Propagation News – 25 February 2018

Despite warnings in the popular press that a massive solar flare was likely to cause chaos on Earth, we managed to survive! In the event, a coronal mass ejection, which was linked to the solar flare, caused the K-index to rise to five on Monday, the 19th, but conditions became more settled from Tuesday onwards. There was DX to be had if you looked for it. For example, ET3AA in Ethiopia has been very audible on 18MHz around lunchtime. Otherwise, the Sun has been more settled, with no visible sunspots and a solar flux index of 68 on Thursday—that’s just two points above what we can expect at absolute solar minimum.

As this report was being prepared a large coronal hole was visible, stretching from one solar pole to the equator. This might suggest we could have unsettled geomagnetic conditions on Earth from around Sunday, the 25th, although the NOAA figures don’t support this. Next week, NOAA predicts the solar flux index will remain around 70, so we can expect maximum usable frequencies to remain similar, with daytime band openings up to 17m and occasionally 15m. With night-time critical frequencies remaining around 3MHz, bands much above 40m remain mostly closed to DX.

VHF and up

It’s a cold, high-pressure story this week, and although technically this is a very strong high, the air underneath the temperature inversion that these highs produce is cold and dry. This is not particularly good at changing the refractive index of the air across the inversion and implies that this is not really the best option for tropo. It is better than flat conditions, and could possibly help out early in the mornings. A night of surface cooling gives a very low-level temperature inversion near the ground that could lead to a temporary improvement in tropo.

In the second half of the week it is likely that low pressure tracking westwards across southern Britain will bring the prospect of snowfall and perhaps icing on antenna wires and beam elements. It is always worth checking the tensions are good and shake off any ice build-up in this sort of weather.

We are still a month or so away from the return of Northern Hemisphere sporadic E, so the best opportunity for DX on the lower bands still lies in early morning random meteor scatter contacts.

The Moon is at maximum declination today so, combined with low path losses with perigee this Tuesday, it is a good week for EME.

Category: GB2RS Propagation News