While I was activating W0C/FR-081, Button Rock Mountain, yesterday, 9 May 2023, I experienced some very strong noise at about 1845 UT.
I first heard this noise while calling CQ on CW at 18.093 MHz, at about 1840. Since the summit I was on is over a mile from development, well into unpopulated National Forest, with the nearest power line over a mile away, I was very surprised to hear it!
I’ve activated this summit many times, and I regard it as one of the more quiet local peaks with reasonable hiking access. The closest ungated road is one mile away, and the forest roads were still gated. There were no motor vehicles near my area.
This noise was unmodulated, without a hint of AC, or any other tone, and it varied and increased in intensity over a period of several minutes. While there were a few clouds in the area, the weather was stable, and there were no cumulus clouds close enough to cause corona.
This noise was LOUD. When the S-Meter on my KX2 hit S8 on 18.093, at about 1846 UT, I knew something important was happening. I got up, looked around, checked the sky, and there was nothing odd. I made notes in my log.
On the KX2 I jumped from band to band, without even peaking my tuner, and the noise was loud and distinctly similar on all the bands I checked - 17, 15, 12, and 10M. This was several S units above background, for sure. The noise continued for several more minutes.
No one answered my CQ’s at 18.093, which was strange, although I was first spotted by the RBN Hole at 1841 UT. After about 1850 UT, the noise dropped slowly. Then I called CQ at 21.063 MHz, mostly to see if I could get spotted. I was spotted by the RBN Hole at 1854 UT. However, after several minutes, no one responded to my CQ on 15M. The noise level was near normal after I quit calling.
I decided to take a break and walk around, and I was thinking about packing up and leaving. Instead I decided to call CQ on 10.113 MHz, with the hope of catching a few chasers or activators I might have missed. I was spotted on 10.113 MHz at 1910 UT, and N1CLC called me S2S from AZ a few minutes later - all was well!
The bands recovered nicely, and I went on to have a nice run of activators and chasers on 14.063 MHz.
After returning home, I went to the NOAA SWPC Website, and discovered that a Class M4 solar flare had occurred at the time I heard the loud noise on the various HF bands. The flare began in X-rays just before 1830 UT, it was near max at 1845 UT, with the x-ray peak at about 1900 UT. It then continued and slowly dropped until about 2030 UT, when another strong flare began, peaking at about 2055 UT.
The times of the x-ray flare correlate well with the maximum noise I heard near 1846 UT.
I’m curious if others heard this same noise.
If it came from the sun, the noise may have been apparent over most of the sunlit part of the earth, at the same time I noted it - between about 1842 and 1850 UT.
Surely there was a short wave fade (SWF) during the period 1830 to 1930 UT, with a max near 1900 UT. This would have reduced signal strengths on many HF bands with sunlit paths.
I know quite a few others were active at around 1846 UT, but I imagine that the noise and short wave fade may have caused some of you to take a break as I did.
Did you hear the noise? Please reply if you can add to this one report.
There’s still a chance that the strong noise I heard had a more local cause… That there was an interesting double flare is not in doubt!
The flare created a coronal mass ejection, and a geomagnetic storm is predicted (by the experts) for tomorrow, 11 May. That will make for some interesting propagation as well.