Propagation News – 11 December 2022

| December 9, 2022

There’s an old Chinese curse that says: “May you live in interesting times”. Well, the last week has been very interesting from an HF propagation perspective!

The solar flux index increased from 111 on 30 November, to 148 on Thursday, the 8th. During that time, we had more than 50 C-class solar flares and two M-class flares, while the Kp index ranged from one to five. So, it’s been a bit like having all four seasons in one week!

HF propagation has varied dramatically as a result, with round-the-world echoes and spotlight propagation being very prevalent at times. Spotlight propagation is defined as a small geographic area that is favoured with good propagation at any given time.

The Norfolk Amateur Radio Club operated G6ZZ for 48 hours as part of the transatlantic centenary celebrations and worked more than 1,500 stations. Station manager Chris, G0DWV reports his highlights as: “Hearing my own echo as the signal went around the world on several occasions, being called by VK, Australia, and ZL, New Zealand, at 5/9+30dB with no one else on the band. And hearing echoes that made it impossible to understand the caller’s voice.”

At the moment, it seems like it would be easy to dismiss an HF band as being closed, when it could be wide open half an hour later.

The Sun is currently peppered with spots of all sizes. The US Air Force predicts that the good conditions could continue for a few days yet, with the solar flux index falling from 150 on Sunday to 110 by the end of the week.

Calm geomagnetic conditions may continue, and there are currently no coronal holes in view. But please note that it only takes a single coronal mass ejection to spoil things.

And don’t forget that the low bands come into their own in winter as well. This is a good time to look for DX on 160, 80 and 40 metres, especially in the late afternoon, after dark and at sunrise.

VHF and up

This week’s VHF propagation highlight is the Geminids meteor shower. This is predicted to reach a broad peak over several days on either side of 1300UTC on 14 December.

The Geminids zenithal hourly record has reached 140 to 150 in all recent years so expect a good one with SSB QSOs possible for the better-equipped stations using good operating techniques, and the chance of 70cm digimode QSOs as well. The broad peak has a habit of declining quite quickly once it’s over.

In this present turn to cold winter conditions, prospects for high pressure and tropo are looking limited, apart from a weak ridge over northern Britain. Although even this is not a strong player.

Current weather conditions may appeal to the experimentally minded. Intense cold and snow-covered ground can produce strong shallow surface temperature inversions, so there may be interesting tests to be done in some parts of the country. Also, watch out for snow scatter on the high GHz bands if you see snowstorms around.

The solar-driven conditions mentioned in the previous section suggest that further possibilities exist for auroral propagation, given a high Kp index.

The dearth of sporadic E during the autumn months usually has a brief respite around this time of the year from mid-December to mid-January. It’s very random but follow the usual summer routine of checking the clusters and maps to select the right directions. Although these isolated events can occur at the usual afternoon or evening times for Es, they can and do crop up in the morning and around the middle of the day.

Moon declination is positive but decreasing this week so Moon windows will shorten and zenith angles decrease. Path losses are at their highest with the Moon at apogee on Sunday night. 144MHz sky noise is low all week.

Category: GB2RS Propagation News