Propagation News – 8 March 2015

Last week saw the solar flux index remain in the range 123-130. The beginning of the week saw rather unsettled geomagnetic conditions, with the planetary A index up to 23 at middle latitudes. Solar wind speeds remained elevated above 500km/s due to a geomagnetic storm that brought widespread aurora around the arctic circle.

The solar disk now looks quite bare compared with last week, and NOAA predicts the solar flux will decline to around 115 at the beginning of the week, rising to perhaps 130 at the end. In fact, the long-range forecast predicts these kind of numbers right through to mid April.

Geomagnetic conditions are predicted to remain fairly settled, with the Ap index lower in the second half of the week with a maximum of around five. This should bring reasonable HF conditions.

The Chilton Ionosonde at the Rutherford Appleton Laboratory near Oxford has been showing critical frequencies, where signals fired straight up are still just reflected back to earth, reaching highs of around 8-9.5MHz around lunchtime. This means that 7MHz remains useful for inter-G contacts during the day with maximum usable frequencies on a 3,000km path reaching 25MHz, and more than 28MHz on geomagnetically quiet days.

VHF and up propagation news

With high pressure on the charts continuing to play a role throughout the next week, albeit with a few exceptions, the conditions for VHF/UHF tropo propagation look fairly good and certainly worth checking the bands from time to time. The exceptions are mainly due to a small low crossing the country on Monday and a weakening cold front on Thursday. Outside these two events, the pressure remains high and capable of producing lift conditions, especially in the southern half of Britain and into the continent.

Stations in southern Europe are enjoying almost daily 50MHz trans-equatorial propagation (TEP) openings in the early evening so stations in the extreme south west of the UK should keep alert for any brief extensions northward.

We are still in the January to April lull in meteor showers, so keep looking for random MS contacts on the lower bands in the early mornings and aircraft scatter on the higher bands.

The Moon’s declination continues to fall all next week so UK EME operators will get increasingly shorter Moon windows with reducing path losses.

Category: GB2RS Propagation News