• HF news

    The sun remained spotless this week, other than the hint of a new sunspot coming around its limb as this report was being written.  

    The solar flux index reflected this, sitting around the high 60s, although it did reach 71 on Thursday morning. Geomagnetic conditions were quiet at the beginning of the week, but a solar wind stream from a large solar coronal hole was predicted to hit Earth later on Thursday the 19th. This normally means noisy HF bands, and depressed maximum usable frequencies (MUFs) after a possible initial positive phase.

    We are now seeing a shift towards more summer-like ionospheric conditions in the northern hemisphere. At this time there is a chemical change towards more diatomic molecules in the F2 layer and fewer monatomic species. The diatomic molecules are more difficult to ionise and as a result MUFs can suffer.

    Coupled with the lack of sunspots, we are now seeing daytime MUFs struggling to get above 16-17 Megahertz at times, despite the quiet geomagnetic conditions.

    The upside is that night-time MUFs are staying higher, with seven Megahertz possibly staying open to DX over a 3,000km path through the night. A phenomenon that has been spotted is that the MUF is sometimes rising again for a short period after sunset. It might be worth checking 14MHz around 2000hrs UTC as this has showed itself a few times on the ionosonde data.

    Next week, NOAA predicts the solar flux index will remain around 69 and geomagnetic conditions are predicted to be quieter from Monday onwards after the weekend's high K indices.

    These settled conditions could bring better DX from Tuesday or Wednesday, once the ionosphere has settled. As we'll explain in the VHF section, you may still have to wait a week or two before the start of the summer Sporadic E season.

    VHF and up

    Last week ended with high pressure near southern areas declining during the weekend as low pressure moved in from the Atlantic towards northern areas.

    There may be slightly enhanced Tropo conditions around at first but these could weaken as the low takes over. This could introduce showery weather with a prospect for rain scatter on the Gigahertz bands.

    The 2018 Sporadic E season is nearly here! It usually starts with a few fleeting SSB and CW signals across southern Europe, possibly not within range of UK stations, but with new digital modes, we might be lucky this early.

    Since the location of Sporadic E geographically can be influenced by the position of the jet stream, there may be some possibility of paths from the UK to the south-east into the Balkans and east to the Baltic states. The other possibility, based on expected jet stream positions, might be from Spain down to the Canaries.

    Anyway, before it all kicks off, it is worth making that list of useful beacons on 10m or 6m so that you can quickly find the openings – just Google “G3USF beacons”. Also, use the website to find the daily jet stream positions.
    Now we are in April, meteor activity is picking up again. The first significant shower, the Lyrids, peaks today, April 22nd, sometime between 1000 and 2100 UTC.

    Moon declination is still positive, but decreases all week, going negative (that is, South) this coming Friday. Losses will also increase as the Moon heads out to apogee, its furthest point from Earth. It’s another good week for EME then, with long windows and high Moon elevations.   

  • HF News

    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 18 MHz, and possibly even 21MHz, over this weekend.

    It is still a little too early for reliable Sporadic E openings on 24 and 28 MHz 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.

    VHF and up

    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, so 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 GigaHertz 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 and 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.