By Courtesy of the Propagation team
G3YLA JIM
G0KYA STEVE
G4BAO JOHN
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Jim Bacon G3YLA
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and Nick Henwood
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Propogation News
29th August 2025
HF
3
This week saw a change in HF propagation with a perceptible move towards more Autumnal conditions.
Ten and 12 metres have started opening up to the USA, at least on FT8. As we move into September this will improve further. Also, as we head towards the Autumnal Equinox we can expect better conditions on north-south paths, such as the UK to South Africa.
The week saw the solar flux index climb to 226 (on Thursday 28th) thanks to a host of sunspots, mainly in the Sun’s southern hemisphere.
Over the last seven days the Sun also provided us with 12 M-class solar flares. Any associated CMEs were not Earth-directed, so these had little effect and the Kp index stayed firmly at three or below. The latest NOAA/SWPC update lists only a 10 per-cent chance for a strong X-class solar flare.
FT8 continues to be the preferred HF mode (or so it seems), with stations in China, Japan, Indonesia and Cameroon making their way into UK logs on 12 metres.
The 10m band has also been humming with South America rolling in during late afternoon and early evening. This can only get better as we move into September and October.
Next week, NOAA predicts that the week will start with an SFI of 155 on Monday September 1st. This may be a little pessimistic, but we’ll see. It also predicts the SFI will drop off as the week progresses, ending the week at 125.
Geomagnetic conditions are forecast to be good for the first half of the week, but then decline from September 4th. Batten down the hatches as a Kp index of six is forecast for the 5th, with unsettled conditions lasting until the 10th. Check for auroral HF signals on the 5th, or even the possibility of visible aurora from the UK.
We recommend you get your HF DXing in early next week!
VHF and up
Last week saw some lovely late season Es on 6m and 4m including EA, I, and East into Ukraine. There was an opening to Brazil on the 24th that reached as far as East Anglia, but as usual stations on the South coast and West of the country had the best of the transatlantic QSOs.
This is the last bulletin in the nominal 2025 Sporadic-E season (May-August) and last week was a good reminder not to give up too soon with several CW/SSB paths showing up, particularly on 10m and 6m, but also a few reports on 4m.
The daily Es blogs on www.propquest.co.uk come to an end today (August 31st), but the site will continue to provide the maps as usual and notes on how to interpret the maps are there to help you. Thanks to all the Es operators who have submitted logs to the various clusters this year.
The change over to unsettled weather is now complete and we will see rain and thunderstorms to most areas from time to time. It’s a good period to check out rain scatter propagation if you are set up for the GHz bands.
The heavier rain is well-captured by the many online rain radar displays to help you track the most active scattering volumes, which move with the stronger winds quite high up in the atmosphere, and speeds of 30-60mph are common.
There is one note of contrast with the model evolution after midweek; one branch sticks with low pressure to the following weekend while another outcome tries to bring in a ridge of high pressure and a chance of Tropo propagation. If this turns out to be the actual evolution, it may prove useful for the 144MHz Trophy and Backpackers contest next weekend, but may not have arrived in time for the 144MHz UKAC on Tuesday.
The solar conditions are still providing some interest for auroral propagation, but with Kp less than 3, nothing of use radio-wise. Look for a Kp index increase beyond Kp=7 for that. The meteor activity continues to be ‘between showers’ so expect random activity, which suggests early mornings for checking out meteor scatter prospects.
Moon declination is negative, reaching a minimum on Monday 1st, so a week to check out the system rather than operate. With the Sun still high in the sky it’s easy to check system performance with Sun noise. Path losses start to fall after apogee on Friday the 29th. 144MHz sky noise is close to 3000K on Monday, dropping back to moderate on Wednesday.
G3YLA JIM
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G0KYA STEVE
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