venerdì 18 novembre 2016

Propagation News – 20 November 2016

Last week, the solar flux index hovered around the 80 mark, with average sunspot counts reaching their lowest level in five years. With sunspot minimum predicted to be some time in 2018 or 2019, this is a taste of what we can expect for the time being.
But it wasn’t all bad news, as geomagnetic conditions were quite settled midweek with the planetary K index at one or two. As a result the HF bands were alive. Malcolm, G3PDH reports hearing as far as Arizona on 20 metres and the Chilton Digisonde suggested openings on 21MHz were possible over a 3,000km path.

Unfortunately, coronal hole activity on the Sun may, once again, result in unsettled conditions this weekend, the 19th and 20th. Expect the K index to rise and maximum usable frequencies to decline, although we can sometimes get a pre-auroral enhancement as the solar plasma first hits.

NOAA predicts that the solar flux index will continue in the range 75-80, but the K index will likely be in the range four to seven at times. So long-range DX may be impacted adversely, especially on routes over the North Pole.

Geomagnetic conditions for the following week’s CQ Worldwide contest are also predicted to be unsettled, although perhaps not as bad as this weekend. Trying to be positive, early December is looking better.

There would seem to be another week of low pressure in store for us and sadly, that means a limited chance of Tropo developing. For the latter part of the week, there is an indication from one of the models for high pressure to move in over the southern half of Britain. This represents a limited chance for Tropo later in the week, but another weather model refuses to select high pressure to end the week, so is not to be trusted this far in advance.

There will be some heavy rain and showers at times, so always a chance of some rain scatter on the gigahertz bands, especially around the coastal fringes where the showers will be heavier.

Last Monday’s so-called Supermoon, the closest perigee since the 1940s, produced improved EME signals, especially on the GHz bands, due to the low path losses. In the coming week losses are moderate, but increasing. Moon declination goes negative on Thursday and windows shorten, but there are still plenty of EME opportunities to be had.

For meteor scatter enthusiasts, the Leonids are all but over but we now have the major Geminids shower to look forward to in a few weeks time.