Register Account

Login Help

ARRL Propagation Bulletin ARLP008 (2007)

ARLP008 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 8  ARLP008
From Tad Cook, K7RA
Seattle, WA  February 16, 2007
To all radio amateurs 

ARLP008 Propagation de K7RA

The sunspot number is still zero, and the sun appears spotless, at
least from this side.  Helioseismic holography detected a large spot
on the sun's far side on February 5, but another look on February 7
showed a moderate sized spot.  Still unknown is whether it will fade
away before reaching our sun's earth-facing side.  A February 14
reading shows one or two sunspot groups currently on the far side.

For the ARRL International DX CW Contest this weekend, expect more
of the same conditions, with a sunspot count of zero or possibly
eleven (due to the way sunspots are counted, there is no actual
sunspot number between one and ten, even though you will see those
numbers in averages).  Don't expect the highest HF bands to be very
productive, although 15 meters may surprise us, especially if you
are further south (Los Angeles and Miami, vs. Seattle and Boston,
for instance) and also if you work stations in the Southern
Hemisphere.  Operators in the southern states, for instance, may
even find some ten-meter propagation to South America.  Any of those
paths will have a higher MUF.

The IMF currently points south with a solar wind stream in progress,
making Earth vulnerable.  But the solar wind is weak enough that we
shouldn't expect any great geomagnetic disturbances.  The current
prediction is for a planetary A index of 8 for today, February 16,
and 5 through the weekend and into next week.  This is a nice low
number, indicating quiet conditions with low absorption.

The solar flux for today, read at noon local time in British
Columbia, is 74.7.  The U.S. Air Force yesterday predicted solar
flux of 75 for today, and 80 through February 20.  Today the
forecast was revised slightly lower.  It predicts 75 for tomorrow
through February 20.  This suggests possibly more days of zero
sunspots.  After 2100 UTC each day, you can get an update on the
predicted numbers at

This week brought several messages about propagation software.  Some
noted that this bulletin frequently mentions W6ELprop.  This is
because it is easy to use and free, as well as being easily
available.  Each mentioned their favorite propagation software, and
asked that we look at what they are using.

Steve Hammer, K6SGH of Santa Barbara, California suggested VOAProp
from Julian Moss, G4ILO.  This is Windows freeware and serves as a
front end or shell for the free VOACAP software.  VOACAP stands for
Voice of America Coverage Analysis Program, and it was developed by
the U.S. government.

To run VOAProp, you download the setup file from Julian's web site
at  As you install VOAProp, it
directs the user to the VOACAP download site.  When executing the
VOACAP setup file, it is best to let it install in its default
installation directory (itshfbc), right at the root of the hard
drive, at the C:\.

The web site has instructions for using VOAProp, and the first thing
you'll want to do is set it up with your own latitude and longitude.
Then you click on the Solar Data button, and let it download the
predicted smoothed sunspot number for the month, in addition to
current data from WWV.  Then you can set up the month and year, and
if you want, you can easily reset it for sunspot numbers higher or
lower than the current one, to try out different scenarios.

The program has a nice map display, and above it are buttons for
each of the 9 HF amateur bands, plus 160.  Yes, it does include 160
meters, as well as 60 meters and the WARC bands at 12, 17 and 30
meters.  Click a band-button, and the program displays a contour map
showing what signals should be like in all directions from your
location.  These are similar to contour maps showing elevation for
terrain, or weather maps that display contoured areas for
temperature or barometric pressure.

Users may also operate a slide-control up or down for relative
antenna gain and power output.  This is a relative control, not
calibrated to anything, but it is fascinating to see new areas
appear on the signal level contour map as the level of the control
is raised.  It is also very interesting to progress the time from
0000 UTC through the day, which it does in one-hour increments.  You
can watch the shifting contours move across the globe.  My only wish
for improvement would be for the Time control to go past 2400 UTC,
so that you can see what comes at 0100, 0200 and beyond, without
decrementing the control the 23 steps back to zero as you move into
evening time in North America.

You can also see a 24-hour graph of probable signal levels between
you and any particular location.  Just click on the map to draw a
line from you to any spot.  You then click on Show Chart to bring up
the graph.

This program is free, and Julian has a Pay Pal button on his site
for donations from users.

K6SGH, who suggested Julian's software, has his own useful resources
on the web.  Go to and look for a link to the
Moxon Antenna Project, where you can find plans for simple but
effective homebrew gain antennas based on designs by the late Les
Moxon, G6XN.

Thomas Otterbein, DG8FBV was the other person who wrote, and he
suggested WinCap Wizard from Jim Tabor, KU5S, another fine program
also based on VOACAP.  We'll try to get to that soon, but in the
mean time check out the KU5S software at

Dave Gregory, KJ6P/TI5RLI wrote: ''You've probably already mentioned
the one I like: HamCap.  I don't recall seeing it mentioned though.
I like it because it interfaces with DXAtlas with a nice display.  I
run my computer with two monitors and have the HamCap and either
DXSummit or Ham Radio Deluxe -- DX Cluster Analysis on one screen
and DXAtlas on the other''.  I don't think we've mentioned HamCap,
but you can find more information at

If you have a collection of QST Magazine over the past year, check
out a great article by John Raydo, K0IZ, which reviews the currently
popular propagation software.  It is titled ''HF Propagation Software
-- A Look at the Field'', and appears on page 41 in the October 2006
issue of QST.  There is feedback on the article in the December 2006
issue on page 56.

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 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 8 through 14 were 22, 11, 11, 0, 0, 0
and 0 with a mean of 6.3. 10.7 cm flux was 78.4, 76.7, 75.9, 74.7,
73.6, 72.7, and 72.7, with a mean of 75. Estimated planetary A
indices were 7, 4, 3, 2, 7, 17 and 18 with a mean of 8.3. Estimated
mid-latitude A indices were 6, 3, 2, 1, 4, 13 and 16, with a mean of


Instragram     Facebook     Twitter     YouTube     LinkedIn