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Propagation Forecast Bulletin #15 de K7RA:

from W1AW Bulletin via the ARRL on April 12, 2013
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Propagation Forecast Bulletin #15 de K7RA:

Propagation Forecast Bulletin 15 ARLP015
From Tad Cook, K7RA
Seattle, WA April 12, 2013
To all radio amateurs

ARLP015 Propagation de K7RA

With sunspot numbers and solar flux up, geomagnetic indices down, and it being Spring time, what could be better for HF propagation? That was the case this week, until Thursday when a magnitude 6.8 X-ray flare and CME erupted, and it seems to be aimed toward Earth. Expect it to arrive on Saturday, April 13.

Average daily sunspot numbers rose this week by nearly 57 points from last week, to 138.1. Average daily solar flux was up more than 25 points to 138.8. The average daily planetary A index dropped by more than half from 9.4 to 4.1.

With solar indices rising, the daily sunspot number reached 162 on April 8 and 163 on April 10, the highest level since January 11 when it was 166.

The latest solar flux prediction from USAF and NOAA sees flux values of 138, 135, and 130 on April 12-14, 125 on April 15-16, 120 on April 17, 115 on April 18-19, 95 on April 20-23, then 100, 105, 110, 115 and 120 on April 24-28, 120 on April 29 through May 1, then rising to a peak of 138 on May 5.

The predicted planetary A index is 5 on April 12, 26 on April 13, 45 on April 14, 8 on April 15, 5 on April 16-22, then 12, 8, 18 and 15 on April 23-26, 5 on April 27 to May 4, and 8 on May 5.

A predicted A index of 45 is a big number. At 2358 UTC on April 11 I received a geomagnetic disturbance warning from the Australian government's Ionospheric Prediction Service: "A full halo earthward directed CME was observed on 11 April with estimated arrival late on 13 April. Geomagnetic activity is expected to rise up to Major storm levels due to the effect of this CME late on 13 April and through most parts of the day 14 April." They predict quiet to major storm on April 13, then major storm down to unsettled conditions on April 14.

The Czech Propagation Interest Group sent a geomagnetic forecast from Petr Kolman, OK1MGW. This appears to be a little early to include the effects of the flare. He predicts active to disturbed conditions April 12, quiet to active April 13, mostly quiet April 14-15, quiet to active April 16-17, quiet to unsettled April 18, quiet to active April 19, quiet to unsettled April 20-22, quiet to active April 23-24, active to disturbed April 25-26, quiet to unsettled April 27-28, and mostly quiet April 29-30.

Jon Jones, N0JK followed up on his comments in last week's Propagation Forecast Bulletin ARLP014 about propagation in the Pacific. He writes, "The distance between Hawaii and Wake Island is around 3,925 km. Or close to the limit of a standard F2 hop, which is about 4,000 km. Thus an optimum F2 path for the lowest possible MUF. Possibly the F2 is off the northern high MUF ridge. Hawaii and Wake Island are both about 20 degrees geomagnetic north. The 6-meter path between Hawaii and Wake Island appears to be reliable and consistent. KH7Y heard the KH9/WA2YUN/b this morning (April 5) from 0500 to after 0720 UTC. The beacon runs 50 watts to a loop antenna."

Bruce Smith, AC4G of Taft, Tennessee (grid EM65pb), several miles north of the Alabama state line, reports: "I was so excited to QSO VK9CZ on 80m CW that I had to write in. Our QSO took place on 3 April around 2345Z when VK9CZ and my location in southern Tennessee were in sunlight at the edge of the terminator. This had to be one of my best QSOs ever due to the level of difficulty, the distance, and no darkness at either location (so my terminator map showed). The VK9CZ signal was S5-S7 on my transmit antenna (vertical). The signal was so strong that my separate receive antenna was not required. Since that date, I have not been able to copy their 80m signal. I guess it was one on my luckiest days to be able to make this QSO."

Sounds like fun! At that day and time, I would expect good propagation on 15 and 17 meters! VK9CZ is the Cocos-Keeling DXpedition, and the path was exactly 10,843 miles, or 17,450 km. Time given of 2345 UTC was 4 minutes after sunrise at the South Pacific end, and 21 minutes prior to sunset on the Tennessee end.

