By Courtesy of the Propagation team
G3YLA JIM
G0KYA STEVE
G4BAO JOHN
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Jim Bacon G3YLA
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Propogation News
3rd May 2024
HF
3
What a strange week we've had. With the solar flux index in the range 167, falling to 130, conditions should have been reasonable. But the Kp index hit four and even 5.33 on the evening of Friday 26 April, which meant propagation on Saturday the 27th was truly dire.
Stations taking part in International Marconi Day on the 27th found 40m only open to long skip in the morning. This was due to the critical frequency being below 5MHz. The predicted MUF over a 3,000km path fluctuated between 15MHz and 19MHz for the whole day, which meant only 14MHz was open reliably. As a result, QSOs were hard to come by and many stations reported that it was slow going with virtually no signals from outside of Europe.
So what happened? It was a combination of factors - the increased Kp index due to a fast solar wind took its toll. And we are now moving to a summer ionosphere, where chemical changes make it harder to ionise. This will mean we should see MUFs dropping as the season progresses, at least during the day. Nighttime MUFs will be higher than in winter.
So it may be that the glory days of 28MHz F2-layer propagation are on hold until Autumn, with only short-skip Sporadic E on 10 metres to keep us entertained.
F2-layer propagation is still available on the higher HF bands, but it may be patchy.
International Marconi Day station GB0CMS in Caister, Norfolk, reported that their 20m signals were picked up by a reverse beacon network skimmer in Utah, despite not working anyone outside of Europe. Meanwhile, Laurie G3UML was quite surprised to work YJ0CA on Vanuatu (15m SSB), 3D2CCC on Conway Reef (20m CW) and JD1BMH in Japan (15m CW) on the morning of the 2nd.
Next week NOAA predicts the SFI will be in the range 125, rising to 175 as the week progresses. Geomagnetic conditions are dependent on coronal mass ejections. We have had eight M-class solar flares in the past three days, and a Kp index of five on Thursday 2nd, which doesn’t bode well for next week. So keep an eye on solarham.com for current conditions and look for the best HF propagation if the Kp index is low for a day or two.
VHF and up
The weather pattern remains very unsettled for the whole period with areas of low pressure edging north across the UK from the continent.
There will be a risk of thundery weather at times with locally heavy rainfall, which will be good for rain scatter on the GigaHertz bands. Tropo looks to be hard to find as we end the current week dominated by low-pressure systems, but there are signs of high pressure returning after mid-week, but only temporarily.
This could produce some Tropo paths, especially across surrounding seas like the Irish Sea, English Channel and North Sea.
The nominal summer season of Sporadic-E is upon us and, from May to early September, daily blogs will be provided on the Propquest.co.uk website highlighting the possible Es links to the position of the jet streams shown on the upper air charts.
It’s well worthwhile getting into the habit of regularly checking the DX clusters and activity maps, since the early season is usually characterised by a complex jet stream pattern with multiple potential locations for Es.
Time-wise, it eventually settles into a more traditional behaviour with activity often in two phases, one in the morning and the second in late afternoon, early evening.
As this is being presented the Eta Aquariids meteor shower should be peaking. Unfortunately, the best viewing for the shower, which is part of the debris from Halley’s comet, will be in the southern hemisphere.
Nevertheless, this is expected to be one of the best showers this century. For those viewing the shower, a waning Moon means that light levels should be low, making for ideal visual sighting.
For EME, the Moon will be waning all week with the new Moon around the May 8th. The Moon will be rising in the sky throughout the week, with zero declination (Moon crossing the ecliptic) on the May 5th and peaking at its highest in the sky on Saturday May 11th.
The lowest additional path loss occurs around the 5th and 6th, but high Sun noise, with the Moon close to the Sun at new Moon, occurs shortly afterwards. Later in the week, as the Sun 'leaves' the Moon behind, noise levels, at least on the higher bands will fall to around normal
G3YLA JIM
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