Sunspot numbers for August 20-26 were 0, 0, 0, 0, 0, 0 and 0 with a mean of 0. The 10.7 cm flux was 67.6, 66.4, 66.6, 67.3, 67.6, 67.1 and 67.3 with a mean of 67.1. The estimated planetary A indices were 11, 8, 5, 5, 3, 3 and 4 with a mean of 5.6. The estimated mid-latitude A indices were 8, 6, 3, 3, 1, 2 and 4 with a mean of 3.9. Geophysical Institute Prague predicts quiet to unsettled conditions August 28, quiet August 29-30, quiet to unsettled August 31, September 1 quiet, quiet to unsettled September 2 and active conditions on September 3. NOAA and the US Air Force predict the planetary A index for August 28-September 6 at 5, 7, 10, 7, 5, 12, 7, 5, 8 and 6.

Last week's bulletin reported that the sporadic-E season was probably over, but then we heard from Mark Bell, K3MSB, of Airville, Pennsylvania (FM19ut). He reports that nine days ago on August 19, he worked Dave Mueller, KG4NL, in Guantanamo Bay (FK29) on 6 meter CW at 2208 UTC. Dave was weak in Pennsylvania with significant QSB, where Mark was running 100 W into a 5-element Yagi at 20 feet.

Bill Rinker, NE9Z, in Moran, Wyoming, wrote in to ask how the Solar Flux Index is measured. Bill is in the Teton National Forest, about 20 miles south of Yellowstone National Park. The solar flux readings are done at an observatory in Penticton, British Columbia, three times per day; the one we use for the official solar flux is the noon reading. The other readings are done in the morning and afternoon.

You can see all of those readings for the past few years here. The ones to pay attention to are the readings at 2000 UTC (which are shown in the table as 200000 in the second column) and the observed flux values are in the fifth column. The sixth column shows adjusted flux values that are corrected for variations in the distance from Earth to Sun. The adjusted values may be useful for measuring what the Sun is doing, but the observed flux gives an indicator of the relative amount of 2.8 GHz energy that is reaching Earth. 10.7 cm is the approximate wavelength at 2.8 GHz. This page has more detailed information about the solar flux under "Information about the Programme."

Mark Lunday, WD4ELG, of Hillsborough, North Carolina, notes that as the summer season slowly wanes, static on the lower frequencies is subsiding. Mark recently worked VQ9LA on 80 meters CW with 100 W and a modest vertical.

Jeff Lackey, K8CQ, of St Simons Island, Georgia, has written to us before with his observations on the number of zero sunspot days between solar cycles. This time, he sent a graphic showing how this minimum is similar to the one prior to Solar Cycle 19 (the big one) and earlier cycles, rather than more recent cycles after 19. Currently, we have had 48 continuous days of zero sunspots. Jeff said if this continues for the next couple of days, it will be the only cycle minimum since 1855 with two greater than 50 day runs of zero spots. Back then, it was the transition to Solar Cycle 10. It is happening right now, and it happened in 2008, also.

He notes: "There is still DX to be worked -- you just have to be very patient. I heard the V73NF station on 40 meter CW earlier this week (Aug 24) about 1100 UTC, but they didn't seem to be coming back to anyone in North America. So I'm not sure they were hearing very well. They finally went QRT and left a lot of us exasperated. This morning, the KH2/K7BV operation was quite strong, but the QRM for me was too much to be heard. They worked several North American stations from 1230-1300 UTC, but I never could crack the pile up. I've got both DXCC entities before in previous operations, so I wasn't totally bummed out." Jeff works all his DX with a flagpole antenna and by loading up his rain gutter.

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 in The ARRL Letter. 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.