Propagation News – 8 February 2015
As reported last week, the 2015 K1N DXpedition to Navassa Island in the Caribbean is now under way. If you would like to revisit the HF propagation predictions for the DXpedition, refer to last week’s GB2RS propagation entry. K1N has been audible on most bands and possibly loudest on 12m in the afternoon.
And now to the sun. The solar flux index has remained reasonably high, staying firmly in the 140s, although unsettled geomagnetic conditions saw the K index rise to 4 earlier last week. This was due to an elevated solar wind stream from a coronal hole, which brought widespread aurora to northern latitudes and had a detrimental effect on HF polar paths.
For the next week, NOAA predicts that the solar flux index will remain in the range 120-130, with the possibility of unsettled geomagnetic conditions next Sunday, 15 February. It should therefore be a good week for HF until then.
Paths to South Africa should have a 90-95 percent probability of success on 12m, that’s 24MHz, this week around noon, dropping slightly to 91 percent if you are on 10m, or 28MHz.
If you are using a VOACAP-based propagation prediction program you should now be using a smoothed sunspot number of 63 for February.
VHF and up propagation news
This coming week should be a good one for getting some quality VHF/UHF DXing done.
For the first time since this service started, we have a large high pressure system over the country. It’s going to remain with us for the whole of the week and should bring improved VHF/UHF conditions to most areas of the country and into Europe. The high will probably generate at least two significant temperature inversions, which can trap a layer of cool, moist air underneath warm, dry air just above the inversion.
This changes the refractive index of the air and bends the radio signals as they pass through the interface. The main elevated subsidence inversion due to the high pressure will vary in height from about 2,500m down to near the surface in the centre of the high.
The quality of this inversion will probably improve through the week and could provide extended elevated ducts, usually around the periphery of the high, rather than directly across the centre where the path may be ducted into the ground due to the lower inversion height.
The secondary inversion will be a night surface cooling inversion, very near the surface and may prove useful for shorter distances overnight and early morning inter-G working, but may decay or weaken as the temperature rises during the daytime.
Category: GB2RS Propagation News
