Thursday, 22 May 2008

June 2008

Propagation Summary
A recurrent coronal hole (CH327) was in an Earth facing position on May 18-19. Another recurrent coronal hole (CH328) rotated into an Earth facing position on May 23-25.
Following a disturbance around 21st May, with the A index at 25, and the K at 5, conditions will have settled down by 23rd May, with the A index at 10 and the K at 3 where it will remain until May 31st with the A rising to 10 and the K index remaining at 3 until 3rd June when the A will drop to 5 and the K to 2.
The Solar Flux, however will drop from 72 to 68 by 25th May until 9th June when it will rise to 70. This is then followed by another rise to 72 by the 12th where it will remain until at least the 16th.
Long distance low and medium frequency (below 2 MHz) propagation along paths north of due west over high and upper middle latitudes is poor. Propagation on long distance northeast-southwest paths is fair.
(From, NOAA and

The Ionosphere
Scientists call the ionosphere an extension or a part of the thermosphere. So technically, the ionosphere is not another atmospheric layer, but a region of the atmosphere. The ionosphere represents less than 0.1% of the total mass of the Earth's atmosphere. Even so, it is extremely important!
The upper atmosphere is ionized by solar radiation. Under normal conditions free electrons and ions tend to recombine and a balance is established between electron and ion production and loss.
Ionization processes release energy, which heat up the upper atmosphere. So temperature increases with height in the ionosphere region to the extent that by 150-200km, the Earth's atmosphere is extremely hot compared to surface temperatures.
Different regions of the ionosphere make long distance radio communication possible by reflecting the radio waves back to Earth. It is also home to auroras and the mega-ampere currents that heat the atmosphere at high latitudes during geomagnetically active times. During storms, depletions and enhancements of ionization occur depending on the local time and geographical location.
Aeronomy is a term of recent origin, which is applied to the processes, both physical and chemical, of the ionosphere. From (University Of Michigan)

HF Propagation Predictions For 2008
Here is an interesting website by G4FKH, which has a monthly chart of predicted HF conditions listed by capital cities:
See also:

The New Shortwave Propagation Handbook (Paperback) - by George Jacobs, Theodore J. Cohen, R. B. Rose. The NEW Shortwave Progagation Handbook may well be the only book you'll need on the subject of ionospheric propagation! It is a "must read" for Radio Amateurs, Shortwave Listeners, and radio communicators of any type who need to make the most productive use of the radio spectrum, regardless of the time of day, the season of the year, or the state of the sunspot cycle. It will become your ever-present companion the operating table as you master the art of shortwave radio progagation. (Available from posted from the USA)
Thanks to KF and MET for regular updates.

Friday, 2 May 2008

Propagation Report May 2008

Propagation Forecast

The last week in April has been quite stable following a minor disturbance on the 23rd apparently caused by a coronal hole. Details at:
From 27th to the 30th, the index has remained at 5 and the K at 2. The first week in May will be quite disturbed. On the 2nd May, the A index will peak at 20 and the K at 5, then by the 8th May, conditions will settle with the A index at 5 and the K index at 2 until May19th when conditions are likely to deteriorate with the A index rising to 10 and the K index to 3. The solar flux has a downward trend remaining at 75 for the last week in April, then dropping to 70 by 2nd May where it will remain till the 19th May when it again rises to 75.

Propagation explained:
The Ionosphere: A collection of ionized particles and electrons in the uppermost portion of the earth's atmosphere which is formed by the interaction of the solar wind with the very thin air particles that have escaped the earth's gravity. These ions are responsible for the reflection or bending of radio waves occurring between certain critical frequencies with these critical frequencies varying with the degree of ionization. As a result, radio waves having frequencies higher the lowest usable frequency (LUF) but lower than the maximum usable frequency (MUF) are propagated over large distances.

The lowest part of the ionosphere, the D-layer appears at an altitude of 50-95km. This layer has a negative effect on radio waves because it only absorbs radio-energy, particularly those frequencies below 7MHz. It develops shortly after sunrise and disappears shortly after sunset. This layer reaches maximum ionization when the sun is at its highest point in the sky and this layer is also responsible the complete absorption of sky waves from the 80m and 160m amateur bands as well as the AM broadcast band during the daytime hours.

This part of the ionosphere is located just above the D-layer at an altitude of 90-150km. This layer can only reflect radio waves having frequencies less than 5MHz. It has a negative effect on frequencies above 5MHz due to the partial absorption of these higher frequency radio waves. The E-layer develops shortly after sunrise and it disappears a few hours after sunset. The maximum ionization of this layer is reached around midday and the ions in this layer are mainly O2+.
Highest part of the ionosphere. The F-layer appears a few hours after sunset, when the F1- and F2-layers merge. The F-layer is located between 250km and 500km in altitude. Even well into the night, this layer may reflect radio waves up to 20 MHZ, and occasionally even up to 25 MHZ. Ions in the lower part of the F-layer are mainly NO+ and are predominantly O+ in the upper part.
Thanks to Mike Terry and Ken Fletcher for regular updates.