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The K7RA Solar Update


Tad Cook, K7RA, Seattle, reports: The 10.7-centimeter solar flux rose this week, and on Wednesday May 26 it reached 88, the highest it’s been since December 7, 2020, when it was 89.5. The next day at 2300 UTC, the flux value was 94.2.

The official flux value is always the local noon reading at Canada’s Dominion Radio Astrophysical Research Facility in Penticton, British Columbia, 177 miles northeast of Seattle. Readings are available three times a day.

Average daily solar flux rose this week to 77.8 from last week’s average of 74.2, while the average daily sunspot number increased from 20.3 to 24.9. I hope this signals a return to the enhanced activity and HF conditions we saw at the end of 2020, and a resumption of Solar Cycle 25’s upward climb.

Predicted solar flux over the next month is 83, 81, 80, and 76 on May 28-31; 72 on June 1-3; 73 on June 4; 74 on June 5-10; 75 on June 11; 77 on June 12-15; 79 on June 16-23, and 76 on June 24-29.

Predicted planetary A index is 10, 5, 8, 5, and 8 on May 28 – June 1, then 5 on June 2 and beyond, possibly into mid-July.

Here’s the geomagnetic activity forecast for May 28 – June 22 from F.K. Janda, OK1HH. The geomagnetic field will be:

  • quiet on: May (30 – 31), June 9 – 10, 12 – 13
  • quiet to unsettled on: June 1 – 8, 17 – 20
  • quiet to active on: May 28 – 29, June 11, 14 – 16, 21 – 22
  • unsettled to active: nothing predicted
  • active to disturbed: nothing predicted
  • solar wind will intensify on: May 28 – 30, June (7), 9, (14 – 15, 17 – 19, 22)


 – The increased geomagnetic activity on May 26 – 27 was due to solar flares with CME on May 22. Therefore, it could not be predicted on May 20.

 – Parentheses mean lower probability of activity enhancement.

 – Accuracy of the forecast remains lower.

Jon Jones, N0JK, in Kansas reports:

“The summer 2021 sporadic E season is off to a strong start. Here in Kansas I had Europe in on 6 meters May 19. DK1MAX peaked to –3 dB with audible tones at 1540 UTC. Earliest I have had Europe on 6-meter Es.

May 26 Hawaii to the Midwest on 6 meters. KF0M (EM17) in Wichita had KH6CJJ on Maui up to –4 dB around 2000 UTC. The Hawaiians were in for more than an hour. The mode was FT8.”

Bil Paul, KD6JUI, in Dixon, California, writes:

“Quite a surprise for the solar flux to jump up into the 80s and then the 90s today (Thursday).

“I was trying out a modified small HF loop (homebrew) on my kayak in the Mokelumne River in Northern California today and wasn’t getting out very well. Then I thought I’d give 17 SSB a final try before packing up my gear. Transmitter power was 12 W.

“Heard two VKs coming in loud and clear and managed to catch VK2CPC, Les, just as he finished a QSO. He gave me a 3 × 3 report and managed to get my call sign correct. Fortunately my kayak was in such a position that the loop was aimed toward Australia.

“And, my buddy caught two bass. Good day for both of us.”

Michael May, WB8VLC in Oregon reports:

“Another weird week of non-ham activity on 10 meters to report along with lots of 6 meter activity. The most interesting thing heard on 10 meters was non ham intruders, heard this past Sunday. I was tuning around on 10 meters looking for beacons when I came across some North Korean fishing boats operating on 28.175 and 28.275 MHZ FM mode. This was at 2120 UTC on May 22, and the signals were in for the next 2 hours. The attached recording is condensed from over a 2-hour period [email K7RA for a 836 kB MP3 copy].

“A co-worker listened to the recording and said it sounded like a North Korean dialect and after more research we found that they are most likely squid fishing boats around the Asiatic Russian coast north of Japan and east of mainland Asiatic Russia, where these boats are typically found. The signals peaked on my 4-element, 10 meter OWA at 330°.

“I have not heard these signals in more than 9 years, which leads me to think that a 10 meter FM path to Japan is possible. Research on these boats indicates only 25 W of FM carrier with 102-inch whips.

“No real interesting 10-meter ham contacts to list as the North Korean fishing boats were certainly enough for my 10 meter listing.

“Six meters was my best band over the past 2 weeks for real ham to ham QSOs and here are some of the interesting ones. All of the 6 meter SSB contacts were well over S-9 both ways and the QSOs lasted for more than 45 minutes each, real rag chews.

“On 6 meters SSB/FT8/CW I use my K3S to a 6-element HyGain Yagi on the same boom as my four elements for 10 meters and 500 W from a home-made LDMOS amplifier.

“On 6 meter FM I use the HyGain V-6R stacked 5/8th wave, 25-foot-long co-linear vertical and 110 W with a GE Orion FM land mobile transceiver.

“Six meter contacts, all times/dates UTC:”









FT8 BL01xi




















CW DM95cc










FT8 FN03ht










CW EN33xx










FT8 EJ79xv










SSB FM07pt










SSB FM17ur










SSB EM95pu










FM DM35cd Kingman, AZ










FT8 EN82qb


 N1API reported last week:

“I suppose by now you have heard of the 6 meter opening on May 19. I was fortunate to work a total of 59 stations on FT8. The most amazing thing was that band was still open into Europe at 10 PM local, which would be 2 AM or later in Europe depending on how deep the opening was. Stations from the US were also seen. The next morning at daybreak had signals from Spain and Italy on 6 meters. I can’t remember seeing conditions like this before.”

N4SO reports:

“In the weird category, my signal was picked up on PSKreporter in Ukraine. The notation, a one and only, reads:

Rx at Monday, 17 May 2021 18:08 GMT

From N4SO BY UX0ZAB Loc KN66au15

Frequency 28.074.741 MHz (10m) FT8 –13DB

Distance 9552 kilometers, bearing 36°

The map location shows Ukraine. At that time, I was transmitting, both calling CQ, and working mostly US. UX0ZAB is a monitoring station, and we did not make a contact, other than his reception report of my signal.”

Check this website for synoptic map images.

It has been a long time since we presented anything YouTube | article about the important work of astronomer Hisako Koyama.

Thanks to K5FB for these links:

New Method Invented for Predicting Solar Radio Flux Two Years Ahead

Medium-term Predictions of F10.7 and F30 cm Solar Radio Flux with the Adaptive Kalman Filter

A new solar telescope is planned for the Canary Islands.

Here’s a new video from Tamitha Skov, WX6SWW, the Space Weather Woman.

Sunspot numbers for May 20 – 26 were 13, 13, 19, 30, 29, 36, and 34, with a mean of 24.9. The 10.7-centimeter flux was 72.3, 73.7, 75.6, 79, 72.7, 83.5, and 88, with a mean of 77.8. Estimated planetary A indices were 24, 7, 5, 4, 4, 3, and 13, with a mean of 8.6. Middle latitude A index was 17, 8, 5, 4, 2, 3, and 12, with a mean of 7.3.

For more information concerning radio propagation, visit the ARRL Technical Information Service, read “What the Numbers Mean…,” and check out K9LA’s Propagation Page.

A propagation bulletin archive is available. For customizable propagation charts, visit the VOACAP Online for Ham Radio website.

Instructions for starting or ending email distribution of ARRL bulletins are on the ARRL website.

Share your reports and observations. 



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