**Status update 01/05/2021: Maps are updating normally.
My blog pages contain occasional ramblings that you may find interesting (scroll down the left info bar to find them).
The page links are on the left-hand sidebar if you’re using a large screen, or touch the menu tab at the top right on mobiles. Tapping the cog on the left opens the information sidebar which contains live propagation warnings and a couple of items from my Twitter feed. On larger screens the sidebar is always visible.
The map size on the propagation map pages have been reduced slightly, but clicking on the map will open it in a new tab for a detailed view in full size.
Various other tweaks have also been made to the information pages. Note the addition of a new HF propagation map for N America, and rolling archive maps for the past 24 hours. A new meteor scatter map has also now been added.
The Sporadic-E Phenomenon
Sporadic-E, or simply “Es”, is mostly a summertime phenomenon, peaking between May and September in the northern hemisphere, and October and March in the southern hemisphere.
The causes of Es are not well understood and there and many theories, although it’s known that high levels of ionisation in the E-layer (80-120km altitude) cause radio waves to refract over long distances. A single hop can be somewhere between 400 and 2400km. Multiple hops are possible and in combination with F2 propagation, global communication on the 50 MHz band is know to occur. The Es “clouds” are sporadic in nature and can happen anywhere and at any time, although they are most common in the local summer with a late morning peak and a late afternoon peak. Extreme events can last several days and span the globe, or be localised to continents. Small isolated Es clouds can add to the magic, providing surprise contacts between specific locations.
HF Propagation and solar activity
This is a subject is too big to put in full here, but in a nutshell the radio frequencies between 0 and approximately 30 MHz can be reflected from the various layers of the ionosphere to a greater or lesser extent at different frequencies. Under good conditions the propagation can allow signals to travel half-way around the world, but the frequency bands for the best propagation change hourly and by season, and are also dependent on the amount of incident sunlight and current level of solar activity. During a solar storm (when the sun blasts out charged particles, and radio noise and X-Rays) these layers can be ionized to a much greater extent than is normally the case. The signals can then be blocked from escaping far enough from the Earth’s surface and not make it up to the higher layers for onward propagation around the globe. This is called a “radio blackout” which only affects the HF bands. Higher frequencies can also be affected by noise bursts.
My HF radio propagation maps can track radio blackouts. At onset the number of new inter-continental radio contacts on higher frequencies will become fewer, then lower and lower frequencies may be seen to be affected over a period of 15-30 minutes. The recover time is dependent on the strength of the storm, but could last hours or days. Follow my Twitter feed for live updates during solar storms.
If you see any problems with the website or have any suggestions for things you would like to see, please get in touch.
Andy Smith, G7IZU
Devon, England, British Isles, Earth…
Keep up to date via Twitter: twitter.com/g7izu
Note: Site-wide comments are disabled due to misuse. I can be contacted via Twitter @g7izu.