1. The Air-ground VHF Communication System of Japan
Teruaki Nagasawa
Mobile Satellite Communication Division
Telecommunications Bureau
Ministry of Internal Affairs and Communications, JAPAN
21st -30th March 2012

2. ＜The 25kHz separation system＞ ＜The 8.33kHz separation system＞
１　Introduction
The air-ground VHF communication system (without the VDL system) of Japan is currently using only the 25kHz channel separation system.
However, we are going to revise the Japanese technical scheme on the basis of ICAO ANNEX 10 and RTCA, because Japanese frequencies are very tight. The overview is as follows.
＜The 25kHz separation system＞
＜The 8.33kHz separation system＞
25kHz
25kHz
Channel separation
Channel separation
8.33kHz
Channel separation
6kHz
5.6kHz
Band-width
Band-width
2　Overview
- Channel separation: 25kHz and 8.33kHz
- Quality: Refer to the ICAO SARPs and the RTCA/DO-186 (including 186a and 186b).
- Target: Company radio, Life saving, etc.
- ATC is not included.
3　Schedule
The Ministry of Internal Affairs and Communications of Japan is considering the technical requirement until March 2012.
Thereafter, we are going to make the technical scheme, no later than Summer 2012. ２

3. The Proposal of Technical Requirement (Only 8.33kHz system)
The technical requirement of the air-ground VHF communication system (8.33kHz only) is as follows.
(The requirement of aeronautical stations refers to the ICAO SARPs (ANNEX10), and that of aircraft stations refers to the RTCA DO-186a/b.)
【General Requirements】
Item
Contents
１．Frequency band
ＶＨＦ band
２．Designation of Emission
Ａ３Ｅ
【Transmitter Performance – Standard Conditions】
Item
Contents
１． Frequency tolerance
【Aeronautical stations】
　±0.0001%
【Aircraft stations】
　±0.0005%
　（Limited to those which apply to
RTCA　DO-186a/b.）
２．Modulation
5.6kHz or less
（The 8.33kHz systems based on RTCA/DO-186a are 6kHz or less.)
３．Output power tolerance
Maximum 20%
Minimum 50%
４．Modulation depth
A peak modulation factor of at least 85% shall be achievable.
５．Carrier noise
level
　　（Only aircraft
　　stations）
Shall be at least 35dB below the demodulated output obtained when the carrier is modulated 70% at 1,000Hz.
６．Audio frequency
response
Modulation frequencies of Hz are within 6dB,
７．Spurious emissions
① Tolerance of intensity of the spurious emission out-of-band.
　【Over 25W】
　　1mW or less and 60dB lower than the mean power of the base frequency.
　【1W to 25W or less】
　　25μW or less
　【1W or less】
　　100μW or less
② Tolerance of intensity of the needless emission in the spurious field.
　【Over 50W】
　　50μW or less or 70dB lower than the carrier wave power of the fundamental frequency.
　【25W to 50W or less】
　60dB lower than the carrier wave power of the fundamental frequency.
　　50μW or less
８．Others
Follow the rules for the radio equipment of Japan. ３