CHAPTER 1

Aeronautical radionavigation service

1.1 Separation distance for compatibility

Table 5.1 gives the minimum separation distances between a test point of the radionavigation station to be protected and a sound broadcasting station at which the protection criteria for Al, A2, B1 and B2 types of interference are all met. The more critical requirements are those for Al and Bl; the higher of the two separation distances is shown in each case.

The Al distances assume the protection ratio for frequency coincidence, and that the level of the broadcasting transmitter spurious emissions conform to the level given in section 7.6.3.2 of Annex 2. The B1 distances ensure that the signal level is below the cut-off value as given in section 7.6.5.4 of Annex 2 with free-space propagation, but are subject to an upper limit of 500 km due to the practical considerations of the line-of-sight limit, in conformity with section 7.3 of Annex 2.

Where two or more assignments are used at a common site, the highest e.r.p. must be taken.

Linear interpolation shall be used for e.r.p. (in dBW) and frequency values not appearing in the table.

Preliminary analyses based on these distances assume, in the case of A1 and B1 types of interference, that there is frequency coincidence between a spurious emission or intermodulation product and the frequency of the radionavigation station. When the frequencies of the radionavigation station and of all broadcasting transmitters that may be involved are known, detailed calculations can be made for all types of interference using the data for protection of the aeronautical radionavigation service given in Chapter 7 of Annex 2. However, in the case of A1 type interference it will be necessary to check that the transmitter does not generate significant spurious components apart from third-order intermodulation products.

Any case-by-case study may take into account other relevant factors such as details of the propagation path between the broadcasting station and the aeronautical test point, and the radiation pattern of the broadcasting antenna in both the vertical and horizontal planes.

1.2 Future improvements in aeronautical receivers

It is expected that future receivers will permit a significant relaxation of compatibility criteria and that the following revised criteria will be applied from 1 January 1998.

1.2.1 B1 type interference

Present indications from the ICAO are that the two-signal case criterion for B1 type interference given in section 7.6.5.1 of Annex 2 will be replaced by:

for both ILS and VOR receivers.

TABLE 5.1

Minimum separation distance in km between a test point of a radionavigation station and a sound broadcasting station required to ensure compatibility

Broadcasting station frequency (MHz)

Effective radiated power of broadcasting station | < 100 | 102 | 104 | 106 | 107 | 107.7 to 107.9

dBW | W | Separation distance (km)

55 | 300k | 40 | 53 | 99 | 245 | 500 | 500

50 | l00k | 22 | 31 | 57 | 141 | 302 | 500

45 | 30k | 20 | 20 | 31 | 77 | 166 | 494

40 | 10k | 20 | 20 | 20 | 45 | 96 | 285

35 | 3k | 20 | 20 | 20 | 24 | 52 | 156

30 | 1k | 20 | 20 | 20 | 20 | 30 | 90

25 | 300 | 20 | 20 | 20 | 20 | 20 | 49

20 | 100 | 20 | 20 | 20 | 20 | 20 | 29

<I5 | 30 | 20 | 20 | 20 | 20 | 20 | 20

Subject to further study of type B1 interference by the CCIR, it is expected that a comparable relaxation in the criterion for the three-signal case will be possible and that the trigger and cut-off values given in section 7.6.5.2 of Annex 2 will be raised by 16 dB.

1.2.2 B2 type interference

The maximum permitted broadcasting signal levels at the input to the ILS or VOR receiver for B2 type interference shall be those given in the Table 5.2 in place of the values given in Table 2.11 of Annex 2.

TABLE 5.2

Frequency of broadcasting signal (MHz) | Level (dBm)

107.9 106 102 ≤ 100 | -10 5 15 15

For frequencies in between the values given above, the maximum permitted level will be determined by linear interpolation.

1.2.3 Further studies

Studies on possible improvements are requested in Recommendation No. 4.

CHAPTER 2

Fixed and mobile services, except the aeronautical mobile (OR) service

2.1 Sharing criteria for the protection of the land mobile service in the bands 87.5-100 MHz and 104-108 MHz

Field strength to be protected: | 15 dB (μV/m) at a height of 3 m

Protection ratio: | See Table 5.3

TABLE 5.3

Frequency separation between carriers of the two services (kHz) | Protection ratio for the AM land mobile service (dB) | Protection ratio for the FM land mobile service (dB)

0 25 50 75 100 | 18 16 4.5 -7.5 -17.5 | 8 6 -5.5 -17.5 -27.5

Propagation data to be used for sharing calculations:

Propagation curves for calculating interference to the land mobile service operating in the VHF bands shall be derived from the broadcasting propagation curves (Figures 4.1, 4.2 and 4.3 of Annex 4). Since these propagation curves are for a receiving antenna height of 10 m above the local terrain and the receiving antenna height is reduced from 10 m to 3 m, a 9dB reduction in the field strength shall be applied.

Note - The method and criteria concerning antenna height gain factors to be used by administrations for coordination between the broadcasting and land mobile and fixed services are to be agreed by the administrations concerned and should be based where possible on the latest relevant CCIR Recommendations.

Percentage of location to be protected: | 50%

Percentage of time to be protected: | 90%

Polarization discrimination for horizontally polarized broadcasting emission: 18 dB base station

2.2 Sharing criteria between FM sound broadcasting and the fixed service in the band 87.5-100 MHz and 104-108 MHz

The basic criteria can be those established for a base station in the land mobile service (see section 2.1 in this Annex). The field strength to be protected the height gain factors other than those specified and the effect of the directivity of the antenna in the fixed service will be considered by the administration concerned.

CHAPTER 3

Aeronautical mobile (OR) service

When the frequencies of the broadcasting and the aeronautical mobile stations are both known, the field strengths given in Table 5.4 below may be used as sharing criteria.

TABLE 5.4

Frequency separation in kHz between broadcasting station and aeronautical mobile (OR) station | Field strength in dB(μV/m) at an altitude of 10 000 metres

0 50 100 150 | 20 34 58 90

CHAPTER 4

Supplementary propagation data correction factors

This chapter gives supplementary correction factors which can be applied to the basic propagation curves to improve the accuracy of predictions in particular cases of coordination involving bilateral or multilateral negotiations between administrations.

4.1 Correction for various location percentages

The propagation curves in Annexes 2 and 5 are representative of 50% of locations. Figure 5.1 shows the correction (in dB) to be applied for other percentages of receiving locations.

4.2 Receiver terrain correction (terrain clearance angle)

The location correction in section 4.1 above can be applied only on a statistical basis. If more precision is required for predicting the field strength in a specific small receiving area a correction may be based on a "terrain clearance angle". This angle Θ is measured at a point chosen to be representative of the reception area; it is defined as the angle between the horizontal plane passing through the receiving antenna and the line from this antenna which clears all obstacles within 16 km in the direction of the transmitter. The example in Figure 5.2 indicates the sign convention, which is negative if the line to the obstacles is above the horizontal. Figure 5.3 indicates the correction, as a function of the angle 9, to be applied to the prediction for 50% of locations. If this correction is applied, the location correction in section 4.1 (Figure 5.1) may no longer be applicable.