Propagation News – 22 August 2021

We had another week of low sunspot numbers, but generally settled geomagnetic conditions. The solar flux index generally stayed in the range of 73-75, which is nothing to get too excited about. The Kp index hit a maximum of three, but was more often at zero or one.

Maximum usable frequencies over a 3,000km path have struggled to exceed 18MHz during daylight hours and 14MHz has probably been more usable. Thirty metres, and sometimes 20 metres, have remained open long after dark, but we are seeing those bands closing earlier as we leave Summer and head towards Autumn. But this does mean that we are also heading for an upturn in ionospheric propagation as the chemical make-up of the ionosphere changes from molecular to atomic components, which are easier to ionise.

Next week, NOAA predicts more of the same, with a solar flux index in the range 72-74. It also predicts a rise in the Kp index to four on Tuesday the 24th, which could see MUFs decline. This may be due to a high-speed stream from a coronal hole, stretching down towards the solar equator and currently rotating into an Earth-facing position.

It’s the North American SSB QSO party this weekend, so perhaps a good opportunity for a trans-Atlantic phone contact. Again, 20 metres would be best during daylight hours, with an occasional opening on 15 metres.

VHF and up

Last week’s spell of indifferent summer weather partially supported Tropo conditions due to a weak ridge close to southern areas, but it remained more unsettled in the northwest. This Tropo saw a few stations in Southern England managing to launch signals into the almost ever-present Tropo ducting down to the Canaries caused by the Azores High phenomenon. Even some lucky stations east of the Meridian in JO02 square worked the 3,000km or so path to the Canaries and Madeira, EA8 and CT3 respectively, on 144MHz FT8. This is very rare on Tropo alone and usually is the privilege of stations much further south and west.

Early in the coming week a high-pressure area is signalled to return to northern areas initially, with improving Tropo prospects soon extending to the whole country in the early part of next week. Some models suggest the return of low pressure towards the end of the week, with some rain scatter to be had from this on the microwave bands.

There have been a few Sporadic-E examples continuing into the second half of August and, although becoming harder to find now, it is still worth checking the clusters and beacons. Last week, some activity on 10m even extended well past midnight.

We are still close to the broad-peaked Perseids meteor shower, so continue to monitor for improved meteor scatter conditions. The shower radiant might still enhance the usual peak of random meteors around dawn.

Moon declination goes positive again on Wednesday so we’ll see lengthening Moon windows and higher peak Moon elevation as the week progresses. Path losses will rise steadily as the Moon goes out to apogee, its farthest point from Earth, a week on Monday, the 30th.

Category: GB2RS Propagation News