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Propagation Forecast Bulletin #9 de K7RA:

from W1AW Bulletin via the ARRL on March 5, 2010
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Propagation Forecast Bulletin #9 de K7RA:

Propagation Forecast Bulletin 9 ARLP009
>From Tad Cook, K7RA
Seattle, WA March 5, 2010
To all radio amateurs

ARLP009 Propagation de K7RA

Two new sunspot groups appeared on March 1, numbered 1052 and 1053. The total number of sunspot groups appearing over the last month is eleven.

Looking at our 3-month moving average of daily sunspot numbers, the latest for December-January-February is 22.4, for the period centered on January. The average daily sunspot number for the month of February was 31. The fact that this is higher than the latest 3-month average is a welcome trend.

The current 3-month average centered on January 2010 is very close to the 3-month average centered on January 2007, which was 22.7. That moving average has not been as high since. In fact, the closest it has been was February 2007, at 18.5. It was all downhill from there, and that average was below 10 from September 2007 through October 2009. It now looks like we saw three minimums, which is why it was so easy to err when trying to locate the bottom. Several times we hit some low number, decided that things were improving, and then a few months later hit it again.

The three minimums were 2.97 in October 2007, 1.1 in August 2008, and 1.5 in March 2009.

The three month moving average centered on January 2008 through January 2010 was 8.5, 8.4, 8.4, 8.9, 4.9, 3.7, 2, 1.1, 2.5, 4.5, 4.4, 3.6, 2.2, 2, 1.5, 2, 4.2, 5.2, 4, 4, 4.6, 7.1, 10.2, 15.2 and 22.4.

The ARRL International SSB DX Contest is this weekend, and it isn't really certain whether there will be sunspots visible through the whole of the contest. Sunspot groups 1051, 1052 and 1053 will soon rotate over the Sun's western limb. Looking at images from the STEREO spacecraft (, there is a magnetically complex area visible in the upper left quadrant facing Earth, but no sunspot has emerged there. Looking beyond the horizon the only really active area (bright white contrasted against green) appears to be emerging from the far side blind spot in the southern hemisphere. That could be five days away from emergence over the eastern horizon.

The blind spot of the STEREO mission incrementally recedes. On March 1, 88.1% of the Sun was visible to the craft, on April 1, 88.5% should be visible, and 90% visibility will occur some time in June. For the first of December 2010, January 2011 and February 2011 visibility should be 97.4, 98.7 and 99.8%. After that, the two spacecraft continue their journey, but the blind spot shifts to the Earth-side of the Sun, which of course we can see directly.

Earlier this week the prediction for the weekend showed higher activity. Go to and click on March 1. Note the solar flux values for today, tomorrow and Sunday (March 5-7) show predicted solar flux at 84, 86 and 90, with flux staying at 90 through March 13.

Now click on March 4, which was the latest report available by the time this bulletin was written early Friday morning, and for the same period it has shifted way down to 82 straight through March 12. You can go back to that site to get the updated forecast after 2000z (but often after 2100z) today, and on subsequent days.

The same forecast shows quiet geomagnetic conditions with planetary A index of 5 until March 15 and 16, when it rises slightly to 8 and 7. Geophysical Institute Prague predicts quiet conditions for March 5 through 11.

K9LA pointed out a problem with the description of effective sunspot numbers from in last week's Propagation Forecast Bulletin ARLP008.

At we see a plot of SSNe, or effective sunspot number, which is derived from multiple ionospheric sounders. The ionosonde data used is foF2, which is the critical frequency of the F2 layer. It is the maximum frequency that can be reflected back from the F2 layer by a vertically incident beam. The smoother heavy line in the upper SSNe graph uses 24 hours of foF2 data, and the lighter and less smooth line uses 6 hours of data. Using a longer period of data makes the 24 hour line smoother, because it behaves more like a moving average, responding less to short duration changes.

This page, gives a more formal definition of the derivation of effective sunspot number. shows a comparison of SSNe, actual observed sunspot number, and SSNf, a sunspot number derived from the 10.7 cm solar flux. The formula toward the bottom shows * as multiplication, and SSNf**2 I believe means SSNf raised to the second power, a way of showing exponents using conventional characters.

The formula shows a relationship between solar flux and SSNf, but is not set up to solve for SSNf using solar flux. So to test it I entered some sunspot numbers into a spreadsheet, and then calculated 10.7 cm flux using the formula. The relationship came out roughly in line with the same values entered into W6ELprop, which always shows flux values when entering sunspot numbers, and sunspot numbers when flux values are used.

W6ELprop introduces a variation based on date, because of our elliptical orbit around the Sun. At you can see a column for observed solar flux, and another for adjusted solar flux. The adjusted value factors for variations due to Earth's orbit. Note certain dates when the adjusted and observed values are equal. Using those dates with W6ELprop and entering sunspot numbers results in flux values equal to data produced by the formula referenced above.

