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Propagation News – 8 April 2018


April 6, 2018

Last week saw a continued lack of sunspots as we journey towards solar minimum sometime in 2019–2020. The solar flux index hovered around 68-69, which is only about two to three points above what we can expect when it hits its lowest point. Unfortunately, we are likely to be repeating this sentence quite a lot over the next 12 months or so!

There were no solar flares reported and geomagnetic conditions were relatively calm, with a maximum planetary K index of two. This was due to a lack of earth-facing coronal hole activity, but that isn’t going to last. Next week, the solar flux index is likely to remain around 68, but we can expect unsettled geomagnetic conditions, with the potential for depressed maximum usable frequencies and noisy bands, from the 11th to 15th, as a large coronal hole on the solar equator become geo-effective.

Despite the low solar flux, the current settled conditions means there may be good DX to be had up to 18MHz, and possibly even 21MHz, over this weekend.

It is still a little too early for reliable Sporadic-E openings on 24 and 28MHz and we may need to wait until the end of April or early May, but do check.

Looking more generally, we are starting to see a shift towards more summer-like ionospheric conditions in the northern hemisphere. Daytime maximum usable frequencies may be lower than they were in winter, and east-west HF paths are likely to be worse. But the good news is the HF bands may stay open longer in the evening.

We are already seeing 20 metres remaining open until around 2100 UTC on 3,000km paths, and 40m and 80m continue to be worthwhile evening bands as well.

It looks like another week of uncertain fortunes, although unlike last week, there is at least the hint of high pressure to the northeast of Britain, favouring some potential Tropo conditions from the north of the country to southern Scandinavia and the Baltic. The south of Britain may just be far enough away from the high to see some heavy April shower activity and possible rain scatter on the microwave bands, especially in the southwest.

Now another mention for Sporadic E, which at times of thin HF propagation can liven up 10m, and of course the more traditional 6m bands. The weather patterns can influence this by the distribution of jet streams, and daily charts are available on along with occasional commentary.

The long winter meteor minimum is drawing to a close soon, with the April Lyrids coming up on the 22nd, so get prepared for better reflections. We’ve just passed minimum Moon declination for the month. Apogee, the point where the moon is furthest away from Earth, is today, so losses are at their maximum and Moon windows are short. We are a week away from declination going positive again, but conditions will slowly improve throughout the week.
And that’s all from the propagation team this week.

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