{"id":22093,"date":"2016-11-06T06:31:49","date_gmt":"2016-11-06T10:31:49","guid":{"rendered":"http:\/\/swling.com\/blog\/?p=22093"},"modified":"2016-11-06T17:12:42","modified_gmt":"2016-11-06T21:12:42","slug":"how-to-identify-changes-in-station-schedules","status":"publish","type":"post","link":"https:\/\/swling.com\/blog\/2016\/11\/how-to-identify-changes-in-station-schedules\/","title":{"rendered":"How to Identify Changes in Station Schedules"},"content":{"rendered":"

The shortwave bands are in a constant state of flux. And radio reception varies with the seasons. As a result, radio stations often need to alter their frequencies and times for best all-year-round reception at the listener\u2019s location. There are two seasonal changeovers: the \u201cA\u201d transmission period coincides with the northern hemisphere summer (March to October), and the \u201cB\u201d transmission schedule for the winter period (October to March). Leading up to these changeovers, broadcasters plan their schedules for the coming season. The B16 transmission season began last weekend.<\/p>\n

Want to improve your understanding of shortwave propagation characteristics? Study a few of the strategies employed by broadcast engineers at international radio stations during the twice yearly schedule changeovers. You’ll quickly learn much about how it all works!<\/p>\n

Frequency changes by international broadcasters allow you the opportunity to observe the factors that come into play at BOTH the transmitter site and the reception target zone in another part of the world. Broadly speaking, we know that when winter arrives reception of the higher frequencies declines and the lower frequencies provide better reception. The reverse applies in summer – reception on the higher frequencies are enhanced and ionospheric absorption of signals increases at lower frequencies.<\/p>\n

In addition, these characteristics change for both daytime and nighttime reception in summer and winter. Furthermore, some interesting reception opportunities occur in certain regions of the world during the summer and winter equinoxes. On top of this, factor in the 11-year sunspot cycle and the current monthly smoothed sunspot number (SSN). So, station engineers have quite a few variables to consider while selecting their preferred shortwave bands when targeting their signals to the listener’s location in some other part of the world! Perhaps one could even consider that these calculations as both a science and an art!<\/p>\n

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Next, the engineers representing each station have to sit down with their colleagues (competitors?) from other broadcasters and negotiate suitable frequency allocations in each of the preferred bands. This is why we have the existence of the High Frequency Coordination Committee (HFCC)<\/a>. Working together to find and register suitable frequencies that don’t interfere with other transmissions is an important part of successfully ensuring that everyone “wins”. The HFCC describes its role this way:<\/span><\/p>\n

The main objective of the HFCC is to provide the representation and services for the promotion of an efficient and economical use of the short-wave radio spectrum, and the improvement of radio reception of shortwave broadcast transmissions worldwide……<\/em><\/p>\n

HFCC’s main activity is a direct coordination of frequencies among frequency managers and specialists of broadcasters, administrations, transmission service providers and other organisations with the aim to facilitate the resolution or minimisation of mutual interference on short waves…..<\/em><\/p>\n

Membership of the HFCC is open to all individuals and organisations that provide frequency management and planning for recognised shortwave broadcasters.<\/em><\/p>\n

And it has to be said that the HFCC does a very good job at trying to resolve potential conflicts and clashes in frequency registration. But we didn’t always have this informal governing body. HFCC was only formed in 1990. Prior to that, there was much “rough and tumble” as stations tried to sort it out for themselves and avoid getting in each others way. Remember also, in the 1970s and 80’s there were many more shortwave broadcasters than there are today, each with very large operating schedules. For younger readers here, imagine the international bands being six or seven times busier than they are today!<\/p>\n

Understanding propagation characteristics, frequency allocation, antenna beam headings, different time zones and many other aspects of international broadcasting have been a source of fascination for me, both as a shortwave listener and as an amateur (ham) radio operator.<\/p>\n

Here are some things to consider when monitoring the change in transmission seasons:<\/p>\n