International Comms

International Comms
What is High Frequency (HF) ?

High frequency (HF) is the ITU designation[1] for the range of radio frequency electromagnetic waves (radio waves) between 3 and 30 megahertz (MHz). It is also known as the decameter band or decameter wave as its wavelengths range from one to ten decameters (ten to one hundred meters). Frequencies immediately below HF are denoted medium frequency (MF), while the next band of higher frequencies is known as the very high frequency (VHF) band. The HF band is a major part of the shortwave band of frequencies, so communication at these frequencies is often called shortwave radio. Because radio waves in this band can be reflected back to Earth by the ionosphere layer in the atmosphere – a method known as "skip" or "skywave" propagation – these frequencies are suitable for long-distance communication across intercontinental distances and for mountainous terrains which prevent line-of-sight communications.[2] The band is used by international shortwave broadcasting stations (2.31–25.82 MHz), aviation communication, government time stations, weather stations, amateur radio and citizens band services, among other uses.

*Source of Information: Wikipedia; Link to Full Article: READ MORE ABOUT HIGH FREQUENCY

Some of the most popular High Frequency modulations used in Seychelles by Amateurs are:

  • SSB: Voice Communication using Microphone
  • Digital (RTTY): Digital modulation using computer connected to radio receiver or transmitter, Most Pupular ones are FT8 & WSPR
  • CW: Morse Code
  • WSPR (Weak Signal Propagation Reporter): Semi automated signal reporter

Below is example of low power HF propagation map populated by online WSPR (Whisper) Server. Those plots are are a combination of TX and RX's i.e. heard and hearing , in this case produced by S79RP in the period of 12hrs on 14.095 MHz on 14th Sept 2020.

WSPR Spots can be monitored with Live Update on the WSPR website: WSPR NET MAP WEBSITE
NOTE: WSPR Signals are used for propagation and antenna measurements and are not counted to radio operator logbook.

FT8 (WSJT-X Software) - DIgital Modulation for making registered contacts

FT8 stands for "Franke-Taylor design, 8-FSK modulation" and was created by Joe Taylor, K1JT and Steve Franke, K9AN. It is described as being designed for "multi-hop Es where signals may be weak and fading, openings may be short, and you want fast completion of reliable, confirmable QSO's".

Below is shown screenshot of a Map from DXMAPS.COM showing last 30minutes of activity both Transmitting and Receiving using Digital Modulation of FT8. Power output of the station have to be within your license limits, in this case it was transmitting with 50 Watts only. Frequency is Internationally approved , below is shown 20m band (14.074 MHz) at 15:00 14th Sept 2020 operated by S79KW.

All around the world activities can be seen with firly live update, it is important to make correct Band selection in order to see desired frequency displayed on the map. To see HF, we choose LF-HF on the left side of the screen and can apply more filters depending on the use.