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4) reflection coefficient of unity magnitude;
5) standard atmosphere with a 301 surface refractivity;
6) continental temperate climate;
7) Nakagami-Rice statistics for within-the-horizon fading;
8) an effective radiated power (ERP) corresponding to 1 kilowatt
input power into a lossless half-wave dipole.
ATT A-9
Annex I 0 - Aeronautical Telecommunications Volume V
ill
I S Y
1/11/01 ATT A-10
Attachmenl A Annex 10 - Aeronautical Telecommunications
ATT A-11
Annex I 0 - Aeronautical Telecommunications Volume V
1/11/01 ATT A-12
Attachment A Annex 10 - Aeronautical Telecommunications
ATT A-13
Annex I0 - Aeronautical Telecommunications Volume V
( u l ~ dL. ' 131 8 ~H)13 N3tllS-a1314
ATT A-14
Attachment A Annex 10 - Aeronautical Telecommunications
(WA tf L 'lad BP) H13N3tllS-al31d
ATT A-15
Annex 10 - Aeronautical Telecommunications Volume V
111 1/01 ATT A-16
Attachment A Annex 10 - Aeronautical Telecommunications
ATT A-17
ATTACHMENT B. CONSIDERATIONS AFFECTING
THE DEPLOYMENT OF LFMF FREQUENCIES AND
THE AVOIDANCE OF HARMFUL INTERFERENCE
1. Particularly in areas of high density of NDBs, it is
recognized that efficient planning is essential in order to: a)
ensure satisfactory operation of ADF equipment, and b)
provide the most efficient usage of the limited frequency
spectrum available for the NDB service. It is axiomatic that
regional meetings will so plan facilities as to ensure that all
facilities will receive the best possible protection from harmful
interference. Nevertheless, in certain regions, congestion of
facilities has been such that regional meetings have had to plan
in terms of a minimum protection ratio.
Regional meetings include in their planning consideration
of such factors as:
a) the possibility of reducing the number of NDBs
required, by coordination of system plans;
b) the possibility of reducing the coverage where a lesser
grade of service than that obtainable within the rated
coverage is acceptable;
c) the characteristics of ADF equipment in use;
d) the atmospheric noise grades, appropriate to the area
concerned;
e) ground conductivity; and
f) interference protection required at the edge of the rated
coverage.
Of the foregoing factors, that which is most susceptible to
improvement of a technical kind is c).
2. The 1979 World Administrative Radio Conference
adopted regulations concerning the assignment of frequencies
for aeronautical radio beacons operating in the LFIMF
frequency bands. A minimum protection ratio (wanted1
unwanted signal ratio) of 15 dB is to be used as the basis for
frequency assignment planning (RR Appendix S12). The
following data concerning the attenuation characteristics of
ADF equipment was used in the EUR region to aid in the
frequency assignment process:
Frequency A ttenuntion
difference (kHz) (dB)
The above figures (or distance separation criteria derived
from them) have also been applied in other regions in
determining the minimum protection ratio.
Where a bearing accuracy of k5 degrees is required at the
edge of cover, a minimum protection of 15 dB by day should
be used as the basis for LFIMF channel assignment planning.
3. In view of the fact that in many regions there is a need
to improve the planning criteria it is considered that the main
source from which improvement can be derived is recognition
of higher attenuation figures than those given above. Regional
meetings are accordingly advised that, when the congestion is
such that the use of the above figures no longer permits
efficient planning of the LFIMF frequency spectrum available,
the following figures represent from a technical point of view
the best that can be accepted in determining distance
separation criteria:
Frequency Attenuation
diflerence (kHz) (dB)
When using these figures, it should be noted that the RF
selectivity of modem ADF equipment is in general better
ANNEX 10 - VOLUME V ATT B-1
Annex 10 - Aeronautical Telecommunications
than these figures and that, while the RF selectivity of older
ADF equipment is not better than these figures, consideration
of the dynamic characteristic of this older equipment shows
this to be better. It could therefore be expected that frequency
planning based on the new figures would considerably
improve the service provided to users of modem equipment,
and would not materially reduce the service presently provided
to those aircraft using the older equipment.
Volume V
Nevertheless, in their planning, regional meetings would
　
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