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CT2KCK > HF 01.06.16 17:06l 91 Lines 6782 Bytes #999 (0) @ WW
BID : 5421_CT2KCK
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Subj: Overview and History of Shortwave Radio
Path: IW8PGT<IZ3LSV<IK6ZDE<F1OYP<JH4XSY<CT2KCK
Sent: 160601/1452Z 5421@CT2KCK.CTLX.PRT.EU BPQ1.4.65
This is the use of electromagnetic waves to transmit and receive radio signals to a length of approximately 10 to 80 meters at
frequencies ranging from 1.6-30 MHz.
Shortwave radio uses skip propagation or sky wave to enable communication over long distances.
In this case, radio waves are usually refracted or reflected from the ionosphere back to the surface of the Earth enabling
communication to occur all around the Earth curve.
The early radio programming was done using long wave transmission.
However, this system had a number of drawbacks such as the required receivers, transmitters and antennas were very
expensive.
Also, the available spectrum for a long distance communication was very limited. In addition to this, beaming the radio wave to
be in line with the long wave was difficult, resulting in huge power losses over the long communication distances.
Before the 1920s, shortwave radio frequencies that were over 2 MHz were seen as useless for use in long distance
communication and were only used for amateur use. Shortwave communication came to be in the 1920s after successful
experiments of radio signals transmission over long distances.
This was done by bouncing the signals off charged particle layers in the ionosphere.
Transformation to shortwave was so successful such that by the late 1920s, over half of all the long distance communications
had converted from use of longwave signals and transoceanic cables and they had adopted the use of shortwave.
This was quite a cheap investment as the million-dollar investments for new transoceanic cables for telegraph and television
communication were no longer needed.
The expansive longwave stations were also no longer necessary.
However, some of those transoceanic cables and longwave communication stations still remained in operation until sometime
in the 1960s.
In addition, the radio operators made a discovery that shortwave bands allowed long-distance communication.
Previously, long distance communication was done using a surface wave propagation making use of low frequencies which got
attenuated during propagation.
The higher the frequencies and the longer the distances would mean greater signal attenuation.
This drawback, coupled with the difficulties encountered in the generation and detection of high frequencies is what made the
process of discovering shortwave propagation for commercial use difficult.
Since it is mainly influenced by sky wave propagation, shortwave radio energy can reach any point on the surface of the earth.
The occurrence of skip zones is one phenomenon of propagation of shortwave radio.
In these cases, there is a fail in reception.
At a fixed frequency of operation, a large change in the conditions of the ionosphere leads to numerous skip zones during the
night.
The sky wave propagation depends on:
The distance between the target receiver and the transmitter.
The time of day. Higher frequencies travel longer distances during the day.
The season.
Present Usage of Shortwaves
Shortwave radio broadcasting is largely used as a source of entertainment and news in most of the regions in the world except
those that are highly developed for example Japan, North America and Western Europe.
In these regions, commercial or government programming is done within different frequency bands.
Today, the top world broadcasting stations that heavily make use of shortwave include the Voice of Russia, The Voice of America,
The British Broadcasting Corporation and China Radio International.
Not only are shortwaves currently being used for international broadcasting, these techniques and frequencies are also being
utilized in long distance transmission of telegraph and telephone communications.
Operation of two-way portable radios and beginner radio stations is also at the frequency band of shortwaves.
Control rooms also use shortwaves to communicate to far away aircrafts and ships or for communication to remote areas where
other radio services and wired communication are out of reach.
Besides this, radio enthusiasts use shortwaves in two-way local and international communications for emergency and
educational purposes or just as a hobby.
So now, what is the future of shortwaves?
There is so much that shortwave has to offer. For one, this is a contemporary and relevant medium of conveying information
across the globe at an affordable cost.
This medium comes in handy for helping, educating and inspiring people from all around.
For this reason, shortwave will be here with us for a long, long time.
Numerous technologies that make use of the shortwave medium are being created every day. For this reason, we can confidently
say that there actually is a future for shortwave.
However, it has not all been good news for shortwave fans.
There has been a couple of bad news as far as shortwave is concerned.
Any keen listener of shortwave radio is up to date with the disappointing radio news. In June 2014, The Voice of America dropped
most of their services that used shortwave without giving any much of a warning.
In addition to the bad news, the Broadcasting Board of Governors (BBG), in their latest committee report, regarded to shortwave
radio signal as a technology whose listenership was dwindling over time.
They go ahead and cite the number of listeners from regions around the world.
However, they still do acknowledge that there are some communities that wholly rely on the shortwave mediums.
Radio Australia (RA) on the other hand is making major budget cuts through the Australian Broadcasting Corporation (ABC).
The main cuts that ABC are making involve the reduction of the shortwave offerings by RA. In the early 2015, after some
considerations, Voice of Russia also made a sudden drop of all the shortwave services they were offering.
A complete shortwave radio drop was surprising as no one had seen it coming.
Another major shortwave radio broadcaster, Radio Exterior de Espaņa was shut down in the late 2014.
Another sad news is that in August 2014, a non-profit station, Shortwave Radio Africa, lost funding leading to an automatic
shutdown. With all these misfortunes, we need to face the sad news that shortwave radio is declining.
If at all there is to be a future for shortwave, the following key factors should be considered:
Make use of user-friendly means of the way channels are allocated and accessed so as to attract more people.
Mobility should be enhanced such that one can carry a receiver in the pocket and also to allow for indoor reception.
Avail cheap shortwave receivers that many can afford,
Well, there still is hope for shortwave radio if at all the proper measures will be put in place.
In:
http://www.30mdg.net/overview-and-history-of-shortwave-radio/
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