Thursday 19 May 2016

Sporadic E season is under way

The Sporadic E (Es) season on 10m and 6m is well under way with lots of useful openings.

I was having a listen around 28MHz today and was struck by how many 10m beacons are audible when there doesn't appear to be any other activity on the band.

And they aren't high powered either. First I heard OK0EG on 28.2825MHz in the Czech Republic and a little late OY6BEC in the Faroes on 28.235MHz. Then a little later still I spotted a spike on the IC-756 Pro3's panadapter and it was F5ZWE near Toulouse on 28.2427MHz.

You can get a current list of 10m beacons, complied by Martin G3USF, at:

These are all running 10-15W and simple antennas, yet can reach S6-9 in the UK when the conditions are right.

We still don't completely understand Sporadic E, although the current thinking is that it is due to wind shear in the upper atmosphere that pushes ions together into clumps or clouds. The ions may come from meteors. Jim G3YLA, who is a professional meteorologist, is also looking at whether these winds, when they pass over mountain ranges, are forced upwards and create these "gravity waves" that force the ions together.

I also have a theory that solar flares can contribute to SOME of the ionisation on occasions, but mainly outside of the May-August period - there are plenty of instances of Es without any flare activity. I have some plots of Es in late April that correlate very well with solar flares.

Anyway, Jim posts some daily high-level wind charts in an attempt to understand what is happening. 

Steve G0KYA


  1. Winter appearances of Polar Mesospheric (non-summer) Echoes are shown now to be almost certainly down to meteoric input. The non-summer echoes are related, to varying degrees, to the appearance of Es in winter. As you imply, the situation is quite complicated, made more so by the inaccessibility of that height in the atmosphere.

    It's useful to look at photos of noctilucent clouds, which are also nucleated around iced, charged meteor debris in summer. These reveal the gravity wave structures visually, which are essentially identical to what is going on with Es clouds.

  2. I believe that noctilucent clouds have been linked to Summer Solstice Short Path (SSSP) propagation between Japan and Europe on 50MHz . When I first suggested this as a possibility I was shouted down, but I understand that reflections have been seen using a 46.5-MHz radar system at Aberystwyth in Wales.