W3HKK sent this account of his participation in a club effort for the CQ World Wide WPX SSB Contest of two weeks ago: "WW8OH and the Cooken ARC Contest Animals had been planning for months to give the WPX contest a shot. The week didn't look promising. SSNs dropping. An indices in the 20s. And warm WX with its high QRN on Fri night in particular were stacked against us.

"DX wasn't that good. 10 was spotty. 15 better but not great. 20-40 were loaded with sigs but nowhere to go.

"WW8OH (400w to a 35 ft high hex beam and a 70 ft high, 600 ft horizontal loop) has been on a quest to score 1000 Qs and 1M points in some contest! ANY contest! So far this year we'd get 600 Qs on Day One, but struggle on Day Two, always falling short, with QSO totals usually in the mid 800s. We were thinking the WPX could do it for us, thanks to domestic and DX contacts being allowed.

"Friday was a steady slog, all night. Heavy QRN hurt scores on 40-80-160m. Saturday was more of the same, but QRN was easing. Around 9 pm Sat night we moved to 40m and began to work them, 1 at a time, then 2, then 3, then a small pile, then stations 10 deep! We were logging them as fast as we could. AC8GX was at the mic. AC8GI was at the laptop. And I was listening for calls and shouting them out. Poor AC8GI. He was getting one call in his left ear, and another call in his right ear, and had to choose which one to go with. Our rates were building (N3FJP software) into the 40s, 50s, 60s, 80s, 100, 120, 140, and peaking out at 149 Qs per hour per the 20 min adjusted number. We were having a BALL! This went on for FIVE hours, till around 2 am Sunday morning. Loud ones, Weak ones. In between ones. Mostly Stateside sigs. Bless the West coast. They were ALL on the air in droves.

"By the time we broke for sleep Sunday at around 3 am, we had already set club records with 1100 Qs and 1M points. What an amazing run on 40m. Nearly half of our total Qs had come on 40m!

"Sunday at 11am we resumed, focusing on 10-15-20m, but without any runs. By 6 pm we were up to 1300 Qs but our (new) dream of hitting 1500 was dying. At 7pm we decided to see if 40M had another run left in it. 7.240 was quiet, and it began again. A few, then more, then another pile up! We spent the last 55 minutes in ham heaven, with rates over 100/hour, until at 7:55 we heard a carrier, followed by music. A broadcast station ended it for us, and we finished with 1449 Qs and over 1.5M points. COOKEN Club records, from our QTH in Fairfield County, Ohio.

"80M gave us a nice couple of hours on Sat night, as well, despite high QRN. But in order of QSOs, it was 40 by a mile, then 20, 15, 10, 80 and finally 160m.

"It feels GOOD to hear the pile up calling YOU! Guys telling us we owned the frequency, were 40 over. DX worked included a smattering of good ones: Antarctica, VK, ZL, JA, DU, YB, CN2R, a fair number from the NE coast of Brazil, some really OLD guys in G, EI, GM, F, and SM5. Guys I remember working back in the 60s! Still going at it, getting a thrill out of contesting. There is hope for all of us!

"So even when propagation is far from optimum on 10-15-20, don't sell 40 or 80m short. On this weekend, 40 meters was in amazing shape for domestic contacts, and gave us a thrill."

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 the numbers used in this bulletin, see An archive of past propagation bulletins is at

Monthly propagation charts between four USA regions and twelve overseas locations are at

Sunspot numbers for April 4 through 10 were 119, 146, 117, 144, 162, 116, and 163, with a mean of 138.1. 10.7 cm flux was 128.5, 134.4, 137, 137.8, 139.2, 146.5, and 148, with a mean of 138.8. Estimated planetary A indices were 4, 3, 5, 5, 3, 4, and 5, with a mean of 4.1. Estimated mid-latitude A indices were 3, 3, 4, 5, 4, 4, and 5, with a mean of 4.

Source: W1AW Bulletin via the ARRL.

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