Propagation News – 2 November 2014

Giant sunspot region 2192 has now disappeared around the back of the sun and luckily it didn’t produce any major coronal mass ejections to upset HF conditions while it was visible. The region was, however, the source of numerous solar flares over the past two weeks, which caused a number of sudden ionospheric disturbances or fadeouts. When these occur it is still worth checking the higher HF bands, like 28MHz, since absorption is less at higher frequencies.

Solar Flux Index levels this past week have been in the wide range of 217 to 150. The SFI is now lower, but conditions will remain good, as long as the K index remains low.

The smoothed sunspot number for November, for use in HF prediction programs like VOACAP, is currently 69.

For HF contacts around the UK, 7MHz remains the best option during the day, with the critical frequency falling after dark. 80m may be a better option in the evening.

For paths to the East Coast of North America, the optimum working frequency should be 18 or 21MHz in the afternoon with a reliability of around 80%. Contacts on 28MHz should also be possible with a reliability of about 75%.

And now the VHF and up propagation news. The weather in the coming week will be very unsettled with a large area of slow-moving low pressure near northwest Scotland, followed by a second major low late in the week. These will produce strong winds at times and generally preclude enhanced tropospheric propagation. However, intense convection of cold air over warm seas will produce large cumulonimbus cloud and heavy showers, which may give some rain scatter opportunities on the upper GHz bands, chiefly near western coasts.

A weak ridge of high pressure may transit the country midweek and could develop temporary temperature inversions, which would marginally improve tropo prospects, although these are likely to be very minor. Lower solar disturbance means a low probability of VHF auroral propagation.

We will begin to see the onset of the Taurids meteor showers, which peak on the 11 and 12th November, albeit with a low zenithal hourly rate of around five. Remember that the best time for random, non-shower, meteor scatter contacts is around dawn.

And that’s all for this week from the propagation team.

Category: GB2RS Propagation News