September 2, 2016
This week brought a glimpse of better things to come. Andy, M0NKR reports he worked VP6J Pitcairn Island on 12 metres and the maximum useable frequency was often above 21MHz earlier in the week. The downside was, as predicted, periods of unsettled geomagnetic conditions, with the K-index hitting four at times and even six on Friday. But, looking on the bright side, as we enter September we are now heading towards better autumnal HF conditions in the northern hemisphere. The ionosphere is starting to cool and there is a shift towards more monoatomic and fewer diatomic species in the F2 layer. These are easier to ionise so we should start to see maximum usable frequencies increase. But we really need calmer geomagnetic conditions too, so look out for lower K-indices for better propagation on the higher HF bands.
Next week may see the solar flux index increasing thanks to large sunspot group number 2585, which is rotating into position on the solar surface.
The US Air Force predicts the Solar Flux Index will be around 105 this weekend, tailing off to 70 by the end of the week. Geomagnetic conditions may be unsettled at the beginning of the week, but improving by next weekend.
The smoothed sunspot number for September, for use with VOACAP-based prediction programs, is 35.
VHF and up propagation:
This week’s weather will be largely dominated by high pressure, meaning that we’ll be getting a chance to try some VHF and UHF tropo. In fact, for much of the coming week high pressure will extend across much of Britain and, at times, there should be some good quality temperature inversions to cause ducting over quite long distances.
Remember, tropo is not a fleeting signal path like sporadic E, but can last for hours or even days, with some variability. It is often better at higher frequencies, so try the GHz bands and UHF first, then move down to VHF. The positioning of the high should allow contacts from the UK to Scandinavia and down across Biscay to Spain, as well as within the UK itself. This is a chance to test out your station. Don’t rely on a repeater to do the work for you, go simplex and try other modes like CW and SSB.
Moon declination is negative all this week, meaning shorter moon windows. Add this to the Moon’s apogee on Tuesday, bringing the highest losses, and EME opportunities will be more limited.
The Orionids meteor shower is spread over many months between late August and mid-November, so continue to look out for improved meteor scatter conditions this coming week.