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Propagation News – 30 August 2020

It was a quiet week, with zero sunspots and relatively quiet geomagnetic conditions and a maximum Kp index of three. After the new sunspots appeared over the past few weeks it did look like Solar Cycle 25 was getting under way. But now it looks like we may have to wait a little longer, languishing at solar minimum for the next couple of months.

It was not all bad news though. Laurie, G3UML reports good conditions on 20m SSB. He worked A25 Botswana and ZS3 South Africa, plus Ross, ZL1WN in New Zealand via the long path. Laurie said signals from the Middle East were also strong.

A series of narrow coronal holes are now beginning to partially face Earth. An elevated coronal hole stream should begin to move past Earth by Saturday, 29 August which could lead to an elevated Kp index and visible aurora at higher latitudes.

Other than that there is little to see on the STEREO Ahead spacecraft imagery. Barring surprises, this suggests the Sun will remain quiet from Monday.

NOAA has the solar flux index at 70-71 for the next seven days. The elevated Kp index over the weekend may cause maximum usable frequencies (MUFs) to decline, but next week should see the ionosphere settle back down to a Kp maximum of two, and normal HF conditions.

Maximum usable frequencies over a 3,000km path should remain similar to previous weeks. Expect 20 metres to be the DX band of choice, with some openings on 17m at times. There is always the chance of DX appearing on 15, 12 and even 10 metres, but these openings are likely to be short-lived and infrequent.

The good news is that next week we move into September, which should see a return to higher MUFs and better DX as the month progresses. This will also be a good time to work north-south paths, such as the UK to South Africa and South America.

VHF and up:

This period of more changeable weather is going to be hard to break and it looks like any weak ridges between the lows will be transient affairs. They are therefore unlikely to feature highly as tropo events, although the odd temporary lift is possible. The nature of unsettled weather, like the spell we’re in now, is such that the late summer sunshine can easily produce showers or even thunderstorms. These are very good for rain scatter and for most of the period from this weekend to next, a weather front or heavy showers may not be far away. So we’re entering another potentially productive period for the GHz rain scatter enthusiasts.

We are running out of time to mention sporadic E, so this may be the penultimate week. Clutching at straws perhaps, but there are some good jet streams in periods of unsettled weather and the next week will continue to look promising from a weather perspective, even though events are likely to be thin on the ground.

Moon declination is at a minimum this Sunday, but goes positive again on Friday, meaning Moon windows are getting longer. EME path losses are still rising, with apogee a week this Sunday. 144MHz sky temperatures are low all week, but the low Moon elevations mean that the noisy horizon will be in antenna beamwidths for the first part of the week.

Just one small meteor shower this week, the Aurigids, peaking on Monday with a zenith hourly rate of six. (rsgb.org)

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