Propagation de K7RA

21 February, 2009
ARLP008

On February 11-13 we saw a sunspot, then it was gone. Typical of sunspots recently, it was only seen briefly, and this one was a relic of Cycle 23 according to its magnetic signature. For at least a couple of years now we've been expecting Cycle 23 to bottom out and new Cycle 24 spots to emerge, but the sunspot minimum drags on.

Most projections are based on past cycle activity, so according to the timing of past solar minimums, we keep thinking surely soon there will be an explosion of new solar activity, but the Sun seems to tease us.

Our recent experiment with a 3-month moving average of sunspot numbers (see Propagation Forecast Bulletin ARLP006 at, http://www.arrl.org/w1aw/prop/
2009-arlp006.html for the latest update) points to August 2008 as the possible solar minimum. If it turns out to be the end of Cycle 23, that would make 23 nearly 12 years long, only a little longer than the less-than-eleven-year average cycle length.

Tomas Hood, NW7US has a nice image showing the transition from Cycle 23 to Cycle 24 sunspots at,
http://hfradio.org/progress/spotcompare.jpg. I believe the vertical axis represents number of actual sunspots per month, rather than sunspot number, which is entirely different.

Tomas Hood's website at http://hfradio.org/ has information on radio propagation, and you can also hear his twangy guitar when you go to that page.

Geomagnetic conditions were quiet this week, although February 14-15 saw moderate activity. The middle-latitude Fredericksburg A index was just 9 and 6 on those days, and the Planetary A index was 14 and 10. The high-latitude College A index measured near Fairbanks, Alaska was 25 and 22, indicating possibly disturbed conditions over polar paths. February 16-19 and possibly into today show very stable and quiet indicators, similar to the January 7-8, 11-12, 21-25, and February 1-3, and 6-13 periods. All those ones and zeroes for K and A index tell the story at,
http://www.swpc.noaa.gov/ftpdir/indices/quar_DGD.txt.

Geomagnetic conditions should continue to be quiet. NOAA and the U.S. Air Force predict a flat solar flux around 70 for the next month. The predicted Planetary A index for February 20-23 is 8, 12, 8 and 5, continuing at 5 until March 3, when it may rise to 10. Geophysical Institute Prague predicts quiet conditions for February 20-26, except for unsettled conditions February 21-22.

There were a couple of bugs with some links in last week's Propagation Forecast bulletin ARLP007.

The bulletin as displayed on the ARRL web site showed one of the links, mms://max-server.net/2008_vr2bg with the beginning unhighlighted, so when users clicked to try to watch the VR2BG video on OTH radar, they were instead taken to a similar address beginning with http, which does not work. Instead you can highlight the whole URL including the mms beginning, hit Ctrl-C to copy, then open another browser and paste the URL into the web address field by clicking in the field and then hitting Ctrl-V, then the Enter key. At least, this is how it works with Windows machines.

Similarly, the http://www.techblog.tomksoft.com/data/
duga-3/antennas.jpg link, although correct, caused the server to display an anti-hotlinking error message as it detected the redirect from the ARRL web site.

This can be solved like the earlier problem with the mms URL. Just highlight the URL, then copy and paste it into another browser. Works every time. Thanks to George Mackus, AB0RX of Maryland Heights, Missouri for alerting us to the problem.

Find more information on the Chain Home Radar system -- Jim Muiter, N6TP, of San Mateo, California, recommended
http://www.radarpages.co.uk/mob/ch/chainhome.htm.

Greg Andracke, W2BEE of Pine Plains, New York is off to Middle Caicos Island (IOTA NA-002) from March 2-12 as VP5/W2BEE. Greg will be operating CW with just a doublet antenna, and if not on vacation, perhaps he is there to film another documentary. He is a cinematographer (see http://www.imdb.com/name/nm0027996/ and
http://www.andracke.com/) and recently I watched his excellent 2007 Academy Award winning documentary via a DVD from my local library.

Not sure which HF bands he will be on, but he said he will be operating casually.

If you would like to make a comment or have a tip for our readers, email the author at, k7ra@arrl.net.

For more information concerning radio propagation, see the ARRL Technical Information Service web page at, http://www.arrl.org/tis/info/propagation.html.

For a detailed explanation of the numbers used in this bulletin see, http://www.arrl.org/tis/info/k9la-prop.html.

An archive of past propagation bulletins is at, http://www.arrl.org/w1aw/prop/.

Monthly propagation charts between four USA regions and twelve overseas locations are at, http://www.arrl.org/qst/propcharts/.

Instructions for starting or ending email distribution of this bulletin are at http://www.arrl.org/w1aw.html#email.

Sunspot numbers for February 12 through 18 were 11, 11, 0, 0, 0, 0, and 0 with a mean of 3.1. 10.7 cm flux was 69.7, 70.1, 70.1, 69.6, 69.5, 70.6, and 69.8 with a mean of 69.9. Estimated planetary A indices were 4, 3, 14, 10, 3, 1 and 2 with a mean of 5.3. Estimated mid-latitude A indices were 1, 2, 9, 6, 2, 1 and 1 with a mean of 3.1.

Source: The American Radio Relay League

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