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The K7RA Solar Update


Solar indicators barely moved this week, with average daily sunspot numbers up 5.8 points to 85.4, and average daily solar flux down 2.4 points to 107.3.

Predicted solar flux for the next week is low, with the predicted average for Thursday August 8 through Wednesday August 14 at 104.9, a little lower than the 107.3 average for this past week.

Solar flux is predicted at 105 on August 9-16, 110 on August 17-18, 105 on August 19-24, 110 on August 25-28, 115 on August 29, 105 on August 30 through September 2, 110 on September 3-4, and 115 on September 5-12.

Predicted planetary A index is 10, 22, 25, 12 and 5 on August 9-13, 12 on August 14-15, 5 on August 16-20, then 10, 15 and 10 on August 21-23, 5 on August 24-30, then 12, 17, 8, 5 and 8 on August 31 through September 4, 5 on September 5-9, and 8 on September 10-11.

OK1HH predicts the geomagnetic field will be quiet to unsettled August 9, quiet to active August 10-11, mostly quiet August 12, quiet on August 13, active to disturbed August 14, mostly quiet August 15-17, quiet to unsettled August 18, mostly quiet August 19, quiet August 20, quiet to unsettled August 21, active to disturbed August 22, quiet to unsettled August 23, quiet to active August 24, quiet August 25-30, and active to disturbed August 31.

In recent bulletin ARLP024 we noted that the site for downloading W6ELprop had a bad link, and then referenced an ftp site. Now that ftp site requires a login, so the best place to find W6ELprop is via K9LA. Go to and click on Tutorials and note the W6ELPropInst270 link.

Many emails arrived this week concerning the sun’s 180-degree flip in magnetic polarity, upcoming at the solar cycle peak. Check out, and

Thanks to K9TF, K6HI, K3MJ, WB0OEW and M0VNG among others for the heads-up.

Here is an interesting comment about the 100-year-sunspot-minima theory:

And check this amazing photo of a sunspot:

Roland Anders, K3RA told us recently about some experiences with unexpected propagation on 15 meters. On August 6, he sent this:

“The antenna is a 3 element SteppIR at 50 feet (DB18 with two “trombones” for 40/30. As for Lawyers Hill, it is not all that high above sea level (about 200 feet) but I have a pretty sharp drop off NE to South. The terrain is not all that high here, about 200 feet, and the land rises steadily to the NNW and around to SW. But to the NE to South it drops off very steadily from my antenna for miles,. So it is a relatively good location.”

“Friday August 2 I worked about 25 Oceana and Asian stations with some Europeans intermixed from 1318 UTC to 1703 UTC. Asia/Oceana included YB, JA, DU, HL, VK8, 9M6, and HS. (All on 15 meters).”

“On Saturday August 3 I worked about 25 Pacific/Asia stations (YB, JA. XV, DU, UA9, VK8) from 1210 UTC til 1350 UTC on 15 meters. I moved to 17 meters at 1430 UTC which was wide open to Europe, and also worked a couple JA’s there at 1500 UTC. At about 1600 UTC I heard a weak SM station in QSO with another European station on 12 meters. I called CQ and worked about 40 European stations until I quit at 1815 UTC. I don’t know how much longer 12 meters was open from East Coast USA to Europe. During that time I worked stations from F to 4X, and as far north as SM and south to CU3.”

“On Sunday August 4, I worked a YB on 15 meters at 1220 UTC, then moved to 12 meters and worked a half dozen European stations on 12 meters from 1230 UTC until 1300 UTC. I was unable to stay on much longer, so I don’t know how conditions panned out the rest of the day on 12 meters.”

“On Monday, August 5 conditions to Asia on 15 meters did not repeat. European stations were present, but not strong.”

“I could not listen until noon today (August 6), but nothing coming through from YB and Europe not strong on 15 meters.”

Thanks Rol!

For more information concerning radio propagation, see the ARRL Technical Information Service at For an explanation of the 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 August 1 through 7 were 88, 112, 104, 75, 59, 61, and 99, with a mean of 85.4. 10.7 cm flux was 112.1, 112.9, 107.3, 104.8, 104.3, 103.9, and 105.5, with a mean of 107.3. Estimated planetary A indices were 5, 4, 5, 16, 16, 7, and 4, with a mean of 8.1. Estimated mid-latitude A indices were 4, 3, 6, 11, 11, 6, and 6, with a mean of 6.7.



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