Propagation News – 21 January 2018
Last week saw unsettled HF conditions in the first half, but more settled ones later on. A high-speed stream from a coronal hole pushed the K-index to four and five last weekend, and maximum usable frequencies were depressed until at least Thursday. The HF bands were often very lacklustre, with even 20m struggling to show much DX, although the E31A Eritrea DXpedition was audible at times on bands up to 15 metres. The lower bands were humming though, with Andy, M0NKR reporting that he had worked Hawaii, KH7 on 40 metres.
Daytime critical frequencies are currently hitting a maximum of about 5.5MHz, which means 40 metres is not open to close-in contacts. For inter-G work we suggest that 80 or 60 metres would be the best options. Daytime maximum usable frequencies over a 3,000km path, derived from Chilton Ionosonde data and available at propquest.co.uk, are currently between about 18-22MHz around mid-day.
The 4U1UN international beacon on 14.100MHz is currently being heard in the UK on most afternoons, although the higher frequency 18.110 and 21.150MHz transmissions are generally more elusive.
Next week, we have the effects of another coronal hole to contend with. The high-speed solar wind, which may exceed 500 kilometres per second, is expected to impact the Earth by Saturday 20th, and we may see the K-index rising to five. After a potential short-lived enhancement, expect maximum usable frequencies to be adversely affected through to around Tuesday or Wednesday. The rest of the week should be more settled geomagnetically.
NOAA predicts the solar flux will remain hovering around the 70 mark, as the only sunspot visible is a tiny fleck, which looks very unthreatening.
VHF and up
The unsettled weather will continue into next week, but at least it may provide some strong rain shower activity at times, which is good for microwave band rain scatter. As a matter of interest, as the winter progresses, the seas cool and eventually maritime showers around the coasts become less significant for this propagation mode. We then have to wait for the land to warm in the spring and give us the familiar April showers!
The other VHF interest may involve some marginal tropo conditions over southern Britain later in the week as high pressure builds across the near continent. The effects may mainly be confined to southern Britain, with paths to Europe and perhaps across the southern North Sea to the Baltic.
We are now in the annual low in sporadic meteor activity, which lasts until the Lyrids shower at the end of April. This means that random meteor scatter contacts will be harder to complete.
The Moon’s declination is increasing this week and it is coming closer after last week’s apogee. With positive declination from Tuesday and falling losses, conditions will get better for EME as the week progresses. Lowest losses coincide with next weekend, so get those antennas pointing at the Moon.
Category: GB2RS Propagation News