Many reports on good 10, 12 and 15 meter conditions came in recently, and K9IL wrote last week: "From NW Tennessee in the last 10 days I've picked up 40 new countries from all continents. Using 400w and a homemade 2 el Yagi at 30'. I worked my 1st JA ever on 12m. Worked 5R, VQ9 almost the maximum distance away. No VU yet but 12m has been great." Thanks, Bob.

Richard Vincent, KR7R, lived in Seattle, but retired some time back to Chiang Rai, way up in Northern Thailand. He sits 30 miles from the Burmese border to the northwest, and about the same distance northeast to the Laotian border. From there he operates HS0ZFQ.

Richard writes, "I was complaining about PSK being so hard on twenty meters, then on February 25, I decided to look at 15 meters. Without any sweat whatsoever I proceeded to work 5R8FL (Madagascar), EK1KE (Armenia), OH4TI, DL6TG, and HA1AD (Hungary) to the PSK log. When OH4TI came back he just said WOW? He was as surprised as I was."

"Early the next morning I hooked up with Bob, K6MBY, in Sequim, Washington, and we talked for about twenty minutes with good copy. I run 30 watts to the quad and he was running about the same. After that it was anticlimactic, YL3GP (Latvia), ZS2I (South Africa) and IZ3AX in Padova Italy. So in two days I added another nine countries, all on 15 meters. So tell the boys that from about 0500Z to about 0800Z, noon to 3PM our time, that 15 is good. It fades for the west coast, at least it did yesterday, at 0100Z."

It looks like the best time for Richard, who is around 19.91 N latitude, 99.83 E longitude, to work Sequim, Washington on 15 meters would be around 0000-0130z next week. But 17 meters should give a better shot. For Richard, working Southern California on 15 would be best around 0000-0230z, and 0630-1400z to Europe.

An email arrived from Peter Burokas, KL1HB who has a PO Box in Fairbanks, Alaska, but lives about 65 miles north in grid square BP55. With no internet access, he sends email via Winlink. He lives way off the grid with no commercial electricity, running water, or TV. His email said he worked his first 10 meter contact recently, but nothing about where the other station was located. But don't miss his page at It must be a challenge to harness solar power at 135 miles south of the Arctic Circle. I see that on December 22, according to his grid square, his sunrise was at 2023z and sunset at 2326z. I wonder how many degrees above the horizon the Sun rose? On June 22 the Sun sets at 0827z and rises 3 hours later at 1129z. He must charge his batteries with his solar cells in the Summer.

Ian Drury, W0IMD/G0FXQ in Elbert, Colorado wrote, "I was switching between 12/10m on 18 February. I called an EA8 and a CT1 on 10m, S9 both ways. On 12m, worked GM and ZB2, both S9 again. This occurred between 1716-1728z."

"Openings to South America are pretty commonplace on both those bands from here in CO, but that was the first time I worked EU on both bands with signals truly that strong. I am still amazed and excited by that." In a later email Ian indicated he was using CW.

And finally, it is fun getting messages from new hams who haven't experienced sunspots before. Of course, the sunspot activity we're now seeing isn't much, but it seems great compared to the drought over the past few years.

Here are thoughts from Randy Cook, K6CRC of Los Altos, California.

"I am a relatively new ham, passed the Tech in 2006, the General in 2007, and the Extra Class this January. Due to all the usual reasons, I have not been on the air as much as I'd like. I also have been in the hobby during one of the worst sunspot droughts in a long time."

"I have to admit I have been very skeptical of the claims by old timers of 'working the world with 5 watts' during high sunspot activity. Euro QSOs are not a regular occurrence for me - with the exception of contests, I do not have many QSOs outside North America. The few I do hear are usually the big guns with pictures of their incredible antenna arrays on"

"However, today was amazing. I am thinking maybe the OTs haven't been breathing too much solder smoke."

"I was short on time this morning, so I decided to just spin the dial and listen for a few moment starting at about 1500z. Even with my modest roof mounted vertical, it was solid Europeans on 15 meters in Northern California. I was rewarded with a number of interesting QSOs, including a German ham adjusting a portable 20m antenna and looking for local signal reports."

"The 'wow' moment came when I heard a weaker, but copyable French contest station, F6KHM, CQ'ing for North America with a 'QRP' suffix and '6 watts.' As an experiment, I cranked my Elecraft K3 output to under 10 watts, and returned the call. We had a good conversation and the band held up for about 10 minutes. Solid copy and 55 signal reports. Fortunately his English was significantly better than my French."

"All and all, an interest morning. I have not had this type of experience before. I hope this continues."

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 a detailed 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 February 25 through March 3 were 30, 26, 26, 13, 36, 39, and 39 with a mean of 29.9. 10.7 cm flux was 82.7, 80.5, 78.6, 78.1, 77.9, 79.4, and 80.4 with a mean of 79.7. Estimated planetary A indices were 2, 2, 2, 2, 5, 4 and 6 with a mean of 3.3. Estimated mid-latitude A indices were 2, 1, 0, 2, 4, 3 and 5 with a mean of 2.4.

Source: W1AW Bulletin via the ARRL.

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