Propagation News – 18 March 2018
The Commonwealth Contest, held last weekend, proved an ideal opportunity for UK stations to work some choice DX without the massive pile-ups you might get in other contests. Despite a large, elongated coronal hole on the Sun triggering a geomagnetic storm on the night of the ninth, there was still HF DX to be had, including Singapore, Mauritius, the Cayman Islands, Zambia and much more. Poor HF conditions meant that 20 metres was mainly the highest DX band of choice, but there was also plenty worked on 40 and 80m.
Geomagnetic disturbances continue to plague us. The equinox times are more prone to the solar wind coupling into the Earth’s magnetic field, due to something called the Russell-McPherron effect. Stronger magnetic storms tend to occur in March and September as the Bz interplanetary magnetic field is more likely to point southwards and couple with the Earth, resulting in auroral conditions. On a more positive note, with more and more daylight every week, 80m is now staying open longer into the evening, as is 20 metres.
Next week NOAA predicts the solar flux index will be around 70 to 72, but poor geomagnetic conditions with a predicted K-index of five are forecast for this weekend, and perhaps again around the 21st and 22nd. When geomagnetic conditions are more settled the maximum usable frequency over a 3,000km path often just exceeds 21MHz. But when the K-index rises this is often depressed to around 14MHz.
Don’t forget that March is a good month for working north-south paths on the higher bands, say 18 and 21MHz, while east-west paths can be better on 14MHz and below.
VHF and up
It’ll be windy and unsettled at first this weekend as a taste of winter returns, but there is some hope of a more traditional piece of VHF weather coming along as we move into the next week. The high pressure will begin to make its presence felt over the Highlands this weekend and then drift southwards, giving all areas of the country a chance to enjoy some tropo enhancements. By the end of next week low pressure will start to bring a return of unsettled weather. Other propagation modes are possible, but the high pressure developing means any snow showers may not have a great vertical extent, so might not be particularly suitable for microwave rain scatter.
We are getting closer to the new sporadic E season, but this usually makes its first appearance well to the south across the Mediterranean, say between Cyprus and the Balkans or from Spain to Italy, as we move into April. We are still in the annual period of no meteor showers until the return of the Lyrids on April 22nd. The best time for random meteor scatter QSOs is in the early mornings as the Earth is rotating in to the flux of random meteors.
The Moon’s declination goes positive today and losses will fall all week meaning improved EME conditions as the week progresses.
Category: GB2RS Propagation News
