Propagation News – 27 September 2020

| September 25, 2020

We finally broke our long-running record of zero sunspots last week thanks to active region 2773. This new Solar Cycle 25 spot appeared over the Sun’s limb and pushed the solar flux index to 73. The end of the week also saw unsettled conditions due to a high-speed stream from a coronal hole. The hole in the Sun’s north-eastern quadrant pushed the Kp index to four on Wednesday evening and five by Thursday morning. A pre-auroral enhancement on Wednesday saw maximum usable frequencies (MUFs) rise to nearly 21MHz over a 3,000km path, but by Thursday morning they were struggling to reach 14MHz.

As the month has moved on we have started to see an improvement in HF conditions generally. Laurie, G3UML reported working ZL4RMF in New Zealand on 40m SSB at 0645UTC on Tuesday; and Andy, G3SVD worked FK8IK New Caledonia at 1006UTC on 20m CW. If you are looking for South Pacific contacts, Rob, F5VHN reports that Jim, E51JD on the South Cook Islands, is often on around 14.225MHz SSB most mornings.

Next week NOAA predicts the solar flux index will be around 70 again. The week may start unsettled thanks to a coronal hole, but the Kp index should improve as the week goes on. We expect HF DX conditions to improve as we move towards October and, hopefully, we can expect to see some more sunspots from the new Solar Cycle 25 as well.

VHF and up

The weather patterns at this time of the year can be very fickle as the major driving jet streams can be seriously distorted by former hurricanes from the USA side of the Atlantic. The predicted return of tropo after midweek, in the week just gone, was a bust for that reason. Other major distortions of the driving jet stream pattern are likely in the coming week, so the story is one of unsettled, changeable weather with periods of rain or heavy showers. That should mean another good week for rain scatter on the GHz bands, but tropo will not get much chance during this period.

Moon declination is rising this week, going positive late on Thursday night, so we’ll see longer Moon visibility windows as the week progresses, reaching a minimum on Thursday. Path losses are still increasing until we reach apogee on Saturday. 144MHz sky temperatures are low all week, but low peak Moon elevations early in the week won’t help.

The daytime Sextantids meteor shower peaked today but should still be active until 9 October. Continue to check around local dawn for the best random meteors—i.e. meteors that aren’t associated with any particular shower.

Category: GB2RS Propagation News