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used to calculate both the free-space loss of the desired signal and other system characteristics
(FSLD) and the free-space loss of the undesired signal (FSLU):
FSL (in dB) = 32.4 + 20 log f + 20 log d
where f = frequency in MHz
d = distance in km.
2.1 For aircraft receivers designed for operation in a
50 kHz channel spacing environment and a ground station
frequency tolerance of 50 parts in lo6 (+0.005 per cent), an
effective adjacent channel rejection characteristic of 60 dB or
better is assumed. This assumotion will result in a
geographical separation distance between the nearest limits of
In com~aringth e FSLD versus the F"U, the subtraction of the the functional service ranges of the two facilities of at least
formula results in: 5.6 km (3 NM).
FSLu - FSLD = 20 log dU - 20 log dD
= 20 log dU/dD
If FSL, - FSLD = 14 dB,
then log dU/dD = 14/20 = 0.7;
then dU/dD = 5.01.
2.2 For aircraft receivers designed for operation in a
25 kHz channel spacing environment and a ground station
frequency tolerance of 20.002 per cent, and for aircraft
receivers designed for operation in a 8.33 kHz spacing
environment, and a ground station frequency tolerance of
+.0001 per cent, an effective adjacent channel rejection
ANNEX 10 - VOLUME V ATT A-1 1111N)l
Annex 10 - Aeronautical Telecommunications Volume V
Radio horizon 1
Figure A-1. Geographical separation required for
co-channel operation of VHF facilities
4. Azimuth preferably limited
to 3 dB above a dipole
I. Determine line of sight
2. Determine azimuth angle 0
3. Measure off 2 times azimuth angle (C-D and C-E)
4. Determine azimuth, preferably limited to 3 dB above a dipole (D-E)
Figure A-2. Limit of azimuth protection for VHF facilities which
provide a sewice beyond the radio horizon
ATT A-2
Attachment A Annex 10 - Aeronautical Telecommunications
Subject aircraft at protected
height and range of desired DOC
Service ranae of the 1
Service range of the
desired facility
Figure A-3. Co-channel configuration for
undesiredldesired distance ratio
characteristic of 60 dB or better is assumed. This assumption
will result in a geographical separation distance between the
nearest limits of the functional service ranges between two
facilities using 25 kHz spacing or between two facilities using
8.33 kHz spacing of at least 5.6 km (3 NM).
2.3 The above criteria are based on the concept of
protection by receiver muting, except in the case of area
control and FIR channels where a minimum field strength is
specified in order to secure the desired wanted-to-unwanted
signal ratio.
2.4 The following additional assumptions were made in
establishing the criteria:
1 ) Propagation: free space propagation between aircraft.
The ITU-R curves for 100 MHz vertical polarization
over land in conjunction with an assumed ground
antenna height of 20 m (65 ft) were used in computing
ground-air field strengths.
2) Minimum jeld strength at limit of functional service
range: 45 dB above 1 microvolt per metre at 3 000 m
(10 000 ft) in the case of area control and FIR
channels.
Note.- To meet this requirement, a station radiating
100 W from an antenna 20 m (65ft) high should be not
more than 185 km (100 NM) from the limit of its
functional service range.
3) Effective radiated power (ERP): a maximum ERP of
20 W from ground and airborne stations with the
exception that, in case of ground stations providing
flight information or area control service communications,
it was necessary to assume a minimum ERP of
100 w.
4) Airborne antenna polar patterns: total variations not
exceeding 10 dB. Since a maximum ERP was assumed
(and therefore all variations are downwards from this
figure), no allowance was necessary in respect of
airborne transmitter polar diagrams.
5) Wanted-to-unwanted signal ratio: 20 dB at the receiver
output.
6) Receiver muting characteristics: a muting threshold
corresponding to a received field strength of 5 microvolts
per metre.
2.5 The following criteria were based on all relevant
assumptions made in 2.4. Two cases related to adjacent
channel interference are considered separately:
a) receiver mute lift; and
b) desired-to-undesired signal ratio.
These cases might cause different planning criteria to be
observed.
ATT A-3
Annex 10 - Aeronautical Telecommunications Volume V
2.5.1 Where it is necessary to take account on a regional
basis of receivers not specifically designed for an 8.33 kHz
environment, the following characteristics should be
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