SPECIFICS ON FM BROADCAST
INTERFERENCE
presentation by
Steve Mitchell, UK
ICAO Regional Spectrum
Seminar, Cairo, Egypt June 2006
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A LITTLE BIT OF HISTORY
 Changes to ITU Radio Regulations
recognition of potential interference to
aeronautical systems
studies within the ITU
initial studies
further enhanced studies
final ITU recommendations
ICAO Regional Spectrum
Seminar, Cairo, Egypt June 2006
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GENERAL TYPES OF INTERFERENCE
 Four types of interference to consider
Type A
A1
A2
Type B
B1
2 signal
3signal
B2
ICAO Regional Spectrum
Seminar, Cairo, Egypt June 2006
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DIFFICULTIES WITH ILS/VOR/COM
Extensive testing
ILS/VOR receivers
3rd order intermodulation
saturation
Com receivers
ICAO Annex 10 SARPs requirements
3rd order 2 signal
Desensitisation
ICAO Regional Spectrum
Seminar, Cairo, Egypt June 2006
n
DIFFICULTIES WITH GBAS
AND VDL 4
 Testing of GBAS and VDL 4 receivers
same mechanisms apply as for ILS/VOR/COM
avionics manufacturers tests above 112 MHz
split in desensitisation requirements
similar A1and B1 criteria as ILS/VOR
 ICAO Annex 10 SARPs requirements
3rd order 2 signal
Desensitisation
ICAO Regional Spectrum
Seminar, Cairo, Egypt June 2006
n
Co-ordination
 Why co-ordination?
Between FM broadcasters
mutual sharing
Between FM broadcasters and aeronautical
avoid interference to aeronautical services
Between aeronautical and FM broadcasters
avoid potential problems
ICAO Regional Spectrum
Seminar, Cairo, Egypt June 2006
n
Example of co-ordination process
Example of an approach to coordination
European example
inside a State
databases
computer tools
agreement mechanism
between States
LEGBAC/EBU
ICAO Regional Spectrum
Seminar, Cairo, Egypt June 2006
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TYPE A1 CALCULATION
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TYPE A2 CALCULATION
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TYPE B1 CALCULATION
2 SIGNAL
ICAO Regional Spectrum
Seminar, Cairo, Egypt June 2006
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TYPE B1 CALCULATION
3 SIGNAL
b)
Three-signal case
N1 – 20 log
max (0. 4; 108. 1 – f1)

0. 4
N2 – 20 log
max (0. 4; 108. 1 – f2)

0. 4
N3 – 20 log
max (0. 4; 108. 1 – f3)
 K  6 – Lc  S  0
0. 4
where:
f1, f2, f3 :
broadcasting frequencies (MHz) f1  f2,  f3
N1, N2, N3 : broadcasting signal levels (dBm) at the input to the aeronautical receiver for broadcasting
frequencies f1, f2 and f3 respectively
K 
78 for ILS localizer and VOR
Lc :
correction factor (dB) to account for changes in wanted signals, (see § 4.3.3.3)
S : 3 dB margin to take into account of the fact that the ICAO Annex 10 1998 receiver immunity
criteria equations do not provide comprehensive compatibility assessment formulae.
ICAO Regional Spectrum
Seminar, Cairo, Egypt June 2006
(11)
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TYPE B2 CALCULATION
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Seminar, Cairo, Egypt June 2006
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TRIGGER AND CUT-OFF CALCULATIONS
ICAO Regional Spectrum
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ILS PROTECTION
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Seminar, Cairo, Egypt June 2006
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VOR PROTECTION
ICAO Regional Spectrum
Seminar, Cairo, Egypt June 2006
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PRACTICAL SOLUTIONS
WITH AUDIENCE PARTICIPATION
ICAO Regional Spectrum
Seminar, Cairo, Egypt June 2006