Severe geomagnetic storm, May 10-11, 2024.

Over the years, being lucky to live in an area not yet terribly blighted by light pollution, I've seen a number of aurorae from Anglesey. Some have been quite impressive, notably the display of March 2014.

March 2014 aurora seen from Anglesey. This was the strongest I'd seen since 8-9 November, 1991.

 

I've also been lucky to have a long relationship with Iceland, and was lucky to witness a full substorm display in September, 2011; all the days were rainy, but almost all the nights of the week were clear!

 

Major auroral substorm seen from southern Iceland, 26/09/2011.

But I hadn't expected to see an aurora from Wales that matched and even exceeded what I had seen in Iceland, which is what happened on the evening of May 10-11. A huge additional piece of luck was that the Welsh skies were almost completely clear of cloud so that we could see what was going on above our heads!

The CMEs that gave rise to this event were well-forecast and were predicted to be so strong in impact as to make the earlier part of news headlines on BBC Radio 4 the preceding day.

Spot group 3664 gave rise to three powerful CMEs that gave rise to strong aurorae. An area of the group had a row of umbral footprints that were very similar to those recorded at the time of the Carrington event of 1859.

 

Carrington Event, 1859 spot group.

A quick listen at home to 50MHz, using only a 30m delta loop from a relatively poor environment, revealed that there were already strong auroral SSB signals to be heard in the afternoon of May 10, as heard in the brief video, below:

 

Suitably alerted, I headed out with my ageing FT-450 rig under my arms before it got dark to my field shack, where I have a modest but very effective 3-element Innovantennas OWL Yagi. I do have a particular interest in auroral SSB, where a wider, rather than a narrower beamwidth is beneficial. Everything is solar-charged battery, with about 40W PEP.

Very disturbed indeed!

As it slowly darkened, it became clear that the aurora was present in the north-east. I was making SSB contacts beaming in this direction with stations in England from around 23:00UT. Within the next few minutes, I could hear strong French stations coming in from the NE, and made contacts with two of them.

Auroral SSB QSOs for the event. I was too busy looking to hunt for more QSOs!

 

Being quite late in the evening, there weren't that many different stations to make contact with. It was also the case that the aurora was extending so far to the south that signals I normally hear by aurora - Scotland and the Faroes, for example, were not heard very often, though as time went by and the aurora swept west, those areas were heard. Sadly, the geometry was such that I could hear the Faroes but not, this time, make a QSO with them. In the rush, I hadn't taken a mobile phone to record anything, but that was corrected the following afternoon, when conditions remained very elevated.

Auroral rays reach down from overhead, revealing my 3-ele OWL Yagi for 50MHz, beaming to the NE, in silhouette. The image was taken to have close fidelity to the naked-eye view.

 

In the end, the aurora was so extensive, strong, colourful and dynamic (pinks and reds were especially noteworthy) that radio took a firm back seat to simply gazing up in awe. At peak intensity, which lasted for quite a while, the landscape was clearly visible for miles around under the auroral light and it was even possible to read modestly-large text. My neck eventually came to hurt from craning to look overhead at the incoming rays.

The aurora at around 23:15UT, May 10 2024, looking east. Again, the image reflects closely the naked-eye experience.

Well into the 11th of May, conditions remained strong enough to sustain auroral QSOs, though I didn't make much of an effort, being very satisfied indeed in having made the extraordinary links the following day with France by auroral reflection. From home, FT8 signals, which could be decoded on the 10th, were so spread out on the 11th that none of them were being decoded.

FT8 signals at 50MHz, hopelessly spread out by aurora on May 11th. The transmitted bandwidth for FT8 is indicated by the vertical red tramlines!

Quite an event!

 

Chinese Mini-Whip: important discovery.

A recent comparison, which I highlighted at the time was only a quick test done in poor weather and needed more work, resulted in my concluding that the generic Chinese mini-whip system has some broadband noise. This noise was absent when using the PA0RDT mini-whip at the same time.

My generic Chinese mini-whip system.

 

I realised during an early morning hours session of reception today that the Chinese whip does not in fact suffer from broadband noise as a system. The noise, in fact, is transmitted by a mouse cable connected to my 1 year-old laptop. 

In addition to mouse RFI, it became apparent that touching the laptop, notably the mousepad, also caused noise which was in fact considerably stronger than that transmitted by the physical mouse and its cable.

The level of the noise is not high, but is certainly of a magnitude where it would mask weaker NDB (or other) signals, and is thus a significant issue.

On closer examination, it's clear that the PA0RDT whip is also affected by the RFI, as the following waterfall demonstrates:

PA0RDT whip with wired mouse connected.

Here's what the Chinese whip's waterfall looks like when listening at typical NDB frequencies with the wired mouse connected:

Chinese mini-whip with wired mouse connected at the laptop. Note the constantly-repeating RFI.

 And this is what the waterfall looks like when the mouse is not connected to the laptop; I've tried to display the waterfall as close as possible to the previous waterfall:

Chinese mini-whip with the mouse disconnected. Note the lack of repeating RFI now.

So that's cleared up: both whips are affected, to much the same degree, by RFI from the computer and its wired mouse. How about the signals?  PA0RDT himself told me recently that he considers the signal-to-noise ratio reading to be a more meaningful measure of a whip's performance than, say, an 'S' meter reading, noting that a SNR reading is more difficult to obtain, given QSB and so on. 

I looked at some low frequency commercial signals and one time signal, and the results are as follows:

189kHz,RÚV1, Iceland (peak signal strength and peak SNR)

Chinese: -78.5dBm, +12.1dB SNR

PA0RDT: -81.5dBm, +9.3dB SNR

198kHz, BBC Radio 4, UK

Chinese: -45.6dBm, +47.1dB SNR

PA0RDT: -39.7dBm, +47.3dB SNR

225kHz, Polskie Radio

Chinese: -72.4dBm, +17.2dB SNR

PA0RDT: -67dBm, +14.9dB SNR

252kHz, Radio Algérienne Ch. 3

Chinese: -60.5dBm, +30.6dB SNR

PA0RDT: -56.3dBm, +29.1dB SNR

60kHz, time signal, UK

Chinese: -52dBm, +51.7dB SNR

PA0RDT: -44.8dBm, +51.9dB SNR

Other than in the case of RÚV1 (Iceland), the PA0RDT yields significantly stronger signal strength than the Chinese unit, by a mean of 5.7dBm. In terms of SNR, the Chinese unit comes in at a mean of 1.24dB better than the PA0RDT (maximum of +2.8dB, minimum of -0.2dB SNR). The SNR difference is not significant and is likely to disappear if a longer test were conducted and this might also prove true with the signal strength. The two units can reasonably said to be equivalent, in my view.

I've also listened to the signals by ear and compared their quality. Whilst signal strength is comparable, there is very definitely more noise to the Chinese whip when listening, for example, to voice (plain AM mode) transmitted by Polskie Radio.

Here's a short clip from the Chinese unit:

And compare that with the output from the PA0RDT unit:

The next step will be to look at some real-world use of the signals from both units (without a wired mouse connected to the laptop) and see whether very weak NDBs are detected more clearly by one of the units. That will, of course, take some time to complete.