sabato 2 luglio 2016

Propagation News – 3 July 2016

The Sun has had another virtually spotless week with the solar flux index keeping stubbornly below 80. As we said last week, this is getting close to the kind of figures we expect to see at sunspot minimum, such as when the SFI touched 64 in June 2007. Geomagnetically, things were a little more settled than previous weeks with the K-index generally being two or three.

On Thursday a large coronal hole had rotated into a central position on the Sun, suggesting its plasma output could become geo-effective. If correct we could expect the K-index to soar this weekend, with the chance of visible aurora.
NOAA predicts the solar flux index will be around 80-82 over the next seven days. Other than the potential for unsettled geomagnetic conditions this weekend, the rest of the week looks like it could be better.

The Chilton Digisonde plots show the noon critical frequency as just below 5MHz on Wednesday, giving a predicted maximum usable frequency over a 3,000km path of about 17.8MHz. If you want to work DX via the F2 layer you may need to stay on 14MHz/20 metres during daytime. However, sporadic E should still give strong short-skip conditions at times on the HF bands from 20 metres upwards. Meanwhile, if you do work any decent DX on HF please tell Steve, G0KYA via email to

VHF and up propagation news:

The first hour of the GHz Bands UKAC last Monday brought some rain scatter propagation and the unsettled weather this coming week means more showers will be around again. This is likely to give more rain scatter for the GHz bands.
However, the main DX mode, tropo, needs areas of high pressure to succeed and the next week does seem dominated by low pressure for much of the time. Only at the very end of the week may we see a ridge from the Azores high move across southern Britain. This could give some limited tropo paths in the south and down across Biscay towards northern Spain.

The DX mode of choice at this time of year is still sporadic E, and recent events have confirmed the season is still in full progress. With recent openings to Spain on 2m, all the traditional VHF bands are in play from 10m up to 2m. The position of the jet streams are again likely to favour paths to south-east Europe round to Spain. If your shack time is limited, a good choice for sporadic E activity is late morning and early evening.

The Moon declination is positive, but the Moon’s orbit is taking it further out, meaning losses will rise towards the end of the week.