Propagation News – 30 November 2014

The sun remained peppered with smaller sunspots this week, driving the solar flux index to a peak of 169. This kept the ham bands humming, with the maximum useable frequency easily above 28MHz on many paths during the daytime. Night-time highs reached 10MHz at times on longer paths, but 7MHz and 3.5MHz have both been better on shorter distances.

The latest NOAA/USAF forecast predicts the solar flux index will be 155 on Monday, reducing to 135 by the end of the week. This should be good enough for some reasonable 10 metre openings during the day. Geomagnetic conditions are predicted to be reasonably settled with the Ap index staying below 20 all week.

As we head into December you should be using 68 as the smoothed sunspot number for VOACAP-based propagation prediction programs, such as ACE HF and VOAProp.

Seven Megahertz, 40m, may be the band of choice throughout the night, with long-distance paths being possible during the hours of darkness.

There are better prospects for VHF/UHF propagation during the coming week as high pressure will make a welcome return to the charts. The resulting temperature inversions will trap cool, moist and sometimes foggy weather near the surface, overlain by warm dry air above the inversion, and this will produce contrasts in the refractive index of the air which will lead to improved ducting prospects.

High pressure will not be as strong in the far north, where it will also be rather breezy at times, so the better conditions are more likely in the southern and central areas of the UK. Occasional weak fronts may temporarily disrupt the ‘lift’, but high pressure should return afterwards.

Meteor scatter operators should be checking their systems as the Geminids shower peak is less than two weeks away. From the 7th of December we should start to see evidence of the shower to add to the regular morning and early evening random meteor peaks.

For EME operators, the Moon’s declination is increasing, meaning longer moon availability, but as the moon is moving out towards apogee, losses will increase.

And that’s all this week from the propagation team.

Category: GB2RS Propagation News