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Radio frequencies for shortwave

Do you enjoy listening to shortwave and have noticed the frequencies used by your favourite broadcaster change twice a year? Interestingly there is a scientific reason behind this.

Shortwave travels long distances because of its unique way of propagating. The transmission is beamed upwards towards the sky where it is reflected back down to earth spanning a huge distance between the two points. In good conditions a single transmitter is able to reach millions of listeners around the world.

This is what makes shortwave unique and incredibly effective, especially to remote audiences as well as to areas where news and information is highly controlled. 

As a general rule, higher frequencies (SW) work best during daylight hours and summer time while lower frequencies (MW) work better in darkness – before dawn and during the long winter evenings. 

 This same frequency can not be used all year round because as the seasons change the number of daylight hours at any location can directly affect the optimum frequency band. This is because the energy from the Sun required to ionise reflective layers in the upper atmosphere is directly impacted by the sunlight hours available. So seasonal changes causing shorter sunlight hours will affect daily propagation of a higher frequency, and so a lower frequency will need to be chosen to provide similar coverage during the period of shorter days.

The High Frequency Coordination Committee (HFCC, under the ITU International Telecommunications Union) is the body that has the responsibility to decide when to change shortwave  frequencies.They must coordinate these changes with all the major shortwave broadcasters around the World.

To ensure the optimal transmission conditions the HFCC recommend  two seasonal frequency schedules – summer and winter – known as the ‘A’ and ‘B’ seasons.

The changeover between seasons is internationally agreed to occur on the last Sunday in March (start of ‘A’ season) and the last Sunday in October (start of ‘B’ season), which coincides with start and end of ‘Daylight Saving’ in many countries, where local time can change.

The changeover ‘A20’ season has just occurred on Sunday 29th March, and the frequencies agreed for all shortwave transmissions will continue until the beginning of the next season ‘B20’, on Sunday 25th October.

Easily identify shortwave stations

For those of you who have ever been scanning shortwave radio and happened across an interesting station but have no idea what it is or where it is coming from there are a couple of phone apps that can identify what you are listening to.

 

These 2 apps (depending on what type of phone you have) will help listeners identify who they are listening to.. All they need to do is lookup the frequency they are receiving  and these Apps will show what stations are on air at the time. This is an easy way to identify who you are listening to.

 

                                                                                                                                          For Android: Click here

shortwave station identifier.

                                                                                                                           For iphone, iPad;Click here   Shortwave station identifier

Try these two apps and let us know what you think. We would also love to hear what you have found recently on Shortwave. 

Send your feedback and listening reports to hello@tecsun.com.au