venerdì 28 luglio 2017

Propagation News – 30 July 2017

For most of last week there were no sunspots on the Earth-facing solar disc. A single small sunspot, number 2668, appeared on Tuesday, but had gone by Wednesday. Solar activity was very low and flux stayed at 69 and 70 all week. The K-index however was mainly at 3 and 4, and only briefly dropped to 1 by Thursday. The disruptive south-pointing Bz component of the interplanetary magnetic field reached a maximum negative value of minus 6 nanoteslas. The solar wind on that day impacted the ionosphere at 637 kilometres per second. The highest solar wind of the week, 707 kilometres per second, occurred on Monday.

Maximum useable frequencies for long paths were depressed throughout the period. Short range daytime propagation on 28MHz to several European countries was confirmed by the reception of numerous amateur station beacons, particularly from Spain. The 7MHz band proved its usual consistent role of being a main DX frequency at night-time. Many stations were on from Canada, USA and South America.

This weekend has been the Islands on the Air contest. Propagation may not have been conducive to high scores, although contests do have a habit of opening up bands thought to be closed.

Next week one or two old sunspots could rotate into view if they still exist. These were large on their first passage. If they do turn up, then we could see increased flux and a rise in maximum useable frequencies. Any solar flares arising may bring unsettled geomagnetic activity.

VHF and up:

We have a particularly unsettled period of weather over the country driven by low pressure systems crossing Britain until a weak ridge arrives at the end of the week. This means that GHz bands rain scatter is likely to be the best option for DX interest. It’s a good idea to use one of the many online weather radar displays to follow the heavier showers and point your dishes at them to look for beacons to alert you of possible rain scatter paths.

Staying with the unsettled part of the story, the strong jet stream, which is pushing all these lows across the country, will also be useful for sporadic E as it moves a bit farther into the continent, since the turbulence these jet streams create is one of the components for generating sporadic E.

The search for tropo will be a fruitless one as low pressure and breezy weather tend to prohibit the development of useful temperature inversions required for a good lift.

We’re back to high EME losses this week as we approach apogee on Wednesday and maximum negative declination on Friday. So there will be short Moon windows and poor conditions for EME in the coming week.

In all it looks like a week to do some nice, reliable, satellite operating, with the ‘birds’ unaffected by the vagaries of the weather and the lunar cycle.