Propagation News – 25 June 2017

| June 23, 2017

Last week the solar flux index remained steadfastly in the mid-70s. There was only one very minor S class solar flare, on Sunday, 18 June. As predicted, geomagnetic conditions were unsettled on the Sunday, but improved as the week went on.

During a week when we had the solar solstice, HF conditions were subdued. This is pretty much par for the course this time of year. A change in the ionospheric chemistry with more diatomic molecules and fewer monatomic species means it is harder to ionise. So, paradoxically, despite having more sunlight, maximum useable frequencies are lower during summer days. But, as we keep saying, you may find that 20m remains open much later in the evening. If we had some sunspots it might have even remained open all night.

Next week NOAA predicts more of the same with the solar flux index in the range 70-74. Monday may be a little unsettled geomagnetically, but then the rest of the week should be better with a K-index of around two.

At the moment, maximum useable frequencies over a 3,000km path are around 14MHz, with occasional openings up to 18MHz. After dark, 30m and 40m will remain the best bands for DX, with 20m probably closing in the late evening and usually before midnight. Sporadic E openings on the higher bands should also remain prevalent as we head towards the end of June.

VHF and up

Sporadic E is still the main DX mode through to August, and on 16 June we had one of the best events for a long time. Thousands of 144MHz QSOs were reported to Make More Miles on VHF, including contacts from South Wales into the Balkans.

The best policy to catch sporadic E is to maximise your chances by checking the bands late morning and late afternoon or early evening to capture the traditional two peaks of activity. Also look for late evening openings towards Iceland, Greenland and beyond. Check the beacons and clusters for signs of activity, remembering that an opening will build up in frequency as it develops—first 10m, then through 6m and 4m, to perhaps 2m.

Despite the heatwave, tropo conditions didn’t seem to materialise last week, with no cluster reports of 144MHz or above tropo QSOs over 600km from the UK.

Over the next week or so, it looks as if the changeover to low pressure will be completed and for much of the time there will be low pressure over Britain or nearby. This means that rain scatter will be the best GHz bands DX option. Tropo will not feature strongly again this week, but some short-lived overnight and dawn lifts are possible before the heat of the day breaks down any surface temperature inversion.

Today shows high and falling Moon declination, with low and increasing losses, so get your EME QSOs in the early part of the coming week.

Category: GB2RS Propagation News