Propagation News – 10 December 2017

Last week, the effects of the high-speed solar wind from another coronal hole saw the K-index climb to five on Tuesday and remain relatively high throughout Wednesday and Thursday. The ionosphere took a hit and daytime maximum usable frequencies struggled to exceed 18MHz at times. By Thursday, conditions were starting to improve a little, but the HF bands were still noisy with a distinct lack of signals.

The solar disk also remained fairly unblemished by sunspots, other than one very tiny group of three that saw the solar flux index climb, if that is the right word, to 68. This will most likely be the trend for the next 18 months or so as we experience the end of solar cycle 24.

Daytime critical frequencies have been around five to six megahertz, which means 60 and 80 metres remain the best bands for UK-wide short skip in daylight. Night-time critical frequencies of around three megahertz mean 80m is largely closed to short skip, although both it and 40 metres are potentially open to longer distances.

This weekend, another coronal hole is rotating into an Earth-facing position and NOAA predicts we may have disturbed geomagnetic conditions from Monday the 11th through to Wednesday the 13th. Conditions should then be more settled through to next weekend.

The solar flux index is predicted to continue to hover around the 68-70 mark and, with such a poor prognosis for HF propagation, it might be worth concentrating on night-time DX, or looking at using more efficient data modes, such as PSK or FT8 on the 20 and 30 metre bands during daylight.

VHF and up

This week, the nights of the 13th and 14th see the peak of the Geminids, one of the largest meteor showers of the year. The Zenithal Hourly Rate (ZHR), is an idealised number for the visually-observed meteors seen under a moonless sky with the radiant at the zenith. There will be many more radio meteor reflections observed than this number. The Geminids has a ZHR rate of 120, so look for plenty of good, strong meteor bursts on the lower VHF bands.

As well as the usual digimodes, SSB and CW QSOs can often be made in this shower, if you get your operating technique nice and slick. There is no moonlight on Wednesday night, so, if the skies are clear, go outside and take a look for bright meteors.

We are in a cold northerly weather pattern for this week and with minor troughs running south and small lows developing; this type of weather is very poor for tropo. That leaves us just a hope for some rain/snow scatter on the gigahertz bands from some of the heavy wintry showers, which will be fairly commonplace near the coasts. More organised areas of rain and snow may affect some areas during the week. As usual, use the various radar visualisation tools online to track the precipitation.

Moon declination goes negative on Monday night and losses are rising as the Moon moves away. Due to this, EME opportunities will be shorter and signals lower.

Category: GB2RS Propagation News