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its effects.
This chapter deals with Standards and Recommended
Practices relating to this band and includes matters pertaining
to the selection of particular frequencies for various aeronautical
purposes. These Standards are introduced by the
following preface, which sets out the principles upon which the
utilization of VHF on a worldwide basis with due regard to
economy has been planned.
Preface
The utilization of VHF on a worldwide basis with due regard
to economy and practicabiliiy requires a plan that will take
into account:
a) the need for an orderly evolution towards improved
operation and the required degree of worldwide
standardization:
b) the desirability of providing for an economic transition
from present rctilization to optimum utilization of
the frequencies available, taking into account the
maximum possible utilization of existing equipment;
c) the need to provide for coordination between international
and national utilization so as to ensure mutual
protection from intelference;
d) the need for providing a framework for the integrated
development of Regional Plans:
e) the desirability of incorporating in any group of
frequencies to be used those now in use for international
air services;
f) the need for keeping the total number of frequencies and
their grouping in appropriate relation to the airborne
equipment known to be widely used by international air
services;
g) a requirement for the provision of a single frequency
that may be used for emergency purposes on a worldwide
basis and, also, in certain regions, for another
frequency that may be used as a common frequency for
special purposes; and
h) the need for providing suflcient flexibility to allow for
the dtrerences in application necessitated by regional
conditions.
4.1.1 General allotment of
frequency band 117.975 - 137 MHz
Note.- The plan includes a general Allotment Table that
subdivides the complete band 117.975 - 137 MHz, the chief
subdivisions being the bands of frequencies allocated to both
national and international services, and the bands allocated to
national services. Observance of this general subdivision
should keep to a minimum the problem of coordinating
national and international application.
4.1.1.1 The block allotment of the frequency band
117.975 - 137 MHz shall be as shown in Table 4-1.
4.1.1.2 Recommendation, In the case of the band
136 - 137 MHz, international applications have not yet been
agreed, and these frequencies should be brought into use on a
regional basis where and in the manner required.
ANNEX 10 - VOLUME V 4-1 111 1/01
Annex 10 - Aeronautical Telecommunications Volume V
4.1.2 Frequency separation and limits
of assignable frequencies
designed spec$ically for 100 kHz, 50 kHz or 25 kHz channel
spacing will remain adequate for services operating within
such regions or areas. It is further recognized that assignments
based on 25 kHz channel spacing as well as 8.33 kHz
channel spacing may continue to co-exist within one region or
area.
Note.- In the following text the channel spacing for
8.33 kHz channel assignments is defined as 25 kHz divided by
3 which is 8.333 ... kHz.
4.1.2.1 The minimum separation between assignable 4.1.2.2 Until at least 1 January 2005, DSB-AM
equipment specifically designed for 25 kHz channel spacing
shall be safeguarded with respect to its suitability for the
aeronautical mozbile (R) service (AM(R)S) except in those
regions or areas where regional agreement permits the use of
equipment specifically designed for 8.33 kHz channel spacing
or for VDL Mode 3 when used for air-ground voice
communications.
frequencies in the aeronautical mobile (R) service shall be
8.33 kHz.
Note.- It is recognized that in some regions or areas,
100 kHz, 50 kHz or 25 kHz channel spacing provides an
adequate number of frequencies suitably related to international
and national air services and that equipment
Table 4-1. Allotment table
Worldwide utrlizarion Remarks
Block allormenr of
frequencies (MHz)
a) 118 - 121.4
inclusive
International and National
Aeronautical Mobile Services
Specific international allotments will be determined in the light of regional
agreement. National assignments are covered by the provisions in 4.1 S.9.
Emergency frequency In order to provide a guard band for the protection of the aeronautical emergency
frequency, the nearest assignable frequencies on either side of 121.5 MHz are
121.4 MHz and 121.6 MHz, except that by regional agreement it may be decided
that the nearest assignable frequencies are 121.3 MHz and 121.7 MHz.
　
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