Propagation News – 15 March 2020

A new sunspot group, numbered AR 2758 and from upcoming Solar Cycle 25, appeared this week. The region was located in the Sun’s southeast quadrant, but had faded away by Thursday the 12th. This was the first numbered sunspot region to appear in over a month as solar activity continues on at very low levels.

Overall, the solar flux index remained at 70-71 with the geomagnetic Kp index being in the range zero to two, reflecting calm conditions.

Wednesday’s RSGB 80m CW Club Championship contest proved just how inactive the Sun is at the moment. The contest started quite well, but soon everyone was struggling to make contacts as the critical frequency dropped below 3MHz as measured by the Chilton ionosonde.

As a result, many contesters had to make do with QSOs with the Netherlands, Sweden and Germany as their higher-angle skip for local contacts failed to return to Earth.

Daytime critical frequencies have often struggled to exceed 5MHz in the morning and 5.5MHz in the afternoon, meaning 40m remains unsuitable for NVIS-type communications.
On DX, maximum usable frequencies over a 3,000km path have occasionally exceeded 21MHz in the daytime, but 18MHz has been more reliable.

Next week, NOAA has the solar flux index pegged at 70-72 with quiet geomagnetic conditions, apart from March 19 when the Kp index is forecast to rise to four, possibly due to a high-speed solar wind stream from a returning coronal hole.

VHF and up

At last there is a signal in the forecast models for the return of some high pressure weather. After a prolonged period of windy and unsettled conditions, the first signs of a building high will come after this weekend as a ridge builds towards the southern UK from the Azores region.

Eventually a new high, building in colder air over northern Britain, will probably take over in the second half of the week. Either way, it’s time to consider the chance of some Tropo conditions later in the week, which will make a welcome change.

It’s worth noting that the spring equinox is prime time for the possibility of aurora, so keep an eye out for high K indices as a ‘heads up’ for possible DX on the VHF bands.

The Moon’s declination is at its most negative on Tuesday, so the Moon only reaches 13 degrees above the horizon. This means that ground noise is in the antenna lobes for much of the Moon window.

Path losses are increasing throughout the week and 144MHz sky noise is very high for the next few days, so a poor week for EME.

With no major meteor showers due until the Lyrids at the end of April now, just keep looking for random meteor scatter QSOs around dawn.

And that’s all from the propagation team this week.

Category: GB2RS Propagation News