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Coding guidelines
VHF communication (25 KHZ versus 8.33 KHZ spacing)
As explained in the Eurocontrol "8.33kHz Voice Channel Spacing (VCS) Implementation Handbook", edition 1.1, July 2017: "The introduction of 8.33 kHz channel spacing involves the conversion of existing 25 kHz channels to 8.33 kHz channels. An 8.33 kHz channel has a reduced bandwidth compared to its 25 kHz counterpart. This allows for the creation of two adjacent 8.33 kHz channels on the so-called “shoulder” frequencies". The following diagram provides an example:
AIXM allows distinguishing between transmission/reception radio frequencies and radio channels, as explained below:
When 25 KHZ spacing is used, then the frequencyTransmission and the frequencyReception attributes shall be used, both with the same value and including the unit of measurement (MHZ). In addition, the mode attribute shall get the value 'VHF' (which is defined as “Very High Frequency radio voice channel with 25 KHz spacing.”). For example:
- mode='VHF'
- frequencyTransmission=132.050 MHZ
- frequencyReception=132.050 MHZ
When 8.33 KHZ spacing is used, then the channel property shall be used. In addition, the mode attribute shall get the value 'VHF_833' (which is defined as “Very High Frequency radio voice channel with 8.33 KHz spacing.”). For example:
- mode='VHF_833'
- channel=132.055
Frequency purpose (rank)
The rank attribute should be coded in accordance with the usage not with local terminology. For the usage of the values provided for the rank attribute the following rules should be taking into account:
| CodeFacilityRankingType | Rule | |||||
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| PRIMARY | Use for main/normal frequency | |||||
| SECONDARY | Use for secondary frequency and also if other terms (stand-by freq, back-up freq, alternate freq) are used in the sense of a secondary frequency
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| EMERG | Use for emergency frequency, e.g. 121.500 MHZ (Aeronautical emergency frequency), 123.100 MHZ (Auxiliary frequency (SAR)) | |||||
| GUARD | Use if used in the sense of "listening only" frequency, except for emergency frequencies | |||||
| ALTERNATE |
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Annex 10, Volume V, Chapter 4 ,contain a general allotment of the frequency band 117.975 – 137 MHz. The main subdivisions of this band are the frequency bands allocated to both international and national services and frequency bands solely allocated to national services. Specific allotments to services are to be determined regionally. The figure below shows the special frequencies and allotments (Annex 10)
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Note that in the European Region, EUR Doc 011, EUR FREQUENCY MANAGEMENT MANUAL extends the range of frequencies reserved for data link, starting from 136.500 MHz. |
Traffic advisory frequency
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