = 44 dBm MOPS Feeder loss = 3 dB Assumed figure (used in RTCA172) Antenna gain = 0 dB Assumed

Receiver Minimum expected signal at the = 75V/m Annex 10 Volume III, Part II, Para antenna  -82dBm (isotropic Antenna) 2.3.2.2.1 Feeder loss = 3 dB Assumed figure (used in RTCA172) Antenna gain = 0 dB Assumed

Ground Transmitter Power output = 50 dBm Annex 10 Volume V, Attachment A, Para 2.4 Feeder loss = 3 dB Assumed figure (used in RTCA172) Antenna gain = 2 dB Assumed

Receiver Minimum expected signal at the = 20V/m Annex 10 Volume III, Part II, Para antenna  -93dBm (isotropic Antenna) 2.2.2.2. Feeder loss = 3 dB Assumed figure (used in RTCA172) Antenna gain = 2 dB Assumed

VDL MODE 2/3

AIRBORNE & GROUND Transmitter Power output = 42 dBm (on channel VDL Mode 2) MOPS 44 dBm (on channel VDL Mode 3) MOPS

-18 dBm (1st Adjacent, 16kHz BW) Annex 10 Volume 3, Part I, Para 6.3.4 -28 dBm (2nd Adjacent, 25kHz BW) Annex 10 Volume 3, Part I, Para 6.3.4 -38 dBm (4th Adjacent, 25kHz BW) Annex 10 Volume 3, Part I, Para 6.3.4 -43 dBm (8th Adjacent, 25kHz BW) Annex 10 Volume 3, Part I, Para 6.3.4 -48 dBm (16th Adjacent, 25kHz BW) Annex 10 Volume 3, Part I, Para 6.3.4 -53 dBm (32nd Adjacent, 25kHz BW) Annex 10 Volume 3, Part I, Para 6.3.4 Feeder loss = 3 dB Assumed figure (used in RTCA 172)

8 Antenna gain = 0 dB (airborne) Assumed 2 dB (ground) Assumed

Receiver Minimum expected = 20V/m Annex 10 Volume 3, Part II, Para signal at the antenna -93dBm (isotropic Antenna) 6.3.5.1 Undesired signal = 40 dB (1st Adjacent channel) rejection 60 dB (3rd Adjacent channel) Feeder loss = 3 dB Assumed figure (used in RTCA 172) Antenna gain = 0 dB (airborne) Assumed 2 dB (ground) Assumed

VDL MODE 4

AIRBORNE & GROUND Transmitter Power output = 40 dBm (airborne at the antenna MOPS VDL Mode 4) 44 dBm (ground at the antenna VDL MOPS Mode 4) -18 dBm (1st Adjacent, 16kHz BW) Annex 10 Volume 3, Part I, Para 6.3.4 -28 dBm (2nd Adjacent, 25kHz BW) Annex 10 Volume 3, Part I, Para 6.3.4 -38 dBm (4th Adjacent, 25kHz BW) Annex 10 Volume 3, Part I, Para 6.3.4 -43 dBm (8th Adjacent, 25kHz BW) Annex 10 Volume 3, Part I, Para 6.3.4 -48 dBm (16th Adjacent, 25kHz BW) Annex 10 Volume 3, Part I, Para 6.3.4 -53 dBm (32nd Adjacent, 25kHz BW) Annex 10 Volume 3, Part I, Para 6.3.4 Feeder loss = 3 dB Assumed figure (used in RTCA 172) Antenna gain = 0 dB (airborne) Assumed 2 dB (ground) Assumed

Receiver Minimum expected = 35V/m Annex 10 Volume 3, Part II, Para signal at the antenna -88dBm (isotropic Antenna) 6.9.5.1.1.1 Undesired signal = 40 dB (1st Adjacent channel) rejection 60 dB (3rd Adjacent channel) Feeder loss = 3 dB Assumed figure (used in RTCA 172) Antenna gain = 0 dB (airborne) Assumed 2 dB (ground) Assumed

9 APPENDIX C TEST METHOD 1

INTRODUCTION

This test method can be used to assess the impact of VDL signals on a DSB-AM (25 kHz and 8,33 kHz) victim receiver and is based on the ratio of power of the desired and undesired signals in the passband of the receiver. This method was used as the basis for the work which lead to a change in the VDL transmitter mask adopted by AMCP 6

