June 2011

Propagation Summary
May began with sunspot numbers of 115 dropping to 110 for 5 days on the 6th, then by the end of May sunspot numbers had dropped to 105. The Boulder A and K indices have remained at their ‘norm’ of 5 and 2 during May, except for the 9th and 10th, with a peak of 15. May should finish with a rise to 15 once more.
Sunspot numbers in June should start at 105 but are likely to drop to as low as 92 by Jun 13. The A and K indices should peak at 12 and 4 by June 11th.
According to the trend charts at: http://www.solarham.com/sunspots.htm the predicted sunspot numbers were back to predicted levels during April but sunspot numbers are likely to have fallen back by the end of May. From: http://www.wm7d.net/hamradio/solar/27d_forecast.shtml

Maximum Usable Frequencies
The estimated MUF’s for Western Europe, are 4 MHz (0100-0400), 5 MHz (0500-0600), 6Mhz (0700-1000), 7 MHz (1100-1800), 6 MHz (1900-2200) and 5 MHz (2300-0000). (Times in UTC). This and other regional estimates can be found at: http://hfradio.org/fot_7.html

Sporadic E
The Sporadic E season should be under way from around 1st May. Look for short skip on 15 and 10m. More details about sporadic E and HF propagation can be found in Steve Nichols’ blog and Podcast at: http://g0kya.blogspot.com/
Summertime Sporadic E, or Es as it’s often referred to, is one of the most exciting VHF propagation modes. This is especially true when the MUF reaches 144 MHz. Below is a guide to Summertime Sporadic E, what to listen for and how to work the DX.
What is Sporadic E?
There are three layers to the ionosphere F, D and E. We all know about the importance of the F layer to HF propagation and the way in which it refracts radio waves making world wide communication possible. The D layer and the E layer play little part in this, indeed they can have a detrimental effect to HF conditions by absorbing the transmitted signal before it reaches the F layer. This is particularly true of the E layer when it is heavily ionised.
During the summer months from May to September but in particular June and July, very intense clouds of ionization can occur. While not good for HF it does mean that VHF signals can be refracted by these clouds allowing contacts way in excess of the normal VHF range.
The cause of this intense ionization is unknown and of course very sporadic in nature. But some aspects have a degree of probability and with careful monitoring of the VHF range a good indication of a likely opening can be gained. Openings are more likely to occur early in the morning, early afternoon and in the evening although they can occur at almost any time.
From http://g3vre.org.uk/ES.asp (Chippenham and District ARC)

Solar Cycle Prediction
The current prediction for Sunspot Cycle 24 gives a smoothed sunspot number maximum of about 69 in June of 2013. We are currently over two and a half years into Cycle 24. Two consecutive months with average daily sunspot numbers in the 50s has raised the predicted maximum above the 64.2 for the Cycle 14 maximum in 1907. The predicted size would make this the smallest sunspot cycle in over 100 years.
Predicting the behaviour of a sunspot cycle is fairly reliable once the cycle is well underway (about 3 years after the minimum in sunspot number occurs. Prior to that time the predictions are less reliable but nonetheless equally as important. Planning for satellite orbits and space missions often require knowledge of solar activity levels years in advance. (NASA Solar Physics) http://solarscience.msfc.nasa.gov/predict.shtml
Links to these articles and more can be found at: www.jameswelsh.org.uk