lunedì 7 maggio 2018

Propagation News – 6 May 2018

May 4, 2018

The sun remained spotless last week and the latest projections place sunspot minimum sometime around mid-2019. NOAA’s Space Weather Prediction Center says solar cycle 24 is declining more quickly than originally forecast, but expect the current solar conditions to last for at least another 12 to 18 months.

On the bright side, quieter geomagnetic conditions this week helped counter the low solar flux to provide the odd surprise. There has been F2-layer 20 metre propagation to the USA reported in the afternoons, but it was accompanied by rapid fading due to the maximum usable frequency just skirting 14MHz at times.

There were other highlights last week. We are starting to see sporadic E making an appearance. The FT8 frequency of 28.074MHz has shown some activity at times and special event station OE100WMA in Austria made a brief appearance on 10m CW on Wednesday morning. The good news is that sporadic E should strengthen as the weeks go on, so do monitor the higher HF bands.
Next week NOAA predicts the solar flux index will remain around 68, so F2 layer propagation will favour the lower bands, plus 20 and occasionally 17 metres. The lowest the solar flux index got down to during the last solar minimum was 65, in 2007 and 2008.

Another coronal hole became Earth-facing on Thursday, so we may expect unsettled geomagnetic conditions from Saturday, the 5th. Its extended elongated shape means these could last until Tuesday or Wednesday, with a maximum K-index of five. After a positive initial positive phase we may expect subdued maximum usable frequencies, poor HF conditions and noisy bands as the geomagnetic storm develops. Thursday the 10th, through to Saturday, 12 May, look to be more settled and may offer the best opportunities for DX.

VHF and up:

After some very wet weather recently, we have high pressure making a welcome return. This will be centred over Biscay, across to southern Scandinavia as an elongated ridge. This should give many areas a chance of tropo, probably favouring paths to the south-west and south across Biscay to Spain, but there may also be some options to the east, although not as solid. The ridge should last for much of next week, so there is plenty of time.
As mentioned earlier, the sporadic E season has started for FT8 and is putting in the odd appearance for CW and SSB. Since the present set of openings have tended to be associated with the location of jet streams in the upper atmosphere, it makes sense to see what the charts offer for next week. Sadly, there is a marked lack of jet stream activity in the nearby region of Europe, which we may need for sporadic E paths from the UK. Indeed, it may be a thin week, unless one of the other possible weather triggers, a strong ridge pattern, is enough to do the trick, but it’s not often something we see early in the season. Check the beacons and clusters for band reports and the sporadic E blog on, which may give some useful pointers.

For meteor scatter operators, the Eta Aquarids shower will peak before dawn this Sunday, but the shower really favours the southern hemisphere. The smaller Eta Lyrids peak on Wednesday.

The Moon reached minimum declination and apogee yesterday. Declination only goes positive next Saturday, so EME windows will be short, but lengthening, and losses will fall as the week progresses.