Propagation News – 24 January 2016

We’ve had yet another week with unsettled geomagnetic conditions. This time the Kp index hit five on Wednesday, and even six on Thursday, caused by a plasma emission from the Sun with a prolonged southward-facing Bz field. This was a shame as the field had been very settled on Monday, with a Kp index of zero, which usually bodes well for good HF conditions.

On Monday the critical F2 layer frequency, as measured by the Chilton ionosonde, hit 6.8MHz at noon, giving a predicted maximum usable frequency of about 21MHz.

By Wednesday it was 7.6MHz, giving a MUF of about 25MHz over 3,000km. This shows that, perversely, a higher K index can sometimes result in better conditions as the initial onset of solar plasma can cause a positive phase with better maximum useable frequencies, before the subsequent negative phase with depressed MUFs, noisy bands and auroral conditions.

The moral of the story is that the best thing to do is monitor the HF bands as often as you can, as you never really know what you might hear.

The forecast for the next week is more of the same, with a further high risk of unsettled geomagnetic conditions at times, especially on the 28th and 29th.

VHF and up propagation news

The edge of a high pressure system sits well to the East over the continent, so stations in the South and East of the country could get some enhanced conditions this week.

The second half of the week looks the best, with the F5LEN tropo maps showing a long narrow finger of enhancement over Southern England, into the Low Countries and the Southern Baltic. This could link up with the Azores high, providing slightly-enhanced conditions into Western France, Spain and Portugal. Otherwise, the bulk of the country offers windier weather with low pressure and frontal rain bands, with not much tropo on offer for VHF and UHF. However, some active weather fronts could introduce the prospect of some rain scatter on the GHz bands.

We are now in the year’s quiet period for meteor activity, extending from early January until the Lyrids shower at the end of April, so it’s back to early mornings waiting patiently for the random meteors to provide fleeting low VHF DX opportunities.

Moon declination is falling and goes negative on Thursday and, with apogee next Saturday, path losses will continue to increase throughout the week.

Category: GB2RS Propagation News