Propagation News – 5 April 2015

First, as we are now into April, please ensure that you are using the correct smoothed sunspot number of 61 with your VOACAP-based propagation programs.

Over the past week the solar flux index continued in the range 120-130. The prediction for the coming week is for ‘more of the same’, with the SFI around 135-145. This may look a little optimistic as the current image of the Sun shows no new sunspots appearing around the western limb. However, as recent experience has shown us, new sunspots can pop out of nowhere so time will tell.

Geomagnetic conditions are predicted to be settled, which could bring good HF conditions.

As we move into April, HF conditions decline a little on the upper bands as we move towards summer. For example, on the path between the UK and New York, the optimum working frequency is now around 18MHz, whereas last month it was 21MHz. But on more southerly paths, such as the UK to Rio de Janeiro in Brazil, the optimum working frequency continues to be 24MHz.

The end of the month should see the return of Sporadic-E conditions, predominantly on 28MHz and 50MHz, although Sporadic-E affects all HF bands from 14MHz upwards.

VHF and up propagation news

At long last there are indications of a prolonged period of high pressure over the British Isles, which will be great news for VHF and UHF folk, as well as good news for those having the Easter week off as holiday. The area of high pressure will probably produce sustained lift conditions after a few days, as a temperature inversion becomes established and produces the ducting conditions necessary for VHF and UHF openings.

As we said earlier, we are also near the start of the Sporadic-E season, especially in southern Europe and on the upper HF/lower VHF bands like 10m, and 6m, so it is always worth checking the beacons. This rule also applies for VHF/UHF tropo. Beacons are important tools, so thank you to the beacon keepers for a great resource.

For EME, the Moon declination decreases to a minimum on the 10th, with sky noise and degradation increasing during the coming week. There are no major meteor showers due in the coming week.

Category: GB2RS Propagation News