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ARRL Propagation Bulletin ARLP042 (2010)

ARLP042 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 42  ARLP042
From Tad Cook, K7RA
Seattle, WA  October 22, 2010
To all radio amateurs 

ARLP042 Propagation de K7RA

Average sunspot numbers for the week were up nearly 44 points to
55.6.  Average solar flux readings were unchanged, at 84.9.  For a
few days solar flux values rose above 90, but currently the
projection from USAF and NOAA for solar flux over October 22-31 is
82, 82, 82, 82, 80, 80, 80, 80, 80 and 80.

The same forecast predicts planetary A index for the same period at
5, 10, 15, 12, 5, 5, 5, 5, 7 and 7.  Geophysical Institute Prague
predicts quiet conditions on October 22, quiet to unsettled October
23, unsettled October 24-25, and quiet October 26-28.

Seven new sunspot groups arrived this month, with group 1112
appearing October 9, group 1113 on October 13, 1114 and 1115 on
October 14, 1116 on October 17, 1117 and 1118 on October 19.  While
the average sunspot number for the past week was 55.6, the greatest
sunspot activity was over the past few days, with the daily sunspot
numbers on October 17-20 at 61, 69, 65 and 61. On October 21 the
sunspot number dropped to

Check the new November issue of "WorldRadio Online" for two articles
of interest concerning propagation.  The first is a piece beginning
on page 14 about gray line propagation, and on page 38 is Carl
Luetzelschwab's excellent monthly Propagation column.  This month
Carl addresses questions that arose when news articles appeared
describing a shrinking thermosphere.  Did this affect propagation?
Carl's data shows that it probably did not.  You can find a new
WorldRadio online on the twentieth of each month at

Last week's Propagation Forecast Bulletin mentioned the WSPR program
and the article about it on page 30 in the November 2010 issue of
QST.  A useful tool generated by this network is the map at  You can look at weak-signal
propagation over all bands for the past 24 hours, or look at any of
the dozen individual amateur bands from 2 to 160 meters, plus VLF.
You can limit your view down to 30 minutes, 1 hour, 3 hours, 6
hours, 12 hours or 24 hours.

WSPR is not a mode where you can converse with other stations, but
rather an automated network that picks up weak signals from other
stations in the network and displays the propagation paths.  Because
it is effective with such weak signals, it isn't clear how this
might be used to indicate a possible path for an SSB QSO, for

Jim Muiter, N6TP of San Mateo, California says that on Thursday
morning he picked up the 10 meter NCDXF beacon ZS6DN in South Africa
around 1700z, and it disappeared a few hours later.  In the past,
this has been an indicator of improving conditions.

The Northern California DX Foundation operates beacons worldwide on
10, 12, 15, 17 and 20 meters.  These are very useful for determining
when the bands are open.  Check it out at

In response to W7EET's query in last week's bulletin, Dave Parslow,
VK3AIF of Melton, Victoria, Australia (about 25 miles WNW of
Melbourne) wrote to tell us about a web site that the Australian
government operates that uses real time ionosonde (ionospheric
sounder) data to predict propagation.  Unfortunately, we don't have
a system like that here, but it can be used to predict propagation
from North America back to the South Pacific.

Dave wrote, "I don't know if you have a similar service available in
North America, perhaps I should research that before putting pen to
paper so to speak but what I use here is the Hourly Hap Charts
published by the Australian Government Ionospheric Prediction

"The IPS posts these charts hourly using near real time data
gathered from Ionograms, a list of their locations is also available
on the above site and overlay a map with colored contours
representing different frequencies in the HF spectrum.  They can be
read at a glance and the optimal frequency determined for your
particular path of interest.

"How I use them is to go to
in my java enabled browser and select my approximate location from
the drop down list and the map appears centered on my preferred
position.  There are many other useful tools on the site also with
many having the Amateur bands selectable from the options."

Thanks, Dave!

Stan Gubiotti, VE7IEF of Abbotsford, British Columbia asked what I
think is happening with solar Cycle 24, and when the peak might

I think Cycle 24 is weak!  Regarding the peak, I will refer to the
NOAA space weather Preliminary Report and Forecast, available from

The latest issue with a cycle forecast is PRF-1831 from October 5.
On page 10 we see a table showing the smoothed sunspot number
predicted to peak at just 90 between February and July in 2013.
Unfortunately this table doesn't have the months labeled across the
top, but I can assure you that the left hand column is always
January, and the right hand column is December.

Stan also asked about the meaning of various terms used in this
bulletin, and for this question I refer him to the links toward the
bottom of this bulletin.

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  Find more good
information and tutorials on propagation at

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

Instructions for starting or ending email distribution of ARRL
bulletins are at

Sunspot numbers for October 14 through 20 were 34, 51, 48, 61, 69,
65, and 61, with a mean of 55.6. 10.7 cm flux was 80.4, 82.2, 86.9,
83.6, 90.6, 86.6 and 83.9 with a mean of 84.9. Estimated planetary A
indices were 2, 5, 6, 11, 5, 5 and 4 with a mean of 5.4. Estimated
mid-latitude A indices were 0, 3, 3, 10, 3, 7 and 3 with a mean of


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