Modern Trends in Hf Communication
MODERN TRENDS AND TECHNIQUES IN HF RADIO COMMUNICATION
CHAPTER I
INTRODUCTION
OVERVIEW
In times of increased necessity for international crisis management, secure and protected Radio communications especially at sea are more important than ever before. Mobile Naval forces require reliable, jam resistant and secure voice and data connections. Standardized communication media, such as email, internet via radio, has long been part of today’s naval communication and is now indispensable.
Even today, entire frequency spectrum of VLF, LF, HF, VHF, and UHF, as well as UHF, SHF and soon also EHF SATCOM is used to set up communication with units and forces at sea. Which of these transmission media is selected depends mainly on the availability of the information channel in terms of coverage range, transmission speed and, last but not the least, required data rate. However, the decisive factor is, and will continue to be, the geographical distance to the receiving station. We can distinguish between three such distances as line of sight (LOS), extended line of sight (ELOS), up to approximately 300 NM and beyond line of sight (BLOS) for coverage beyond 300 NM. Two viable options available for communication beyond line of sight and worldwide are following:
• High Frequency Communication (2 to 30 MHz) • Satellite Communication
HF COMMUNICATION
[pic]
The key benefit of HF Radio is that it provides communication over very long distances (worldwide with a suitable aerial). It achieves this with "sky wave" communication, where the HF signal is reflected off the ionosphere (illustrated above) for long distance communication, or using Near Vertical Incidence Skywave (NVIS) for shorter distances. This benefit comes with a number of drawbacks: • Slow speed. Rates vary from 75 to 12,800 bits per second, with 1,200 bits per second typical. This is insufficient to support many desirable applications. • Cannot
CHAPTER I
INTRODUCTION
OVERVIEW
In times of increased necessity for international crisis management, secure and protected Radio communications especially at sea are more important than ever before. Mobile Naval forces require reliable, jam resistant and secure voice and data connections. Standardized communication media, such as email, internet via radio, has long been part of today’s naval communication and is now indispensable.
Even today, entire frequency spectrum of VLF, LF, HF, VHF, and UHF, as well as UHF, SHF and soon also EHF SATCOM is used to set up communication with units and forces at sea. Which of these transmission media is selected depends mainly on the availability of the information channel in terms of coverage range, transmission speed and, last but not the least, required data rate. However, the decisive factor is, and will continue to be, the geographical distance to the receiving station. We can distinguish between three such distances as line of sight (LOS), extended line of sight (ELOS), up to approximately 300 NM and beyond line of sight (BLOS) for coverage beyond 300 NM. Two viable options available for communication beyond line of sight and worldwide are following:
• High Frequency Communication (2 to 30 MHz) • Satellite Communication
HF COMMUNICATION
[pic]
The key benefit of HF Radio is that it provides communication over very long distances (worldwide with a suitable aerial). It achieves this with "sky wave" communication, where the HF signal is reflected off the ionosphere (illustrated above) for long distance communication, or using Near Vertical Incidence Skywave (NVIS) for shorter distances. This benefit comes with a number of drawbacks: • Slow speed. Rates vary from 75 to 12,800 bits per second, with 1,200 bits per second typical. This is insufficient to support many desirable applications. • Cannot