Propagation News – 13 March 2016

| March 11, 2016

Last week we said that a geo-effective solar coronal hole looked like it might threaten the Earth, and we were right. Its open magnetic field allowed plasma to escape, impacting the Earth on Monday and sending the K-index up to six. This also sparked visible aurora, which were seen in southern UK.

This didn’t bode well for the HF bands, which continued to suffer all week as the K-index struggled to recover. Having said that, DX was workable at times. The TX7EU DXpedition in French Polynesia, for example, has been worked from the UK by some better-equipped stations.

This week NOAA predicts the solar flux index will be in the range 90-95. Geomagnetic conditions may be quieter at the beginning of the week, but storm conditions may return with a vengeance from Wednesday onwards.

Make the most of the slightly more settled conditions this weekend when the CW-only Commonwealth Contest should give you a great opportunity to work some rare DX entities with little competition from the rest of the world.

The K-index is predicted to hit four again on Wednesday and five for the rest of the week. So we can expect noisy band conditions, with lower maximum usable frequencies plus visible and radio aurora.

VHF and up propagation news

This may be a good week to look for DX on the multimode part of the bands. At last, we have the prospect of some longer lived tropo as high pressure over Scandinavia links up across the UK with the high near the Azores.

Throughout the week, high pressure will always be nearby, ending up over the North Sea or Scandinavia.

High pressure areas tend to develop temperature inversions in the lower atmosphere with the effect of changing the refractive index of the air over a short vertical distance.

In the right conditions, this can form a duct whereby VHF/UHF signals can travel over much longer distances than normal. These Spring systems are not usually as good as the Autumn ones, since the air below the inversion is often cold and dry, reducing the refractive index change.

The western side of Britain may have low pressure to deal with by the end of the week, but eastern areas across to Scandinavia and northern Europe should yield some results through to the following weekend.

This is another quiet week for meteor activity, and for EME operators the Moon reaches maximum declination on Wednesday. This gives long moon windows, albeit with increasing losses as the moon heads out to apogee.

Category: GB2RS Propagation News