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Annual Review 2004/05
 
 
Measuring our performance - Short Wave Audibility
Audibility reports are based on data from the total number of signals monitored. Quality is rated as follows:

5 very good
4 good
3 acceptable
2 poor
1 unacceptable

Percentage of all short wave signals scoring 3, 4, or 5:

  2003/04
Actual
2004/05
Target
2004/05
Actual
Global 83 86 81
Africa and the Middle East 86 87 83
Americas 77 76 64
Asia and the Pacific 83 85 82
EurAsia 82 88 81
Europe 90 93 86


Long distance transmission via the ionosphere is affected by many different factors, including the level of sunspot activity, which has an approximately 11-year cycle. During periods of high sunspot activity, daytime transmissions can use higher frequencies, more of which are allocated for broadcast use, whereas around sunspot minimum, which we are in at present, lower frequencies must be used in order to reach the target areas. Congestion in these limited lower-frequency bands is a serious issue, as the additional frequencies needed to ensure good audibility are often not available because they are in use by other broadcasters.

Measuring our performance
Short Wave Audibility
 
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