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The K7RA Solar Update


Over the past week we saw a decline in solar activity, and the 45-day outlook showed progressively weaker numbers as well.

Average daily sunspot numbers for May 15-21 were 129.4, while the previous average was 142.4, a 13 point decline. Average daily solar flux drifted from 157.5 to 128.5. The daily sunspot number on Wednesday dropped down to 100 and on Thursday it was only 70, a level unseen seen since January 28.

Last week the solar flux prediction for Friday through Sunday on Field Day (June 28-29) was 125 on Friday and 135 on Saturday and Sunday. But the daily forecast on May 19 changed, with predicted solar flux at 120 on all three days, where it still remains. Prior to May 19 solar flux was predicted to peak at 165 on June 10-11, but that has now been revised downward to 135 and 130.

The latest prediction has solar flux at 105 on May 23-26, 100 on May 27-29, 110 on May 30, 120 on May 31 through June 3, 125 on June 4-5, 130 on June 6-7, 135 on June 8-10, 130 on June 11-12 and 125 on June 13-15. Flux values then drop down to 105 on June 22-24.

Predicted planetary A index is 8 on May 23, 5 on May 24-25, 8 on May 26, 5 on May 27 through June 3, 12 on June 4, 8 on June 5-8, and 5 on June 9-16.

F.K. Janda, OK1HH, sends us his weekly geomagnetic outlook. He expects quiet to unsettled activity May 23, mostly quiet May 24, quiet May 25, quiet to active May 26, quiet to unsettled May 27, quiet May 28-29, quiet to active May 30-31, mostly quiet June 1, quiet June 2, quiet to active June 3, active to disturbed June 4, quiet to active June 5, active to disturbed June 6, quiet to unsettled June 7, quiet June 8-9, mostly quiet June 10, quiet to unsettled June 11, quiet June 12, mostly quiet June 13, quiet June 14-16, and quiet to active June 17-18.

Lawrence, GJ3RAX, of Jersey (not New Jersey, but the old Jersey, the Isle of Jersey in the United Kingdom) says “Not much to report from here this time. There have been several more Es openings on 6 meters during the last week but mostly to places within Europe that are already on my list for this year although I have added a few new grid squares to my annual table in the VHF group. Most QSOs have been with Italy and Spain.

“Now hoping to be on at the right time to catch openings again on 4 meters and eventually on 2 meters.”

Lawrence mentioned the 4-meter band, which many may be unfamiliar with. Four meters is used in only a few countries, and the common allocation is 70-70.5 MHz. Apparently Great Britain at one time also had a 5 meter amateur band at 56 MHz. Perhaps 70 MHz will be allocated for radio amateurs in the United States some day. For more information see , and

Pete, K2ARM, of Fort Edward, New York (about 50 miles north of Albany) reported on May 20, “We have had a few openings on 6 meters in May but not for long. Even though the big guns have been working into Europe and South America, I haven't heard much on my dipole. But on May 11 I worked PV8ADI, LU4FPZ, LW3EX, and CX7CO on 6 meter CW plus a few states. I only run 40 watts to a dipole and only use CW.

“On May 18 the band opened up around 1300 UTC and stayed open until 0000 UTC. Signals were 30 to 50 over S9 from the Midwest at times and around 2210 UTC I worked WN6K and AI6O in California. Soon after, XE2CQ came pounding in, but I could not get through. It looks like even though 6 meter sporadic E started out late, it may be better than last year.”

On May 22 Pete wrote, “6 meters was open again last night until late in the evening. There were beacons from everywhere but not many stations on. My dipole is only up 20 feet and I am in a valley, great for DX!”

Thanks, Pete.

For anyone considering six meters, remember that a half-wave dipole is only about 9 feet plus 3 inches long for the low end of that band.

Scott Bidstrup, TI3/W7RI, wrote on May 21: “Those were interesting responses you posted last week to my inquiry about the possibility of VHF propagation as a result of lightning sprites. They seem to confirm what I conjectured. I think investigation of this could be a good subject for someone's PhD thesis.

“The declining solar activity has taken its toll down here on 6 meter propagation. There have been almost no openings the last couple of weeks, and what there have been, were short and rather sparse. I logged the YV4AB beacon about a week ago, as did YS1AG yesterday, the east-west path in both cases demonstrating that sporadic E does exist at these latitudes, though it is much rarer and sparser than in the United States or Europe.”

“Meanwhile, the afternoon transequatorial openings from the States into South America have been continuing almost daily, and even though the paths go right over our heads here in Central America, we're still hearing nothing at all here on the ground. TI5XP has built a high gain beam for six, on a 42 foot boom, and even with it, he's been hearing nothing. I am starting to see some evening TEP in Europe on the maps in the last few days; since that is a different mode, perhaps it will yield us some propagation. We can only hope.”

Scott sent along this interesting article, another one mentioning that huge July 2012 solar flare:

This weekend is the CQ World Wide WPX CW Contest. The SSB weekend was in March. See for further information.

Summer solstice is only four weeks away, at 1051 UTC on Saturday, June 21. To illustrate what summer propagation may be like compared to Spring, I ran some arbitrary numbers on W6ELprop for a path from Cleveland, Ohio to Germany with a sunspot number of 130, on the 23rd of March (near the equinox), April, May (today) and June (near the solstice), all on the 23rd of each month.

Examining 15 meters, in March we see the path begin to heat up around 1200 UTC, becoming quite promising at 1400 UTC with a relative signal level of 47, changing to 48 at 1700 UTC, 50 at 1900 UTC, 51 at 2000 UTC, 52 at 2100 UTC and 53 at 2200 UTC. Then prospects begin to fade until the path is unlikely to support propagation by 0100 UTC.

For the same path on April 23 we see 15 meters begin to open at 1230 UTC, with a relative signal level rating of 45 but with chances of an opening increasing at 1830 UTC with a signal rating of 47. The signal increases to 50 at 2030 UTC, but the path begins to fade between 2200-0030 UTC.

For today (although recent sunspot numbers are not as high), we don’t see much chance of propagation until 1430 UTC with signal ratings gradually increasing from 43 to 45 at 1800, 47 at 1930, 50 at 2130, 52 at 2300, then fading after 0000 UTC.

A month from now we see poor prospects around the clock, with a D-rating (less than 25 percent chance) from 0430-0800 UTC, and C-rating (25-50 percent chance of opening) 0830-0400 UTC. So the summertime propagation on 15 meters is much poorer than at the spring equinox.

If we look at much higher numbers, such as a sunspot number of 250 instead of 130, we do see improvement, with several periods of B (50-75 percent) ratings.

K9LA has the W6ELprop software (for Windows) as well as tutorials available at his site, If you want to guess what propagation might be like next month from your Field Day QTH to various targets around the United States, you could download the program and perhaps make an average of predicted solar flux over the weekend and several days prior, and plug that number into the program instead of sunspot number. See a daily update of predicted solar flux and planetary A index for the next 45 days at .

Let’s hope for the best, an extension of this current solar cycle peak, rather than weakening and decline in solar activity.

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 e-mail distribution of ARRL bulletins are at

Sunspot numbers for May 15 through 21 were 130, 136, 146, 138, 130, 126, and 100, with a mean of 129.4. 10.7 cm flux was 152.1, 138.7, 133.5, 127.5, 116.9, 117.2, and 113.9, with a mean of 128.5. Estimated planetary A indices were 5, 5, 4, 5, 4, 4, and 3, with a mean of 4.3. Estimated mid-latitude A indices were 5, 6, 4, 5, 4, 4, and 3, with a mean of 4.4.




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