SQUELCH BREAK

Test Setup

AM Receiver Under Test

RF Combiner

Variable RF Variable RF Attenuator Attenuator

Desired AM Signal Source Undesired VDR Signal Source

Test Procedure

 The undesired VDR is tuned to the centre frequency of the AM receiver under test and the signal level increased until the squelch is broken and the level recorded.  The undesired VDR is then tuned to the adjacent channel and the signal level increased until the squelch is broken and the level recorded.  The undesired VDR is then tuned to the next adjacent channel in a given set of N adjacent channels and the signal level increased until the squelch is broken and the level recorded. This is repeated until the last channel in the reference set is tested.  AM test frequencies are 119, 128 and 136 MHz.  Adjacent channels be used are 1st, 2nd, 3rd, 4th, 5th, 10th, 20th, 40th (25 kHz spacing) as far as possible.  Desired AM source is turned off.

Remark: This tests are also covered within test method 2 and therefore not required.

10 ON CHANNEL D/U RATIO

Test Setup

Audio Recorder

AM Receiver Under Test

RF Combiner

RF RF Attenuator Attenuator

Desired AM Signal Source Undesired VDR Signal Source

Test Procedure

 The desired AM signal is set so as to produce a –82dBm or –93 dBm, 30% modulated with ATC phrases at the input of the victim receiver Remark: -93 dBm simulates a worst case scenario for a ground receiver.

 The undesired VDL signal is then set to give a W dB D/U in the passband of the receiver on the first and subsequent adjacent channels and a recording made of the audio output from the receiver for each adjacent channel. W is determined by subjective testing for each VDL mode.  A listening panel then assess the quality of the audio results recorded scoring each.

Remark: Tests regarding a –82 dBm value have already been made and results are outlined in Ref. [1] with a recommendation for 20 dB D/U in case of VDL Mode 4.

11 APPENDIX D TEST METHOD 2

INTRODUCTION

This test method investigates separately the effects of the pulse and continuous modulation of a digital signal on a DSM-AM (25 kHz and 8,33 kHz) victim receiver. By separating the effects of the pulse and modulation two objective parameters can be defined which can therefore be tested for and measurements made. To assess the impact of a digital signal on a DSB-AM receiver in the presence of a wanted signal two criteria are proposed a Signal + Noise to Noise ratio (S+N/N) and a signal to pulse (S/P) ratio.

SQUELCH BREAK

Test Setup

AM Receiver Under Test

RF Combiner

RF RF Attenuator Attenuator

Desired AM Signal Source Undesired VDR Signal Source

Test Procedure

 The undesired VDR is tuned to the centre frequency of the AM receiver under test and the signal level increased until the squelch is broken and the level recorded.  The undesired VDR is then tuned to the adjacent channel and the signal level increased until the squelch is broken and the level recorded.  The undesired VDR is then tuned to the next adjacent channel in a given set of N adjacent channels and the signal level increased until the squelch is broken and the level recorded. This is repeated until the last channel in the reference set is tested  AM test frequencies are 119, 128 and 136 MHz.  Adjacent channels be used are 1st, 2nd, 3rd, 4th, 5th, 10th, 20th, 40th (25 kHz spacing) as far as possible.  Impact of short (one slot) and long transmissions from the undesired VDR (VDL Mode 4) for different duty cycles shall be investigated.

Note: The following interference scenarios for VDL Mode 4 shall be considered:

12  1.3 % duty cycle (one Sync burst transmission in one slot every second) simulating worst case cosite scenario  2.7 % duty cycle (two slot burst transmission every second) simulating worst case cosite scenario for transmitting e.g. TCP-information  50 % duty cycle (Sync burst transmissions in every other slot) simulating a medium dense scenario of interferers at equal distance  50 % duty cycle (two slot burst transmissions in every other two slots) simulating a medium dense scenario of interferers at equal distance

 Desired AM source is turned off.

S+N/N RATIO DEGRADATION

Test Setup

Audio Test Equipment

AM Receiver Under Test

RF Combiner

RF RF Attenuator Attenuator

Desired AM Signal Source Undesired VDR Signal Source

Test Procedure

 The wanted signal is set so as to produce a –82 dBm or –93 dBm, 30% modulated 1 kHz tone (30 % modulation depth) at the input of the victim receiver.

Note: Also 90% modulation depth might be investigated due to the fact, that this refers to an average modulation depth of 30% for real speech signals.

 The undesired VDR is set in bursted mode with a centre frequency offset from the desired AM signal by one channel and the level of signal at the input of the victim AM receiver

13 varied until a S+N/N degradation on the audio output of 6 dB is measured and the level noted.

