venerdì 3 marzo 2017

Propagation News – 5 March 2017

We were pleased to get the HF propagation prediction pretty much spot on last week. While Monday and Tuesday were reasonably settled, Wednesday saw the effects of solar material from a large coronal hole as it hit the Earth. The K-index leapt to five around lunchtime and there were reports of HF openings up to 10 metres. This was probably a pre-auroral enhancement, but it didn’t last too long.

By late Wednesday the K-index had continued to climb to six. And on Thursday morning this had taken its toll on the ionosphere; the maximum usable frequency was down to less than 14MHz, with unsettled conditions all day. Next week, NOAA predicts a solar flux index in the low 70s and a K-index of two, thanks to a respite from coronal hole activity.

Interpreting this, we can say that HF conditions should be better than they were in the latter half of last week. Expect maximum usable frequencies to reach perhaps 21MHz at times. After a few days with a low K-index we may even see some better DX. This time of year favours north-south paths, such as the UK to South Africa, South America and the Caribbean. Paths to Cape Town may even reach 28MHz around 1400UTC for well-equipped stations if geomagnetic conditions are quiet. That is, with a low K-index. In contrast, paths to the Caribbean may struggle to reach 21MHz.

As we are now into March, users of propagation prediction software like VOACAP and VOAProp should be using the new smoothed sunspot number, 28.

VHF and up:

This week starts as unsettled as the last, but without the extremes of Storm Doris! We had some rain scatter last Tuesday but, true to form, it was just about gone by the start of the SHF UKAC contest. This just highlights the need to operate on the GHz bands more than one day a month, unless you just want to work the same people and no DX.

This week we have regular small lows drifting across the country and producing more areas of rain or heavy showers. In fact, as we move towards the equinox, the chances of heavier showers developing increases and, although this may mean potential thunder and lightning, it does improve the prospects for rain scatter on the GHz bands.

This takes us up to midweek, after which there is a hint of higher pressure over Biscay and France, possibly bringing slightly better tropo prospects to southern areas. But some longer-range models bring a return of unsettled weather after a day or so.

We are still in the period until April with no meteor showers, so stick to the best time for random meteor scatter contacts, which is around dawn, when the earth is rotating into the flux of meteoric particles.

The Moon reaches its highest declination on Tuesday and losses are still low in the early part of the week, so it’s another good week for EME.