Register Account

Login Help

ARRL Propagation Bulletin ARLP019 (2010)

ARLP019 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 19  ARLP019
From Tad Cook, K7RA
Seattle, WA  May 14, 2010
To all radio amateurs 

ARLP019 Propagation de K7RA

This lack of sunspots is bothersome.  Thursday (May 13) is the fifth
day in a row with no spots, and there is no sign of any change.
Solar flux has been declining, and is now below 70.  Predicted solar
flux for May 14-19 is 70, then 74 on May 20, 75 on May 21-22, 76 May
23, 78 May 24-25, and 80 for May 26-31.  Higher solar flux tends to
correlate with more sunspot activity.

The same forecast (actually from NOAA and USAF) calls for planetary
A index of 7 for May 14, 12 for May 15-16, 8 on May 17, 5 on May
18-19, and 13 on May 20.  Geophysical Institute Prague predicts
quiet to unsettled conditions May 14, unsettled May 15, quiet to
unsettled May 16, quiet May 17-19, and unsettled May 20.

Prior to all this quiet we saw nine new sunspot groups emerge
between April 28 through May 8, and high daily sunspot numbers of 70
and 77 for May 4-5.  You can see the sunspot numbers for the first
three months of 2010 at,
for the indices since April 1.

Luke Steele, VK3HJ, sent a report from Australia on May 13, where
Autumn began as Spring started in the Northern Hemisphere, and
Winter begins in late June.  Luke's grid locator is QF22it, and he
is in Southeast Australia in Victoria.  Luke writes, "Just when we
were enjoying improving propagation, conditions have subsided again.
Until about a month ago, all bands were working reasonably well, but
with the onset of winter, all seems to have gone quiet. Tonight, I
had to abandon an 80m club net, as I couldn't copy stations 50 miles
away. A VK5 station called in, reporting VK3s strong there, about
500 miles away. This happened last winter also. DX worked this
evening, JD1BMK on 20m CW about 569 here, and a special event
station HL30GDM in Korea on 40m, about 579. With a spotless Sun, and
not much happening on air, I will finally get onto some repairs to
the boat anchors, construction of my High Performance Software
Defined Radio kit, work on my 160m vertical antenna, and catch up on
my QSL'ing!"

Luke is experiencing that 80 meter condition in which the maximum
usable frequency beaming straight up is not high enough to support
regional communications.  You can see it in the foF2 readings for
Australian ionosondes at Canberra,
and Brisbane,

The foF2 reading is taken by beaming a radio signal straight up as
it is swept through the HF radio spectrum, and measuring the highest
frequency that reflects back.  Because local and regional 80 meter
coverage depends on this high angle radiation, the foF2 number is a
good indicator of the viability of regional coverage.

At you can find
data for those same locations back through February, and many other
locations as well.

Check out Luke's page at and click on
his photo for a closer look.  Note that recently Luke has worked as
a farrier.  K5DHY has an image of a recent QSL from Luke at,

Bob Elek, W3HKK in Central Ohio had some excitement on 6 meters
recently. On May 8 Bob wrote, "The sudden rise in sunspots and high
K levels of May 3-4 caused a previously dead band to explode with
signals from the Gulf Coast of FL, GA, SC, and even TX, KP4 and C6.
Dozens of signals peaked 59+ on my 40M ground plane antenna. Stunned
by what I was missing, I rushed out and bought a 5 el 6M Yagi,
assembled it onto a 6 ft high mast strapped to my propane grill on
the back deck, and turned by the Armstrong method. Alas, the band
has been quiet ever since, even for tonight's 50 MHz Sprint.  But
I'll be prepared for the next opening! The season is nearing for
sporadic-E, I am told."

Scott Craig, WA4TTK has an updated data file for his solar data
plotting utility.  Download it from, and you can display solar flux
and sunspot numbers back to January 1, 1989.  In subsequent weeks
you can update the data by copying the latest propagation bulletin
from and
pasting it into a plain text file, then reading the file with
Scott's program to automatically insert the data into the database.
If you are using Windows, you would highlight the bulletin text, hit
Ctrl-C to copy, then open Windows Notepad and past using Ctrl-V.

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,

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

Sunspot numbers for May 6 through 12 were 45, 24, 23, 0, 0, 0, and 0
with a mean of 13.1. 10.7 cm flux was 79.1, 79, 78.8, 75.4, 73.6,
73.5 and 71.2 with a mean of 75.8. Estimated planetary A indices
were 10, 9, 6, 4, 5, 8 and 5 with a mean of 6.7. Estimated
mid-latitude A indices were 6, 10, 4, 1, 4, 6 and 4 with a mean of


Instragram     Facebook     Twitter     YouTube     LinkedIn