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Propagation Forecast Bulletin #36 de K7RA:

from W1AW Bulletin via the ARRL on September 9, 2017
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Propagation Forecast Bulletin #36 de K7RA:

Propagation Forecast Bulletin 36 ARLP036
>From Tad Cook, K7RA
Seattle, WA September 9, 2017
To all radio amateurs

ARLP036 Propagation de K7RA

Wow! What a week for solar activity. Although the solar cycle trend is down over the past few years and moving toward a solar minimum around the year 2020, we will still see notable upticks in activity, such as this week's surprising events.

On August 31, reported a G-1 Class geomagnetic storm. Planetary A index was 59. The following day reported geomagnetic unrest with a planetary A index of 19. Planetary A index was 26 on September 2 when reported sunspot group AR2674 "rapidly growing, increasing in both area and sunspot count."

"As the sunspot grows, its magnetic field is becoming unstable, posing a threat for M-class solar flares." Planetary A index was 9 on September 3, when reported two huge sunspot groups facing Earth.

"Behemoth AR2674 has been growing for days, while newcomer AR2673 has suddenly quadrupled in size, with multiple dark cores breaching the surface of the Sun in just the past 24 hours. This movie from NASA's Solar Dynamics Observatory shows sunspot genesis in action:

On September 4, the planetary A index was 18, and reported: "Huge sunspot AR2673, which materialized with shocking speed over the weekend, is seething with activity.

A few days ago in Romania, solar photographer Maximilian Teodorescu captured this snapshot of plasma currents surging inside the sunspot's magnetic canopy, apparently on the verge of an explosion":

Note the recent emergence of large sunspot areas:

We also saw the largest solar flare in over a decade launch Thursday night.

Predicted solar flux is 115 on September 9, 105 on September 10, 90 on September 11-15, 85 on September 16-17, 88 on September 18, 92 on September 19-21, then 95, 98, 100 and 105 on September 22-25, 110 on September 26 through October 2, 105 on October 3-5, then 100, 95, 90, 85 and 80 on October 6-10, 85 on October 11-14, 88 on October 15, 92 on October 16-18, and 95, 98, 100, 105 and 110 on October 19-23.

Predicted planetary A index is 30 and 10 on September 9-10, 8 on September 11-12, then 28, 30, 20, 25 and 12 on September 13-17, 5 on September 18-19, 8 on September 20, 5 on September 21-22, then 8, 5, 8 and 5 on September 23-26, 20 on September 27-29, then 12, 10, 8 and 5 on September 30 through October 3, 15 on October 4-5, 8 on October 6, 5 on October 7-9, 25 on October 10-12 then 20 and 10 on October 13-14, 5 on October 15-16, then 8, 5, 5, 8, 5, 8 and 5 on October 17-23.

Here is the latest geomagnetic activity forecast for the period September 8 to October 4, 2017 from OK1HH:

"Geomagnetic field will be:
Quiet on September 20, 24
Mostly quiet on September 11, 21
Quiet to unsettled September 12, 19, 22, 25, October 2-4
Quiet to active on September 10, 15, 17-18, 23, 26-27, 30, October 1
Active to disturbed on September 8-9, 13-14, 16, 28-29

"Amplifications of the solar wind from coronal holes are expected on September 8-10, 13-19, 27-28, October (1,) 2-4

"Remark: - Parenthesis means lower probability of activity enhancement and/or lower reliability of prediction.

"F.K. Janda, OK1HH Czech Propagation Interested Group"

Lou, VK5EEE sent this, which I edited:

"Do not believe modern-day short-cut internet-gimmicks such as this (he included a reference to an online tool predicting propagation titled "HF Conditions").

"Have a listen to the propagation beacons, tune around the bands!

Remember there is NO SUCH THING generally speaking as a GLOBAL HF one-size-fits-all-situation in spite of the modern trend to paint that picture into their systems. Part of the world is in darkness, part in light. There are many grey areas. The K index varies from location to location. East-West and North-South paths are affected differently by events.

