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The K7RA Solar Update


The past week was a good one for HF propagation. Average daily sunspot numbers doubled from the previous week, rising from 13.6 to 27, while average daily solar flux rose from 72.6 to 84.3. Average daily geomagnetic numbers were lower, with average planetary A index declining from 21.1 to 9.9 and average daily mid-latitude A index from 17.1 to 7.6.

Last Friday was the autumnal equinox, so we should see a seasonal improvement in HF conditions.

Predicted solar flux is 91 on September 29 to October 1, 89 on October 2-5, 90 on October 6-7, then 85, 76, 75, 74 and 73 on October 8-12, 72 on October 13-15, then 71, 74, 73, 78, 80, 87 and 90 on October 16-22, 95 on October 23 to November 2, then 90, 85, 76, 75, 74 and 73 on November 3-8 and 72 on November 9-11.

Predicted planetary A index is 28, 18, 14, 12 and 8 on September 29 to October 3, 5 on October 4-10, 25 on October 11-13, then 20 and 15 on October 14-15, 8 on October 16-17, 5 on October 18-21, then 16, 8, 20, 25, 20, 10 and 8 on October 22-28, 5 on October 29 through November 6, 25 on November 7-9, then 20, 15 and 8 on November 10-12.

“Geomagnetic activity forecast for the period September 29 to October 25, 2017 from OK1HH.

Geomagnetic field will be:
Quiet on October 6, 23
Mostly quiet on October 5
Quiet to unsettled October 3, 10, 16-21
Quiet to active on September 29-30, October 2, 4, 7-8, 11, 14-15, 22, 24
Active to disturbed on October 1, 9, 12-13, 25

Increases of solar wind, mostly from coronal holes, are expected on September 29 (-30), October (1, 3, 6,) 11-16, (17-18, 21-22, 24,) 25

- New activity on the Sun can dramatically change real development, which has been happening more often lately.
- Parenthesis means lower probability of activity enhancement and/or lower reliability of prediction.

F. K. Janda, OK1HH
Czech Propagation Interested Group
OK1HH compiling weekly forecasts since January 1978”

Dr. Tamitha Skov, the Space Weather Woman, has a new video:

Recent sunspots:

Bob Kupps, HS0ZIA, of Chiang Mai Province in Thailand reported on September 25, “Propagation on 15 meters was much better than the numbers might suggest. I worked 5T5OK, 9J2BO and A25SP on CW all 2-3 hours after sunset on Sep 25. Heard PY1VOY calling the A2 with very strong signals at 1400Z - 3 hours after sunset.” Be sure to check Bob’s page on to see his fabulous location and antennas.

Rich Zwirko, K1HTV in Virginia reported on September 25, about his adventures with weak signals via the FT-8 mode. But first, a review:

From K1HTV, “On Sunday September 24, propagation on the 15 meter band was very good to Europe, the Middle East and Africa and the 21.074 MHz FT8 frequency was packed. The next day, September 25 around 2200 UTC, while listening to 7.074 MHz, the 40 meter FT8 frequency, the band seemed to be in pretty good shape with many European stations being decoded. Running 75 Watts and a wire antenna on 40M, I managed to work VK6RZ and VK7AP both via the long path.

“Switching to 20 meters, as European FT8 stations started to fade out around 0000Z, the start of the September 26 UTC day, the band started to go long. The SFI was 90 and the K index was 0. After working VK6YM via the long path (SE), I moved the beam to the north in hopes that I'd copy some Asian stations over the northern polar route.

“I wasn't disappointed. Over the next three hours, using the new FT8 digital mode and running 75 W to a triband Yagi, I worked 16 stations in Asia. 10 stations were in Japan, 2 in Asiatic Russia, 2 in Kazakhstan and HS5SRH in Thailand. But the best DX of the evening was 9N1AA in Nepal for my FT8 DXCC country #144. The new FT8 mode has caught on worldwide in a big way. It is not unusual, during peak hours, to simultaneously decode between 20 and 30 stations during each 15 second sequence, many of them -20 dB or weaker on the approximately 2 kHz AWGN (Additive White Gaussian Noise) channel.

“The use of FT8 has resulted in the realization that despite what appears to be poor propagation, many DX contacts can still be made on the HF bands.”

On September 28, K1HTV reported: “While I'm at it, I thought that you would be interested to know that in the early hours of September 26 the over the pole conditions to Asia were great.

“Running 75 W and using FT8, I worked HS5SRH in Thailand, 10 JA stations, two UA0s and a pair of Kazakhstan stations. But the best DX worked that evening was 9N1AA in Nepal for my FT8 country #144.

“I was hearing Japanese stations until almost local midnight here at my Virginia location. Forty meter conditions at local dawn were good enough to work a few VK stations. I spent the early to mid-afternoon working FT8 stations in Europe, western Africa and South America, and later working 5W0RA in Samoa and a VK2 station before the band closed.

“By evening and the start of UTC September 27, the polar route to Asia was still good enough to work four stations in Japan, but unlike the previous day, the band shut down hours earlier as conditions started to deteriorate.  During the daylight hours of September 27, 20-meter conditions were pretty good to Europe.

“But by later afternoon, with the K Index climbing up to 7, the northern routes started to suffer. On the positive side, while the K index was 7, I gave 60 meters a try and was happy to work 5T5OK (Mauritania) on CW.

“Using FT8, many European stations were worked as well as XT2AT (Burkina-Faso), which was another new FT8 DXCC entity. This morning (September 28), with the K index still high, I got on 40 meters and was pleasantly surprised when, on FT8, I copied 4S7AB. After only a few calls, the Sri Lankan station was in the K1HTV log for FT8 country #147.”

Rich worked 147 countries with this new weak signal mode in a short period of time, using low power.

For more information concerning radio propagation, see the ARRL Technical Information Service at  For an explanation of numbers used in this bulletin, see

An archive of past propagation bulletins is at More good information and tutorials on propagation are at

Monthly propagation charts between four USA regions and twelve overseas locations are at

Instructions for starting or ending email distribution of ARRL bulletins are at

Sunspot numbers for September 21-27, 2017 were 22, 22, 12, 22, 36, 40, and 35, with a mean of 27. 10.7 cm flux was 73, 77.5, 81.2, 86.9, 89.9, 90.7, and 91, with a mean of 84.3. Estimated planetary A indices were 7, 5, 5, 6, 5, 4, and 37, with a mean of 9.9. Estimated mid-latitude A indices were 7, 5, 4, 5, 5, 3, and 24, with a mean of 7.6.