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Propagation News – 4 July 2021

Well, NOAA certainly got the sunspot predictions wrong last week. It said that the solar flux index would be in the range 76 to 78 with a maximum Kp index of two. As it turned out, the SFI ended up way higher than this, peaking at 94 on Thursday. Active sunspot regions 2835 and 2836 ended up being bigger and more vigorous than predicted, pushing the sunspot number to a high of 53. This bodes well for the future and could mean that Solar Cycle 25 is now truly under way.

The CDXC group has reported 10m FT8 openings to China, Japan and South Korea, plus 10m and 12m openings to the Caribbean and South America.

Sporadic E has started to tail off a little as we enter July, and this is probably not helped by an increase in the Kp index to four on Wednesday night.

The major IT outage at the University of Massachusetts Lowell continues. This means there is still no ionosonde data on for foF2 graphs at the moment. Luckily, you can still access the live Chilton ionosonde data directly at, although you may need to register. A check on Thursday showed that the critical frequency mid-morning over the UK was around 4 to 4.5MHz, meaning a maximum useable frequency (MUF) over a 3,000km path of about 16.5MHz. Other than sporadic E openings, we can’t expect the MUF to rise much further until the autumn.

NOAA predicts the solar flux index will decline from around 92 to perhaps 85 next week, as regions 2835 and 2836 rotate off the visible face of the Sun. Geomagnetic conditions are predicted to remain relatively calm with the Kp index at two to three.
VHF and up:

Tropo opportunities have gradually diminished over the tail end of the week just gone. We had a super north-south duct up the East Coast on Wednesday evening, allowing a close-to 700km 10GHz tropo QSO between Keith, GM4ODA/P at IO99IV in Shetland and Neil, G4DBN in IO93NR, who’s almost at sea level on the Humber estuary.

We are now left with what is essentially a low pressure-driven weather pattern, with a small low crossing southern England early in the week. This will mean that periods of rain or heavy and possibly thundery showers are likely, so good for rain scatter on the GHz bands.

The main development will see low pressure over the British Isles or just to the west. The accompanying upper air pattern suggests a jet stream becoming established just to the south, over the near continent. This is a perfect location for supporting sporadic E paths into much of Europe, should other factors be in favour.

The jet stream strength also looks to be a bit stronger again, which is another good sign. Just keep in mind that the band will seem dead if you don’t call CQ! Mid-morning and late afternoon, to early evening, are going to be the most profitable times to do that.

Moon declination is positive and rising again so Moon visibility windows will lengthen. With apogee on Monday, path losses will be high.

There are no significant meteor showers until the end of the month, so continue to look around dawn for the best random meteor scatter opportunities. (

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