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ARRL Propagation Bulletin ARLP025 (2017)

ARLP025 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 25  ARLP025
From Tad Cook, K7RA
Seattle, WA  June 23, 2017
To all radio amateurs 

ARLP025 Propagation de K7RA

Average daily sunspot numbers rose this reporting week (June 15-21)
from 4.9 to 29.4. The previous week had four days with no sunspots,
and this week there were no zero sunspot days, hence the dramatic
increase in the average.

Average daily solar flux barely budged from 74.4 to 74.6

Average daily planetary A index went from 7.3 to 9.4, and
mid-latitude A index from 6.9 to 8.1.

Predicted solar flux is 75 on June 23-28, 74 on June 29 through July
4, 75 on July 5-7, 77 on July 8-9, 74 on July 10-14, 75 on July
15-17, then 74, 72 and 74 on July 18-20, 70 on July 21-23, 74 on
July 24-31, 75 on August 1-3 and 77 on August 4-5.

Predicted planetary A index is 12 on Jun 23-24, then 10 and 8 on
June 25-26, 5 on June 27 through July 12, then 20 and 12 on July
13-14, 10 on July 15-16, 5 on July 17-18, 8 on July 19, 12 on July
20-21, then 10 and 8 on July 22-23, then 5 on July 24 through August

Geomagnetic activity forecast for the period June 23-July 18, 2017
from F.K. Janda, OK1HH.

"Geomagnetic field will be:
Quiet on June 27, July 4-5
Mostly quiet on June 28-29, July 1, 3, 7, 17
Quiet to unsettled June 26, July 2, 6, 12, 18
Quiet to active on June 25, 30, July 9-11, 15
Active to disturbed on June (23-24,) July (8,) 13-14, 16

"Amplifications of the solar wind from coronal holes are expected on
June (26-27), July (8,) 9-17, (18).

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

"F. K. Janda, OK1HH"

This weekend is ARRL Field Day. Conditions should be good. Earlier
forecasts had the planetary A index this weekend at 5, but currently
for Saturday and Sunday it is 12 and 10, which is certainly
workable. Predicted solar flux is 75 for both days, better than
recent predictions for June 24-25.

6 meter report from George Hall, N2CG:

"On Father's Day 2017 there was a 6m Es opening from the US East
Coast to the Caribbean and Northern South America region that began
around 2145Z according to spots on the DX spotting Websites and
lasted for about two hours.

"I was returning home (Northern New Jersey FN20wv) after having
Father's Day dinner with my XYL and arrived around 7 PM EDT/2300Z.
Soon after I got on 6m and heard YV50ARV/6 in FJ78 on 50.125 MHz SSB
coming in 59+ and soon had him in my log. Over the next 45 minutes I
worked the following exchanging 59/599 signal reports both ways:

"YV5IUA in FK60 on SSB, PV8ADI in FJ92 on CW, KP4JRS in FK68 on CW,
WP2B in FK77 on CW, and KP4EIT in FK68 on SSB.

"Looking at the DX spots being posted during this opening I counted
about 80 percent JT digital mode spots versus 20 percent SSB/CW mode
spots. Last year during a typical 6m Es opening this was the exact
opposite with about 80 percent SSB/CW spots versus 20 percent JT
digital mode spots being reported.

"So it looks like the JT digital modes have made a very strong and
dominant role on working 6m DX and in such a short period of time.
If the JT digital modes can evolve with faster turnaround times
(like what was recently reported on the WSJT-X reflector); then we
may see 6m DX activity become almost exclusively fast turnaround JT
digital modes and 'the way to go mode to work 6m DX.'"

Interesting article about sunspots, and how they are observed:

Dr. Tamitha Skov mentions Field Day:

Another solar article:

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

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

Sunspot numbers for June 15 through 21, 2017 were 28, 28, 28, 27,
26, 34, and 35, with a mean of 29.4. 10.7 cm flux was 77.4, 73.5,
74.8, 74.9, 73.6, 74.4, and 73.7, with a mean of 74.6. Estimated
planetary A indices were 4, 25, 15, 10, 5, 3, and 4, with a mean of
9.4. Estimated mid-latitude A indices were 5, 18, 12, 9, 7, 3, and
3, with a mean of 8.1.


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