Propagation News – 1 May 2016

| April 29, 2016

It’s been another mixed week, with coronal holes dominating once again. The K-index, a measure of the disturbance to the Earth’s magnetic field due to incoming solar plasma, fluctuated all week, being as low as one and as high as four.

The solar flux index started the week at 82, but rose steadily to reach 94 by Friday. By then there were actually six sunspot regions visible on the sun, although some were so small they looked like dust on the lens.

Two small, but almost geo-effective, coronal holes could be seen in the Solar Dynamics Observatory‘s extreme ultra-violet image on Thursday, which suggest we may have unsettled conditions as you hear or read this report. NOAA predicts the solar flux index could rise to 95 by 3 May, although unsettled geomagnetic conditions will continue to affect propagation, especially on the first and fourth.

As we are now in May, sporadic-E will become prevalent on the higher HF bands, notably ten metres, but more about that later.

Otherwise, a look at an HF propagation coverage map from VOACAP Online shows May generally sees the start of the summer doldrums when maximum usable frequencies are generally lower during daylight hours, but remain higher at night.

VHF and up propagation news

We may start this weekend with a weak ridge of high pressure over southern Britain, which is potentially useful for some limited tropo, especially down to the south towards western France and northern Spain. Unfortunately, almost as soon as it happens, it will be gone and low pressure will be in control, so it’s more likely to be rain scatter on the GHz bands from large shower clouds that gives any enhancement locally.

On a more positive note, the sporadic-E season is now under way and current weather patterns are producing good jet streams in the right places over Europe. These are known to be helpful for sporadic-E and the sporadic-E maximum usable frequency has already reached more than 100MHz in the past week over the northern Balkans, and allowed UK stations to have six metre QSOs with Greece.

Sporadic-E is not an everyday thing, so check the beacons and clusters to follow any openings as it intensifies. Openings usually start as short skip on 10m, then up through 6m to 4m and perhaps even 2m. There are two main periods of activity from the UK, usually late morning and again late afternoon into early evening.

Moon declination is climbing this week and losses are falling as the moon comes in to perigee on Thursday. So this is a good week for EME with a daytime moon.

Category: GB2RS Propagation News