In 1843 the phenonema known as the Solar cycle was discovered by Samuel Schwabe a German astronomer who observed transitions of the Sun from periods of high activity to low activity every 11 years, over a period of nearly 20 years.
Put in simple terms, the Sun is composed of a huge ball of electrically charged hot gas. As this gas moves, it generates a powerful magnetic field. This magnetic field transitions through an 11 year cycle (known as the Solar Cycle) during which the magnetic poles of the Sun are transposed, ie the north and south poles change places.
This cycle affects activity on the surface of the Sun, such as sunspots and solar flares. The energy released by these events charges particles in the ionosphere, affecting radio propagation. More solar flares and sunspots occur at the peak of the cycle than at the bottom of the cycle. Typical values are 80-100 sunspots at the cycle peak and 15 or so at the cycle minimum.
When a strong flare occurs, the increased x-ray and extreme ultraviolet radiation produces ionisation in the lower, D (absorption) layer of the ionosphere, disrupting HF radio broadcasts by absorbing rather than reflecting signals.
We are currently at the end of Solar Cycle 24 (calculated as mid 2020), and from this point we can expect an increase in solar activity and changed radio propagation as the maximum useable frequency (MUF) for shortwave communications increases with an increase in solar activity.
At the peak of the Solar Cycle, the higher frequencies of the shortwave spectrum are very good. Low power stations can be heard over remarkably long distances.
At the bottom of the cycle, the current position, those higher frequency signals will not usually support normal propagation via the ionosphere. So propagation at lower frequencies will be better whilst higher frequencies will suffer.
Article written by Tecsun Radios Australia
Image of sun via Nasa.
Imagine flying off the coast over a vast ocean when your communications are lost.
Regular weather condition reports, particularly regarding strong headwinds are vital to the successful flight and landing of an airplane.
On July 9, an air ambulance departing Santiago De Chile to collect a patient on Easter Island lost satellite communications more than 1600Km from land.
Out of VHF range and with an inoperative satellite link, the fast thinking pilot tuned the aircraft HF radio to 7100Khz, the net frequency of the Peruvian Refief Chain who had just finished conducting a training exercise.
Fortunately for the pilot, 2 amateur radio operators Guillermo Guerra OA4DTU and Giancario Passalacqua OA4DSN, were still on frequency and able to respond to the aircraft. Together they communicated via HF with the aircraft and by telephone with the Ocean Air Control who have control of aircraft movements in the 32 million square kilometre Pacific Ocean Area off the coast of Chile.
Meanwhile other amateur radio operators rejoined the frequency ready to provide assistance if necessary.
OAC were already in a state of alert since losing communications with the aircraft and as the backup HF communications system at Easter Island was out of service.
After 10 or so phone calls between the amateurs and OAC, providing aircraft position reports and advising weather conditions over a period of 3 hours, VHF communications was established with the control tower on Easter Island, and the aircraft made a successful approach and landing.
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Article written by Tecsun radios Australia from Source: qrznow.com
Amateur Radio networks are providing worldwide communications and vital social communications during the current pandemic.
During the COVID-19 pandemic and subsequent lockdown, most of the population have resorted to Chat and video conferencing Apps to stay in touch.
Around Australia, there are hundreds of people staying in touch using an older, more traditional means, amateur radio.
Every day, regular Amateur radio “nets” (which are simply on on-air gathering of amateur operators) are in use, providing operators with a means of communicating with their fellow hobbyists on a daily basis. These “nets” appear at the same time, every day, and on the same frequency.
A net comprises several amateur radio stations, all operating in turn on the same frequency at a pre-determined time of day.
Nets for purely social use cover many subjects such as current weather conditions, ionospheric conditions, and propagation, equipment type in use, and modifications. These nets primarily use the 80 and 40 metre, amateur bands. They provide a great way to keep in touch, in isolation. Newcomers are always made welcome and shortwave listeners are also acknowledged by many operators.
Other examples of daily nets are the Kandos Net on 7093Khz, the Southern Cross Dx Net on 14238Khz, the ANZA DX Net on 14183KHz, and the Dx Net on 7130Khz (Monday, Wednesday and Friday).
There are also nets used for a specific purpose, such as the “Pacific Seafarers Net” on 14300Khz in the 20 metre amateur band, catering for amateur radio operators at sea. The Australian Travellers Network operates on 14.116 and 21,185Mhz. These 2 frequencies are manned from 1200AEST daily.
The amateur organisation WICEN (Wireless Institute Civil Emergency Network) also activates nets during emergency conditions. The east coast bushfires in 2019 are an example of this. When the NSW Govt declared a state of emergency, WICEN activated an emergency net and sent operators to provide logistical support for the RFS.
Specific emergency frequencies have been allocated for disaster support. They are: 3600, 7110, 14300, 18160 and 21360Khz. Amateur operators monitor these frequencies during natural disasters.
These nets make fascinating listening for shortwave enthusiasts, whilst providing an open communications link for those in isolation.
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