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Propagation News – 19 September 2021

After last week’s very active Sun, we have had a quieter week with little solar activity. As of Thursday, there were zero sunspots and the solar flux index had declined to 75, pretty much as predicted. The upside is that the Sun has been quiet geomagnetically with a maximum Kp index of three over the past week. This means the ionosphere has not been adversely affected.

HF conditions have been adequate rather than exceptional, with FT8 F2-layer openings on 10 metres as well as some late-season sporadic E. Brazil has been logged in the late afternoons on 10m FT8, as have a few other stations from the Caribbean and South America. We haven’t seen much of the long-awaited autumnal transatlantic DX on 10 metres, but it is still early days. We may not see this until later in the month, or even early October.

At the moment it isn’t looking too good for next week either. NOAA predicts the SFI will be in the range 76 to 78. This could, of course, change if we have a sudden outburst of sunspots. Geomagnetically, NOAA predicts more of the same with the Kp index at two to three. Propquest shows that the predicted maximum usable frequency over a 3,000km path is likely to just touch the lower end of 21MHz at times.

VHF and up:

The continuation of the mixed weak tropo and rain scatter modes seems to be the way to go during the period to next weekend. At the moment the primary tropo period comes along for the first half of next week, before being eroded from the west as Atlantic fronts move in. The preferred tropo directions are probably east across the North Sea and south into northern France. The other modes such as meteor scatter and aurora and of course, that most reliable of DX modes, aircraft scatter, are always worth checking out.

Now international air travel is getting frequent again, the dip in aircraft scatter opportunities that we had at the height of the pandemic should be reducing, so check for the latest on VHF and up beacons and monitor them to see some interesting propagation, and set up some skeds on VHF and up via the chat.

Look on to download an excellent aircraft scatter path prediction program from Frank, DL2ALF.

No meteor showers this week, and random meteor activity will be declining from the August/September peak, but keep checking in the early morning for the best random meteor scatter conditions.

Time to put the EME system back in the dish for this month as we return to positive Moon declination on Tuesday. Losses are still low but increasing this week. The Moon is up from early evening to the early hours. (

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