HF BROADCAST RECEPTION CONDITIONS EXPECTED DURING 2004
Prepared by George Jacobs, MSEE, Consulting Broadcast Engineer
P.O.Box
12298, Silver Spring, Maryland, USA
20908-0298
e-mail: e-mail: broadcaster@gjainc.com
web:
www.gjainc.com
Sunspot
Cycle 23 Progress
The present sunspot cycle, the 23rd to be recorded since the mid 18th Century, is in its seventh year of a statistical 11- year cycle. It began during October, 1996 with an official smoothed sunspot count of 9, rose to a peak of 121 during April, 2000. It began to decline as expected, but then surprised the experts by rising to a second peak of 115 during February 2002. It has resumed a slow decline since that date. It is estimated that during 2003 Cycle 23 dropped from a sunspot count of 81 at the beginning of the year to acount in the low 50s at year’s end. It is expected to continue its decrease during 2004, with an estimated count in the low 50’s in January, dropping to a level in the mid 20’s by December. Solar experts generally continue to predict that the end of Cycle 23 should take place sometime during late 2006 or early 2007. Figure 1 records the progress of Cycle 23, and its predicted future.
Sunspots are an indication of massive eruptions of ultraviolet radiation from the
Sun’s interior. This radiation is responsible for producing the ionosphere, a gaseous region high in the earth’s upper atmosphere. Somewhat like a mirror the ionosphere reflects high frequency radio waves, making it possible for HF broadcast stations to traverse large distances, cross frontiers, bridge oceans and link continents to reach a world wide audience. The higher the sunspot count, the stronger the ionosphere, and the higher the frequency range available for HF broadcast stations. While the strength of an HF broadcast signal changes little throughout an
entire sunspot cycle, the “window” of available HF spectrum diminishes as the cycle declines. .
Table 1 demonstrates this trend since Cycle 23 began its decline. Note that usage in the bands above 11 MHz dropped from 48% in 2000 to a planned 41% in 2004. Conversely, use of the bands below 10 MHZ increased from 52 to 59%. This data has been derived from the bi-annual coordinated schedules of the High Frequency Coordinating Conference (HFCC), and from comprehensive schedules published by ILG Radio Software.
For a more in-depth and fascinating discussion of sunspots and the
sunspot cycle see www.sunspotcycle.com.
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TABLE-1
Changes
in HF band usage with declining sunspot numbers 2000-2004
%
Band Usage
2000
2001
2002
2003 2004
2/3/4 2 3 4 4 4
5/6 13 14 15 16 17
7 14 15 15 16 16
9 23 22 22 22 22
11/12 17 17 17 17 18
13 4 4 4 4 4
15 14 13 13 12 12
17/18 9 8 7 6 5
21 4 4 3 3 2
26 * * * * *
* Negligible Usage
TOTAL
%
2-10 MHz 52
54
56
58
59
11-26 MHz 48
46
44 42 41
2004
Reception Conditions
The following is a general summary of reception conditions expected in
each high frequency broadcasting band during 2004.
.
HF Band Meter %
of Overall Reception
Characteristics
(MHZ) Band Usage
26 11 Negligible No propagation except occasional daytime. Perhaps just RFI on 25820 kHz to Africa,
21 13 2.0 While propagation is waning with sunspot decline, major world broadcasters likely to us during day for long north-south paths, i.e. Europe to southern Africa.
17/18 16 5.0 Day: long distance, all seasons
Night: occasional long distance, summer
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15 19 12.0 Day: mid and long- distance, all seasons Evening: mid and long-distance, except winter
13 22 4.0 Day: mid and long-distance, all seasons
Evening: mid and long distance, except winter
11/12 25
18.0 Day: short
and mid-distance all seasons
Night: mid and long-distance, except winter
9 31 22.0 Day: short and mid-distance, all seasons
Night: mid and long-distance, except winter
7 41 16.0 Day: short and mid-distance, all seasons
Night: mid and long-distance, all seasons
5/6 49 17.0 Day: short and mid-distance, all seasons
Night: mid and long-distance, all seasons
2/3/4 120/90/60 4.0 Day: short distance, all seasons
Night: mid-distance, all seasons
Short distance, up to approximately 1200 miles or 2000 km
Mid distance, approximately 1000 to 2400 miles, or 1600 to 4000 km
Long distance, beyond 2400 miles or 4000 km
Day: sunrise to sunset
Evening: Up to two hours after sunset
Night: sunset to sunrise
For specific times when reception of HF stations is expected to be optimum on various bands during 2004, refer to MOST SUITABLE FREQUENCIES 2004, which appears in the 2004 Edition of “The World Radio TV Handbook”. For more detailed schedule information, including languages broadcast, subscribe to “The Shortwave Guide”. Both may be available at your local booksellers, or from WRTH Publications Limited, P.O.Box 290, Oxford OX2 7FT, UK. .
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About the Author
With 63 years of experience in the development of governmental and private international broadcasting systems, George Jacobs is a legend in the field of International Broadcasting. He has successfully combined innovative engineering talents and diplomacy with a fierce belief in the free flow of information. George has received numerous awards and recognition from his peers, as well as a Presidential Commission. He is co-author of the popular New Short Wave Propagation Handbook, and is the Dean of Contributing Editors to the World Radio TV Handbook. This is the 41st consecutive year that he has written for us.