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The K7RA Solar Update


Eleven days with no sunspots, but something emerged late Thursday, and it may be the return of old sunspot group 1069. Sunspot group 1069 was visible from May 4-8 before disappearing over the horizon. The return of that sunspot gives a daily sunspot number of 12 for May 20. Sunspot numbers for May 13-19 were 0, 0, 0, 0, 0, 0 and 0, with a mean of 0. The 10.7 cm flux was 69.4, 69.7, 70.3, 68.5, 69.2, 68.7 and 68.6, with a mean of 69.2. The estimated planetary A indices were 4, 3, 4, 4, 6, 6 and 8, with a mean of 5. The estimated mid-latitude A indices were 2, 1, 2, 3, 4, 4 and 7, with a mean of 3.3.

The average daily solar flux for this reporting week (Thursday, May 13-Wednesday, May 19) was down 6.6 points to 69.2. The solar flux for Tuesday, May 18-Thursday, May 20 was 68.7, 68.6 and 68.8. The predicted solar flux for May 21-27 is 70, 72, 72, 74, 74, 74, and 76, while May 28-June 4 is 80. Geophysical Institute Prague predicts unsettled conditions for May 21, quiet to unsettled May 22 and quiet May 23-27. The predicted planetary A index from NOAA and USAF is 8 and 6 for May 21-22, 5 for May 23-28, then 25, 20 and 10 for May 29-31.

Clif Inabinet, KF4UOR, of St Matthews, South Carolina, testifies that he can still have fun on HF with no sunspots. On May 20, 2010 at 0304, he worked KH6QR -- a 4647 mile path -- on 20 meter SSB. He was running 160 W into a 130 foot Windom wire antenna at 39 feet; at the other end was 500 W and a 6 element triband Yagi. You can actually see the KH6QR antenna here. If you click on “Aerial,” select “Bird’s Eye” and zoom in. He is on the west side of Himeni Place.

This is not unusual propagation though, and is an expected path for this time, frequency and date. If you download W6ELprop and enter 33.66 north latitude and 80.77 west longitude for Clif’s end of the circuit, and 19.67 north latitude and 155.98 west longitude for the Hawaii end, then use the date of May 20 and enter a solar flux value of 69, you can see that 20 meter signals should begin to get strong around 0100 and increase in signal strength until 0500; the path should remain open at that signal level at least through 0530. You can also see from W6ELprop how we calculated the length of the path. This prediction also shows a good path on 40 meters from 0430-1130, and 30 meters from 0330-1130.

Sometimes we get requests such as, “Why not just publish on the Web a green light telling me when conditions are good, and a red light when conditions are bad?” The problem is, which of the millions of possible paths between all different locations would the light symbolize, and for what frequency and time of day? Using W6ELprop and an average of several day’s solar flux or sunspot numbers from here, you can calculate the likelihood of propagation between your location and anywhere else for 80-10 meters during any time of the day. This is also useful for looking at the effects of seasonal variations on any path.

Jon Jones, N0JK, in Wichita, Kansas reported working OA4TT (Peru) on 6 meters on May 10 using a loop antenna in his attic. He sent a long list of DX stations who worked stations mostly in the South and Midwest from 2320-2348 that day. Check here for a nice description of the station at OA4TT, who is also N6XQ. Other DX stations on N0JK’s list were TI2NA (Costa Rica), 9Y4D, 9Y4VU and 9Z4BM (Trinidad and Tobago), TG9AWS and TG9NX (Guatemala), YN2N, XE1FAS and XE2OR.

Concerning the same opening, Bob Miles, K9IL, of Martin, Tennessee (EM56) reported that on May 10, “we had a good opening to Central and South America. OA4TT was workable for 2.5 hours Monday afternoon. I worked Louis, HP3TA, also. After I worked Jack, OA4TT, my wife (W9DHD) walked into the shack. I asked her if she wanted to work him. She got him in one call. We run 100 W to 5 elements at 55 feet.”

All times listed are UTC, unless otherwise noted.

Amateur solar observer Tad Cook, K7RA, of Seattle, Washington, provides this weekly report on solar conditions and propagation. This report also is available via W1AW every Friday, and an abbreviated version appears each Thursday in The ARRL Letter. You can find a guide to articles and programs concerning propagation here. Check here for a detailed explanation of the numbers used in this bulletin. An archive of past propagation bulletins can be found here. You can find monthly propagation charts between four USA regions and 12 overseas locations here. Readers may contact the author via e-mail at




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