"Nor should we rely on advanced real-time programs such as VOAProp by G4ILO. While useful, these also give sometimes wildly false readings. For example, as I write this, bands including 10m are having great propagation to all of America and to Asia, and perhaps to other places too, while showing that even with 4kW and a big high up Yagi at most S1 signals from a few isolated places north of Australia would be possible. NOT. I just need to tune in to 28200 to hear all the beacons coming in so nice and clear and they are running 100W to simple Ground Plane antennas.

"What does the Australian government have to say about conditions right now on the SWS website? 'Disturbed!'

"Again we may be tempted to take that at face value. 20-10m has not been open much from VK in recent times with very low solar flux and no sunspots at times. However right now, 10m is open. 12m is open, 15, 17 and 20m. Little activity but the beacons are clear, and Costa Rica booming in on SSB on 20m even though the local time here is high noon with the Sun high in the sky.

"If we look at the regional T index map,


"we see that in Australia and New Zealand conditions are actually enhanced.

"If we look at the world map,


"we see that conditions in most of the world are ENHANCED, most of the rest is NORMAL and only a few areas in parts of the Central Pacific and near to the North Pole (parts of Canada, part of Greenland) and northern Siberia are depressed. So why is there so much alarm and DEPRESSED shown as a 'one size fits all' on simple condensed gimmicks? Well, it is true for those few parts of the world. And somewhere the K index is indeed 8, somewhere it is worse, somewhere better.

"Bear in mind that while over today and tomorrow there is a possibility or even a probability of short wave fade-outs (not worldwide but generally on the Sun side of the earth) but the Solar Activity being high to very high means that when there is not a fadeout conditions are most likely to be enhanced! We should be SO HAPPY that solar flux is now well above 100, as that means HF openings occur on higher bands more often.

"With the current predicament of those few radio amateurs who are not hampered by various distractions, the LOCAL NOISE levels are prohibitive on lower frequencies. When bands above 20m open up, we should not be scared off by a glance at the RED/POOR prediction and miss out on all the easy DX with simple antennas and low noise to be had while the higher HF bands are wide open. Let us not forget the IBP beacons, and to tune around and call CQ even when predictions would encourage you do to otherwise."

Lou makes some excellent points. The various propagation models used in the tools for predicting HF success are based on mean predicted sunspot numbers for the month, and cannot predict real time HF propagation. Lou included this URL: .

On September 7, Mark Lunday, WD4ELG in North Carolina reported great propagation to South America on 10 meters using the new FT8 mode.

More about FT8, which is from Joe Taylor, K1JT, can be found at:

Jon Jones, N0JK in Kansas wrote on September 4:

"10 Meters was back Sunday afternoon August 27 for intercontinental DX.

"I had been working the Hawaiian QSO Party on 15 and noted spots for Hawaiians on 10. I went to 10... unfortunately did not hear Hawaii but logged WP4JW FK68 on 10 SSB at 2307z followed by LU5XP FF97 Argentina at 2310z. The QSO with WP4JW was probably double hop Es as I saw many Es contacts spotted around this time on 10. The LU contact may have been Es link to TEP. LU5XP was very loud for about 15 minutes then vanished abruptly. HK1MW was spotted via Es to W3, W7 and W0.

"Stations in Hawaii did work North America on 10 meters August 27, I saw Hawaiians spotted by stations in Florida, Texas, California, Washington State, Oregon and New Mexico."

If you would like to make a comment or have a tip for our readers, email the author at

For more information concerning radio propagation, see the ARRL Technical Information Service web page 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

Sunspot numbers for August 31 through September 6, 2017 were 59, 62, 71, 96, 122, 122, and 79, with a mean of 87.3. 10.7 cm flux was 91.9, 93.4, 100, 120.2, 140, 120.5, and 132.9, with a mean of 114.1. Estimated planetary A indices were 31, 19, 26, 9, 18, 12, and 11, with a mean of 18. Estimated mid-latitude A indices were 20, 17, 25, 10, 16, 11, and 18, with a mean of 16.7.

Source: W1AW Bulletin via the ARRL.

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