Propagation News – 31 May 2015

| May 29, 2015

As predicted, the sun was a little more settled this week, with the solar flux index being below 100. There were no X-class solar flares to black out HF either. Geomagnetic conditions were also settled with the Ap index at middle latitudes remaining in single figures. The Kp index, which is a better indicator of real-time conditions as it is updated every three hours, was also mostly at one or two.

So, overall, HF conditions were settled and long-distance DX was possible, although we are now entering the summer doldrums when maximum usable frequencies tend to be poorer than in winter during daytime.

To confirm this, the noon ionosonde plot taken at Chilton on Wednesday showed a critical frequency of 6.4MHz and a predicted maximum usable frequency over a 3,000km path of less than 20MHz. This means that 20m and 17m might remain the optimum bands for DX, while Sporadic-E will offer short skip on higher bands. It also shows that 7MHz might not always support close-in inter-UK contacts and 5MHz might be a better bet.

For the coming week, NOAA predicts the solar flux index will be around 110-125 with unsettled geomagnetic conditions on Tuesday and Wednesday when the K index may hit four, due to a recurrent coronal hole and high speed solar wind.

VHF and up propagation news

Sporadic-E was fairly active last week, with 70MHz openings as far as the Canaries and a brief appearance of 144MHz Es to Portugal on Wednesday. This was probably due to an abundance of useful jet streams, which can generate the wind shear required. The jet stream pattern will become confined to the northern fringes of Europe in the week ahead, so paths to Scandinavia may bear fruit.

Next week is historically one of the best weeks of the Sporadic-E season, with good openings to the Americas often reported around June 6th, so be vigilant and you should work some nice DX.

As for tropo, next week will start with an area of low pressure over the country, so we are unlikely to see any enhancement until after mid-week when a ridge of high pressure will develop making it worthwhile checking the VHF/UHF bands for lift conditions especially overnight and early mornings.

There is the potential for some thundery showers up to mid-week, so look out for rain-scatter on the upper GHz bands. No significant meteor showers this week, and the Moon reaches its most southerly declination on Wednesday so this is a week to focus on Sporadic E on the low VHF bands.

Category: GB2RS Propagation News