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interference to other stations, be kept to the minimum
consistent with the operational requirement for the function.
Annex 10 - Aeronautical Telecommunications Volume V
4.1.5.1 1 Recommendation.- For ground VHF facilities
which provide service beyond the radio horizon, any
spurious or harmonic radiation outside the band +250 kHz
from the assigned carrier frequency should not exceed an
effective radiated power of I mW in any azimuth.
4.1.6 Equipment requirements
Note I.- Frequency tolerances to which stations operating
in the aeronautical mobile band (117.975 - 137 MHz) must
conform are contained in Appendix 3 to the Radio Regulations.
Tolerances for transmitters used for aeronautical services are
not mentioned in this Annex, except in those cases where
tighter tolerances than those contained in the Radio
Regulations are required (e.g. the equipment spec@cations in
Volume I11 contain several such instances).
Note 2.- The frequency tolerance applicable to individual
components of a multi-carrier or similar system will be
determined by the characteristics of the specijic system.
4.1.6.1 Recommendation.- The antenna gain of an
extended range VHF facility should preferably be such as to
ensure that, beyond the limits of +2 about the centre line of
the angular width of the area to be served, it does not
exceed 3 dB above that of a dipole. But, in any case, it should
be such as to ensure freedom from harmful interference with
other radio services.
Note 1.- The actual azimuth, the angular width of the
service area, and the effective radiated power would have to
be taken into account in each individual case.
Note 2.- Guidance material on the interpretation of 4.1.6.1
is contained in Attachment A.
4.1.7 Method of operation
4.1.7.1 Single channel simplex operation shall be used in
the VHF band 117.975 - 137 MHz at all stations providing for
aircraft engaged in international air navigation.
4.1.7.2 In addition to the above, the ground-to-air voice
channel associated with an ICAO standard radio navigational
aid may be used, subject to regional agreement, for broadcast
or communication purposes or both.
4.1.8 Plan of assignable VHF radio frequencies
for use in the international aeronautical
mobile service
Introduction
This plan designates the list of frequencies available for
assignment, together with provision for the use by the
aeronautical mobile (R) service of all frequencies with a
channel spacing of 25 kHz, and of all frequencies with a I
channel width and spacing of8.33 kHz, with the frequencies in
Group A continuing to be used wherever they provide a
suficient number to meet the operational requirements.
The plan provides that the total number of frequencies
required in any region would be determined regionally. The
effect of this will be that frequencies assignable in any
particular region m y be restricted to a limited number of the
frequencies in the list, the actual number being selected as
outlined herein.
In order that the assignable frequencies may be coordinated
between regions as far as practicable, the plan requires that,
whenever the number of frequencies contained in Group A of
4.1.8.1.2 is suficient to meet the requirements of a region, the
frequencies of this Group be used in a sequence commencing
with 118 MHz. This ensures that all regions will have in
common the frequencies used in the region requiring the least
number of frequencies and, in respect to any two regions, the
region with the greater number will have in use all the
frequencies used by the other:
Group A provides for frequency planning based on 100 kHz
channel spacing.
Group B of the list at 4.1.8.1.2 contains the frequencies in
the band 11 7.975 - 132 MHz ending in 50 kHz. Together with
the frequencies in Group A, they provide for frequency
planning based on 50 kHz channel spacing. In Group C are
listed the frequency channels in the band 132 - 137 MHz
based upon 50 kHz channel spacing. Group D contains the
frequency channels in the band 132 - 137 MHz ending in
25 kHz, and Group E similarly lists the frequency channels in
the band 117.975 - 132 MHz. The utilization of channels in
Groups B, C, D and E is explained below.
Group F of the list at 4.1.8.1.2 contains the frequencies in the
band 117,975 - 137 MHz when 8.33 kHz channel width is used.
The utilization of the channels in this Group is explained below.
Whenever the number of frequencies required in a particular
region exceeds the number in Group A, frequencies
may be selected from the other Groups taking into account
　
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