HF ©2007 Thomson Higher Education

 

HF


The High Frequency (HF) band of radio waves includes the range from 3 to 30 MHz inclusive. HF is a major part of the shortwave band of frequencies which are used for long distance communication, including intercontinental distances. The band is used by international shortwave broadcasting stations, aviation communication, government time stations, weather stations, amateur radio and citizens band services, among other uses.

 

How it works

propagation of HF radio
Image: radartutorial.eu HF radio waves bounce off the ionosphere and can be received over the horizon. These waves can travel huge distances and higher frequencies generally have greater ranges. TMR has even picked up transmissions from the US Coast Guard base in Kodiak Alaska.

Different frequencies reflect from different ionospheric layers whose density and height varies between day and night. At night reception tends to be better, but this is affected by meteorological conditions which makes HF reception extremely difficult to predict. Vessels on long voyages in the South Pacific or in New Zealand can communicate with us.

 

Which Band to Use

Try to use the lowest HF band that will give clear communications. If unsuccessful try the next higher band. A general guide of distances and appropriate bands is shown below, but remember that HF is affected by atmospheric conditions and the guidelines below are not absolute.

Approximate DistanceDayNight
  Less than 300km 3 - 4 MHz 2 - 4 MHz
  Between 300km & 750km 5 - 6 MHz 3 - 7 MHz
  Between 750km & 1,500km 5 - 9 MHz 6 - 10 MHz
  Between 1,500km & 2,500km 8 - 12 MHz 7 - 11 MHz
  Between 2,500km & 5,000km 10 - 18 MHz 8 - 15 MHz

 

Note that Tas Maritime Radio operates only the bands shown below.

 

Frequencies

Tas Maritime Radio operates HF in the 2, 4, 6 and 8MHz frequency ranges. The table below lists the distress safety and calling frequencies and working frequencies for these bands.

  BandDistress/calling frequency †Working frequency
  2 MHz   2524 kHz
  4 MHz 4125 kHz 4146 kHz
  6 MHz 6215 kHz 6227 kHz
  8 MHz 8291 kHz 8294 kHz

 

† do not use these frequencies for conversations and always return to them when not using your radio.
‡ 2MHz does not have a distress channel as such - this is a pleasure craft working frequency.

 

Skeds on HF

TMR conducts skeds on the working frequencies listed in the table above. A pre-announcement is broadcast on the calling channels (as well as 2524kHz) and vessels are asked to select a working frequency to listen to the sked.