venerdì 31 luglio 2020

Propagation News – 2 August 2020

The Sun showed signs of coming back to life this week with not one, but two, sunspot groups. The sunspot number climbed to 22, representing two spots in two separate groups, and the solar flux index rose to 73. This wasn’t really enough to make much of a difference to HF propagation though, but it is a step in the right direction. The Kp index was pegged pretty much at one or two due to a lack of coronal hole activity.

Propagation-wise, we continued to have a good run of sporadic E, with openings to the USA and Canada on 10m SSB and FT8, and China was reported on SSB in last weekend’s IOTA contest. Even Nand, VU2NKS, in India has been reported in the UK via 10m FT8. Next week NOAA predicts that the solar flux index will decline from 72 down to 68 as the two sunspots rotate out of view. The Kp index should remain low all week as well due to a lack of coronal hole activity. Propagation will remain at seasonal lows as we enter August, with daytime F2 maximum usable frequencies grazing 17-18MHz, and with sporadic E bringing openings up to 30MHz and beyond. Night-time maximum usable frequencies are likely to exceed 10MHz over 3,000km paths, but keep an eye on for the odd surprise. We can’t really expect F2 layer openings to improve until September, so make the most of the sporadic E openings for now.

VHF and up:

The next week or so looks to be a mix of brief spells when high pressure might present us with some tropo, as seen just recently at the end of the last week, due to a temporary high over the near continent. The longer range part of the forecast also picks up another high at the end of the coming week, although for both these highs, the main areas of enhanced tropo are for central and southern Britain across the Channel and North Sea, into the continent and Baltic region.

The period in between the two high-pressure ‘bookends’ is occupied by low-pressure systems with fronts and showery troughs adding a good chance of rain scatter again on the GHz bands. The summer months are particularly good for strong thundery shower-cloud development with plenty of high-intensity rainfall or hail.

Sporadic E has performed fairly well in the last week, particularly for FT8, but with a smattering of more traditional modes. The general advice still holds—check the bands mid-morning, late afternoon and early evening for signs of sporadic E. It’s never too late for sporadic E, until maybe the end of the first week in September, so it’s still well worth a look.

The Moon is at minimum declination this Sunday so there will be very low peak Moon elevations and short visibility windows early in the week. This means that, despite 144MHz sky noise being low, the man-made noise from the horizon will be in the main beam of all but the largest antennas.

There are no significant meteor showers this week. (