Note 1: The S+N/N measurement is conducted with an output power meter as „audio test equipment“. The S+N values are derived with a desired signal with modulation present, whereas the N value is derived with the modulation removed. In fact the procedure gives the (S+D+N)/N ratio in case additional harmonic distortion D is present.

 When the (S+N)/N ratio reduction of 6 dB is reached, the audio level is measured to check that it is more than the nominal level minus 6 dB. If it were not the case, so the unwanted signal level to get the nominal audio level minus 6 dB would be noted. Note 3: The receiver degradation could also appear to be an audio „blocking“ (audio level reduction). The tolerance generally considered for this audio reduction is 6 dB.

 The audio distortion is then checked to ensure that it is less than 10%, which is equivalent to (S+D)/D or better than 20 dB. If this is not the case then the unwanted VDR signal level required to get a 20 dB (S+D+N/N) value is noted. Note 4: Audio distortion will be measured with a distortiometer as „audio test equipment“. The measurement principle is to reject the audio tone of 1 kHz (modulation signal). The audio fundamental at 1 kHz is suppressed and the remaining energy is due to the audio harmonics, hence to the distortion (in %). However the measurement is correct only if the noise energy is low enough. In fact the measurement gives the (S+D+N)/(D+N) ratio.

 This is repeated for the next adjacent channel for the undesired VDR in a given set of N adjacent channels.  Adjacent channels be used are 1st, 2nd, 3rd, 4th, 5th, 10th, 20th, 40th (25 kHz spacing) as far as possible.  AM test frequencies are 119, 128 and 136 MHz.

14 SIGNAL TO PULSE RATIO LEVEL

Test Setup

Audio Test Equipment

AM Receiver Under Test

RF Combiner

RF RF Attenuator Attenuator

Desired AM Signal Source Undesired VDR Signal Source

Test Procedure

 The wanted signal is set so as to produce a –82dBm or –93 dBm, 30% modulated 1kHz tone (30 % modulation depth) at the input of the victim receiver

Note: Also 90% modulation depth might be investigated due to the fact, that this refers to an average modulation depth of 30% for real speech signals.

 The undesired VDR is set in burst mode with a centre frequency offset from the desired AM signal by one channel and the level of signal at the input of the victim AM receiver varied until level of the audio pulses is 6 dB below the nominal audio peak level (the audio pulse level is half of the nominal audio peak level)  Note: The measurement procedure is as follows; Modulate the wanted signal with a 1 kHz tone. Note the audio peak level (1 kHz) at the receiver audio output with the unwanted transmitter off. Then suppress the wanted signal modulation and increase the unwanted signal level to get spurious audio pulses half of the nominal audio peak level, which means that S/P is now equal to 6 dB.

 The undesired VDR is then set to the next adjacent channel and the level of signal at the input of the victim AM receiver varied until the audio pulse level is 6 dB below the nominal audio peak level and the level noted.  This is repeated for the next channel in a given set of N adjacent channels.  AM test frequencies are 119, 128 and 136 MHz.

15  Adjacent channels be used are 1st, 2nd, 3rd, 4th, 5th, 10th, 20th, 40th (25 kHz spacing) as far as possible. APPENDIX E TEST METHOD 3

INTRODUCTION

This test method can be used to assess the impact of either a DSB-AM or VDL signal on a VDL victim receiver and is based on the bit error rate performance of the radio

Note: In case of VDL Mode 4 as an alternative the evaluation of message error rate performance is proposed.

BIT ERROR RATE TEST

Test Setup

VDR Receiver Under Test

RF Combiner

Variable RF Variable RF Attenuator Attenuator

Desired VDR Signal Source Undesired AM/VDR Signal Source

Test Procedure

 The desired VDR signal is set such that the level at the input to the VDR receiver under test is –82dBm or –93 dBm.  The undesired signal source is tuned to the centre frequency of the VDR receiver under test and the signal level increased until the bit error rate of the desired signal falls below the required level and the undesired signal level at the input to the victim receiver recorded.  The undesired signal source is then tuned to the adjacent channel and the signal level increased until the bit error rate of the desired signal falls below the required level and the undesired signal level at the input to the victim receiver recorded.  The undesired signal source is then tuned to the next adjacent channel in a given set of N adjacent channels and the signal level increased until the bit error rate of the desired signal

16 falls below the required level and the undesired signal level at the input to the victim receiver recorded. This is repeated until the last channel in the reference set is tested.  Desired source test frequencies are 119, 128 and 136 MHz.  Adjacent channels be used are 0th (co-channel), 1st, 2nd, 3rd, 4th, 5th, 10th, 20th, 40th (25 kHz spacing) as far as possible.

