Propagation News – 25 October 2015

Propagation News – 25 October 2015

| October 23, 2015

This week has shown just how good the upper HF bands can be. A healthy solar flux index of 120 or more, plus settled geomagnetic conditions, has seen maximum usable frequencies rise to more than 30MHz. As a result, a lot of DX has been heard and worked, especially on 10 and 12m.

This weekend is the CQWW phone contest, so what can we expect? The SFI is predicted to remain in the range 120-130 and the K index is predicted to be two. This suggests that HF conditions may be good with maximum useable frequencies reaching and exceeding 28MHz on 3,000km paths. The US Solar Weather Prediction Center’s model is showing a low probability of any CME material hitting the earth, which bodes well for good conditions.

However, the risk of high speed solar wind stream effects that could reduce the MUF cannot be ruled out. Next week, the 29th and 30th are looking more unsettled with a potential K index of four. Assuming CME and solar wind problems don’t materialise we could have good HF conditions with upper band openings to many parts of the globe. Make the most of them as conditions may not be as good this time next year as solar cycle 24 declines.

Next week looks like we could have marginally-enhanced tropo conditions at first, with high pressure to the southeast of Britain. But overall it looks like a difficult week with a tendency for low pressure to dominate the charts through the period. Low pressure means the possibility of winter rain scatter on the GHz bands; never usually as intense as with summer storms, but even light rain can provide 10GHz and 24GHz enhancements.

The only other positive may come from any transient warm airstream ahead of a cold front later in the week, but this may only affect parts of the south and west, providing paths across Biscay towards Spain.

There are no major meteor showers this week, but there is not long to wait for the Leonids on the 17th and 18th of November. Keep looking for the usual early morning enhancement due to the increased number of meteoric particles swept up by the Earth. This is due to the Earth’s rotational velocity adding to the main orbital velocity.

Next week is a good one for EME operators, as we go through the ‘sweet spot’ where losses are still quite low, but declination and hence moon window length is increasing. There is up to 15 hours of moon visibility on Friday the 30th.
And that’s all from the propagation team for this week.

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