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ARRL Propagation Bulletin ARLP018 (2017)

ARLP018 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 18  ARLP018
From Tad Cook, K7RA
Seattle, WA  May 5, 2017
To all radio amateurs 

ARLP018 Propagation de K7RA

Each of the weekly solar and geomagnetic indicators that we track
were lower this week. Average daily sunspot number dropped 10.6
points to 25.1, and average daily solar flux was 4.5 points lower
than the previous week at 76.9.

It is comforting to see though that we have not witnessed a day with
0 sunspots since April 17. Average planetary and mid-latitude A
index were both 5.6, down from the previous week which had planetary
A index at 26.4 and mid-latitude at 18.4.

The A index is expected to remain quiet until May 17-20.

As of Thursday night, May 4, the predicted solar flux is 76 on May
5-8, 74 on May 9-12, 75 on May 13-14, 80 on May 15-18, 85 on May
19-21, 80 on May 22-23, 77 on May 24-27, 75 on May 28-30, 73 on May
31 through June 8, 75 on June 9-10, 80 on June 11-14, 85 on June
15-16, and 88 on June 17.

Predicted planetary A index is 5 and 8 on May 5-6, 5 on May 7-9,
then 8, 5, 8, 8, 5, and 8 on May 10-15, then 15, 30 and 25 on May
16-18, then 45, 50, 15, 10 and 8 on May 19-23, then 5 on May 24-27,
then 12 and 8 on May 28-29, 5 on May 30 through June 1, 8 on June
2-4, and 5 on June 5-10, then 8, 15, 30, 25, 45 and 50 on June

Also related to planetary A index is the OK1HH bulletin from the
Czech Propagation Interest Group:

"Geomagnetic field will be:
Quiet on May 10, 14-15,
Mostly quiet on May 9, 13, 16, 25-30
Quiet to unsettled May 5-6, 22-24, 31
Quiet to active on May 7-8, 11-12, 19-21
Active to disturbed on May 17-18

"Amplifications of the solar wind from coronal holes are expected on
May (5-9,) 16-19, (20).

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

Remember, you can get a new and revised 45-day forecast for solar
flux and planetary A index daily, usually after 2100 UTC from NOAA
at, .

Dr. Tamitha Skov released a new space weather video commentary
yesterday: .

Bob Kile, W7RH of Las Vegas, Nevada noticed a nice sporadic-E 6
meter opening on May 3:

"Spring is here and so was the first sporadic-E propagation on 6m
for the season. There were openings on 6m from the SW to mid-west on
May 2nd and 3rd. I happened to be listening on May 3rd when the band
opened up at about 00:00 to the mid-west. Beacons were copied in
Colorado, Oklahoma, Texas and Kansas. I could not hear the guys in
California but a few in southern Arizona could be heard at times.

"Stations worked were in West Texas, Wyoming, Idaho and Colorado. Of
special note two stations in Cheyenne, WY WY7HR and WY7KY were solid
copy for several hours when the band finally closed about 0200 UTC."

Bob at his home QTH is using a 3 element Yagi on 6 meters mounted
low on his patio. But I think more interesting is his HF remote base
station literally in the middle of nowhere in the Northern Arizona
desert, a good distance northeast of Seligman, and approximately 240
miles from Bob's home in Las Vegas.

You can check his listing or for a deeper

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 April 27 through May 3, 2017 were 23, 35, 34,
33, 11, 25, and 15, with a mean of 25.1. 10.7 cm flux was 78.2, 78,
77, 77.4, 75.3, 77.2, and 74.9, with a mean of 76.9. Estimated
planetary A indices were 7, 6, 6, 6, 5, 5, and 4, with a mean of
5.6. Estimated mid-latitude A indices were 10, 6, 6, 6, 5, 4, and 2,
with a mean of 5.6.


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