APPENDIX F TEST METHOD 4

INTRODUCTION

This test method can be used to assess the impact of a VDL Mode 4 signal on a VOR victim receiver and is based on the changes in selected VOR bearing or VOR flag indication.

VOR BEARING CHANGE TEST

17 Test Setup

VDL Mode 4 Source Control and Data Generator

VDL Mode 4 Transmitter VOR Signal Generator

30 dB High Variable Power Attenuator Attenuator

High Isolation Combiner  20 dB Coupler Spectrum Analyser or Power Meter 20 dB Fixed Attenuator

VOR Receiver Under Test

VOR Bearing VOR FLag Output

Test Procedure

 Channel spacing for VOR equipment is 50 kHz.  VDL interference source shall be channelled in 25 kHz steps.  For VDL Mode 4 the following duty cycles shall be investigated:  1.3 % duty cycle (one Sync burst transmission in one slot every second) simulating worst case co-site scenario  2.7 % duty cycle (two slot burst transmission every second) simulating worst case co-site scenario for transmitting e.g. TCP-information  50 % duty cycle (Sync burst transmissions in every other slot) simulating a medium dense scenario of interferers at equal distance  50 % duty cycle (two slot burst transmissions in every other two slots) simulating a medium dense scenario of interferers at equal distance

18 Note: 50 % duty cycle leads to a beat frequency of 37 Hz. VORs are rather sensitive against low beat frequencies on the order of 30 Hz. This scenario could be considered as a medium dense scenario with interferers at equal distance.

 VOR test frequencies are fVOR,i = 112 MHz, or 115 MHz, or 117.95 MHz.  Both co- and adjacent channel interference shall be investigated using the following

VDL frequencies: fVDL,i = fVOR,i  25 (,or 50, or 75, or 100) kHz  Interference criteria shall be the changes in selected VOR bearing of  0,3° (Rec. ITU- R IS.1140) or appearance of flag, which ever comes first.

Note: A 0.3° course indicator deflection equates to a deviation bar drive current of 4.5 µA.

 For each series of tests the output power level on the VOR Signal Generator will be set to provide –79 dBm RF input level (ICAO and RTCA/DO-196 reference signal level) at the VOR receiver under test.

19 APPENDIX G TEST METHOD 5

INTRODUCTION

This test method can be used to assess the impact of a VDL Mode 4 signal on a ILS victim receiver and is based on ITU-R IS.1140 [12] recommendations.

Test Setup

Test setup is equal to test method 5, but with ILS Signal Generator and ILS Receiver under test.

Test Procedure

 VDL interference source shall be channelled in 25 kHz steps.  For VDL Mode 4 the following duty cycles shall be investigated:  1.3 % duty cycle (one Sync burst transmission in one slot every second) simulating worst case co-site scenario  2.7 % duty cycle (two slot burst transmission every second) simulating worst case co-site scenario for transmitting e.g. TCP-information  50 % duty cycle (Sync burst transmissions in every other slot) simulating a medium dense scenario of interferers at equal distance  50 % duty cycle (two slot burst transmissions in every other two slots) simulating a medium dense scenario of interferers at equal distance

 ILS test frequency is fVOR,i = 111.95 MHz.  Both co- and adjacent channel interference shall be investigated using the following

VDL frequencies: fVDL,i = fVOR,i  25 (,or 50, or 75, or 100) kHz

The interference thresholds for a wanted signal with a difference in depth of modulation (DDM) of 0.093 are:

 a change in course deflection current of 4,5 A, or  the appearance of the flag, whichever occurs first  For each series of tests the output power level on the ILS Signal Generator will be set to provide –86 dBm RF input level (ICAO and RTCA/DO-195 reference signal level) at the ILS receiver under test.

20 APPENDIX H SAMPLE LINK BUDGET FOR THE PROTECTION OF GNSS

Sample link budget for the protection of GNSS receivers on board the same aircraft as a VDL transceiver GPS Interference Threshold (dBm) -110.5 Expected Antenna Isolation (dB) -30* GPS antenna gain, dBi -4.5 Reqd VDL Spurious and Harmonic -76** Emission Limit, eirp (dBm) * Antenna isolations will vary from airframe to airframe. ** One administration is planning to require that newly certified VHF A/G radios control their spurious emissions and harmonics in the GNSS (L1) frequency band (1559-1610 MHz) to an eirp of –80 dBm.