Propagation News – 8 April 2023

Solar activity declined this past week with the Sun looking distinctly spotless, other than active region 3270.

In fact, this has even prompted some amateurs to question whether we are now past solar maximum for this cycle. Rest assured, we shouldn’t be, as it is pretty common for cycles to ebb and flow as they develop.

Having said that, half of the Sun’s face is currently spotless, and NOAA predicts that the solar flux index will be in the range of 110 to 130 next week.

Geomagnetically, things have been reasonably settled with the Kp index reaching a maximum of 4.67 over the past seven days. NOAA predicts that it could rise to four on the 10 and 11 April but will otherwise stay pretty much as it is in the range of two to three. This may be due to a coronal hole that is currently making its way across the Sun’s face in a near-equatorial position.

However, we may not have seen the last of the activity from active region 3270, which has increased in both size and magnetic complexity during the past 48 hours and could soon produce a moderate M-Flare. But, if you are reading or hearing this on Sunday, the region will be moving out of sight and is therefore no longer a threat.

Daytime F2 critical frequencies at midday remain around 9 to 10MHz giving a maximum useable frequency, over a 3,000km path, of just over 28MHz.

If 10m isn’t doing it for you we suggest moving down to 12 or 15m. Night-time F-layer critical frequencies are around 3 to 5MHz meaning MUFs over 3,000km are below 14MHz, leaving 3.5, 7 and 10MHz as the best bets for nocturnal DX.

VHF and up

The current spell of high-pressure weather with enhanced Tropo, which turned up in time for the 2m UK Activity Contest on the 4 April, is looking a bit vulnerable as active weather fronts come in from the Atlantic.

We are likely to have a brief change to unsettled conditions weather-wise before the start of the Easter weekend and again see some rain scatter opportunities on the GHz bands.

Scandinavian highs are often long-lasting at this time of the year and this high will regain control by Good Friday and should dominate over the UK during the Easter weekend to give some useful tropo possibilities again.

However, quite early next week a new powerful Atlantic jet stream pushes into northern France and will bring a return of unsettled weather and perhaps more rain scatter.

The Sporadic-E season is approaching and the higher HF bands like 10m can show good examples of Es, even during the second half of April, so a good chance to get into the habit of checking your ‘go to’ list of 10m beacons as recently updated by Steve, G0KYA, on the propagation section of the RSGB website.

The other defaults of auroral propagation have had a good run recently and random meteor scatter could also prove fruitful as we are soon ending the early year ‘drought’ of meteor showers with the arrival of the Lyrids later this month.

For EME operators, Moon declination is negative and falling, reaching its minimum next Wednesday. Moon time will be limited to low-elevation passes, but with low path losses as we approach perigee on the 16 April.

144MHz sky noise is increasing to a high of more than 2,000 Kelvin next Wednesday before falling back to the mid-200s the following Sunday.

Category: GB2RS Propagation News