Propagation News – 28 November 2021

| November 26, 2021

We had yet another week with low solar activity. The solar flux index started the week at 79 and by Thursday had only climbed to 83. Ideally, we want the SFI to be above 100 to guarantee good 10m openings. Geomagnetically, the Sun has been quiet with a maximum Kp index of three. On Thursday it was at one for most of the day. Propquest says that the MUF over a 3,000km path has exceeded 28MHz at times, but was stuck below 24.9MHz on Thursday. As a result, 10m sounded very quiet indeed.

This weekend is the CQWW CW contest, which is bound to generate some interest across the bands. Do take a look, especially on 21 and 28MHz, where we can expect some good DX at times, albeit somewhat fleetingly.

NOAA has the SFI pegged between 82 and 85 next week as well. There are signs of a possible new sunspot building on the STEREO Ahead spacecraft imagery, but we will have to wait and see.

The Kp index may rise to three this weekend, but next week looks quite settled with a Kp index of two forecast. There are coronal holes on the solar surface, but these are relatively small at the time of writing and look non threatening. As always, things can change quite quickly so don’t take out word for it. Keep an eye on for updates and for near real-time critical frequency figures.

VHF and up

The current unsettled spell of weather has curtailed any thoughts of Tropo for the period, which includes all of the coming week. This leaves rain scatter to discuss and these heavy showers, some wintry with hail or even thunder, may prove useful for the GHz bands. It is usually the case that showers can be quite vigorous early in the winter season, gaining their energy from the still relatively warm seas. This means that rain scatter paths will often involve showers running south or southeast over the North Sea or Irish Sea, which online weather radars or lightning displays can locate easily.

Other modes are available, such as meteor scatter or aurora and it’s well worth finding a good activity-logging website that displays these exotic paths to be there when the propagation is present. Most of the November meteor showers are past their peak, with the exception of the small November Orionids, active from the 13th of November to the 6th of  December, peaking on the 28th of November.

The big Geminids meteor shower with a ZHR of 120+ is getting closer. It usually starts to build up from the beginning of December so watch out for improving meteor scatter conditions. Remember that the period around dawn is the best for random, ie non-shower, meteor scatter conditions.

For EME enthusiasts, Moon declination is still positive until Tuesday and reaches perigee on Saturday. Expect shortening Moon windows and lower peak elevations, but decreasing path losses as the week progresses. Next Saturday morning the Moon and Sun are close in the sky so expect high sky temperatures due to Sun noise, with levels reaching over 3,000 Kelvin at 144MHz on Sunday.

Category: GB2RS Propagation News