Propagation News – 26 February 2017

| February 24, 2017

Last week was a mixed bag as far as HF propagation is concerned. We had a solar flux index that got as high as 83, but this was tempered by unsettled geomagnetic conditions at times. The planetary K-index his four on Wednesday due to incoming plasma from a large solar coronal hole. And it varied from between zero and three for a lot of the week.

The good news is that there is quite a large sunspot group in the north-west quadrant of the Sun that should be pretty much Earth-facing by the time you read or hear this report. The bad news is that there is another coronal hole rotating into position. While Sunday the 26th and Monday the 27th will merely be unsettled with a predicted K-index of three, Tuesday the 28th and the rest of the week are predicted to be very unsettled with a possible K-index of six. These unsettled conditions could continue through to the end of the week.

At the moment we are seeing maximum daytime critical frequencies over the UK of about 6.6MHz. This means 40m is largely useable for contacts beyond 100 kilometres and we have daytime maximum useable frequencies exceeding 21MHz.

Looking on the bright side, next week we enter into March and head towards the spring equinox. This can be a good time for the higher HF bands, with better conditions on north-south paths.

VHF and up

I hope you managed to keep all the antennas intact and storm Doris passed uneventfully. The unsettled weather will continue through much of the coming week with no signs of any significant tropo to look forward to.

There is one brief period on Sunday when mild, windy and cloudy weather may give suitable conditions for a slight lift, in the region between a warm front and cold front. Given the speed that the weather systems are moving, it will be a short visit and soon gone. That leaves us with slow-moving low pressure nearby, but without large shower clouds at this time of year, GHz bands rain scatter will be limited.

There are no major meteor showers this week, but remember that the best time for random meteor scatter contacts is around dawn, when the Earth is rotating into the flux of meteoric particles.

The Moon reaches perigee on Friday, and its declination goes positive on Tuesday, so EME path losses are low and Moon windows will lengthen as the week progresses.

It’s a good week for EME, apart from today and Monday when the sun and moon are within a few degrees of each other giving high solar noise, especially at VHF where antenna beam widths are wide.

Category: GB2RS Propagation News