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ARRL Propagation Bulletin ARLP003 (2011)

ARLP003 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 3  ARLP003
From Tad Cook, K7RA
Seattle, WA  January 21, 2011
To all radio amateurs 

ARLP003 Propagation de K7RA

Average daily sunspot numbers dropped from 50 on the reporting week
ending January 5, to 38 on January 6-12, and now 21.3 on January
13-19.  Average weekly solar flux over the same three periods
dropped from 89.5 to 83.8 to 80.4 over this past week.

The latest solar flux prediction shows a value of 82 for January
21-27 and 88 on January 28-30, followed by 87, 85, 85, 84 and 84 on
January 31 through February 4.  Geomagnetic predictions have the
planetary A index at 5 over the next couple of weeks, except for a
value of 7 on January 22 and February 2-4.

Geophysical Institute Prague expects quiet conditions on January 21,
quiet to unsettled January 22, and quiet January 23-27.

Carl Luetzelschwab, K9LA, has a propagation column in WorldRadio
Online for February 2011 titled "Using Antenna Height As An Aid to
Propagation."  Of course, the higher the better, right?  But Carl
calculates the propagation modes over a particular path at a
particular date and time, and shows how the antenna radiation
pattern at different elevations would affect the signal.

Download the latest issue at

Carl used the propagation prediction program VOACAP, and this
program as well as W6ELprop and others use the monthly predicted
smoothed sunspot number.  The latest predicted smoothed numbers for
January, February and March 2011 are 39, 43 and 47.  They show it
increasing four points every month through July, then three points
from July to August, and two points per month after that, through
June of 2012, followed by one point per month increase through
October 2012, then one point every two months until a peak of 90 in
2013 during February through July.

You can download W6ELprop at and see a
tutorial in PDF format by K9LA at
K4LWS has another guide at

Information on VOACAP is at, and there is a
fascinating online version at
in which you can calculate MUF from any point to any other point.

At you set the time, month and
year, and it generates a coverage map with your station at the
center.  Color coding on the map shows the percentage reliability.
For location, they have many prefixes selectable in a drop-down
menu, or 59 locations in the United States, and 16 across Canada.

As an alternative, you can enter a four or six character grid
square.  You can find six character grid squares by call sign online
at after you create a free account and log in.
Then another drop down gives you a wide variety of antenna heights
for vertical, dipole, and 3, 5 and 8 element Yagi antennas as well
as a theoretical isotropic radiator.

Any of nine HF bands, 80 through 10 meters, are selectable in
another drop down.  The sunspot number used is the International
Sunspot Number, which is lower than the NOAA Boulder number reported
in this bulletin. For each month they use the predicted smoothed
sunspot number for that month.

This tool is fun to play with!  One cool trick is to open the page
in two web browsers, set up parameters (for example) to have
everything equal except the year, then use Alt-Tab (if you are using
Windows) to take you back and forth between the two maps, easily
seeing the differences.  Or you could do the same thing with a page
open in each of multiple tabs in a single browser.  I actually found
this easier than doing the Alt-Tab selection.

So for instance, I set up five tabs in my browser, one for each
month, January through May 2011, and used 10 watts on 10 meters into
a dipole at 10 meters high at 2100 UTC.  It is fun to click through
each tab and see how my 10 meter coverage would change over the end
of this winter and through spring.

Strangely, they have separate pages for the 11 meter band for each
type, point-to-point, and area coverage.  I suppose there are still
operators on the Citizens Band who might want this, and for the
extreme (and illegal) CBer, you can actually select up to 1500
watts, and an 8 element Yagi at 198 feet!  Doing this for March,
2013 sets up an impressive coverage map.  I can hear the howl of
heterodynes now.

Scott Bidstrup, TI3/W7RI sent in an article about creation of a
three dimensional model of the ionosphere that helps explain F layer
anomalies in equatorial regions after sunset.  Read it at online at

Patrick Dyer, WA5IYX of San Antonio, Texas (EL09ql) wrote last week:
"Several 6-meter ZL/VK-US events occurred since around Christmas,
mostly involving just K6QXY or N5JEH (NM). (Check the
lookback/search features on,, or using the ZL/VK calls noted).  IA and
IL got into the Jan 10-11 event.

"The best guess, as this is near the Es peak in each hemisphere for
the Winter and Summer seasons, is Es-Es-F2F2-Es-Es (add another -Es
for the W0/W9 path).  F2F2 is the chordal hop over the geomagnetic
equator where the high ionization levels and effective tilts permit
very low angles of incidence (thus giving much higher MUFs than one
would expect from a "flat" layer). As most of the Es hops involved
are over water there is generally no evidence/warning of any
intermediate signals from along that path.

"The Jan 10-11 event, with its concentrated US hotspot footprint in
AZ, shows this very well as W0/W9 had Es linking them to/thru AZ.
Even during the Cycle 21-23 peak years 6m VK/ZL paths that far to
the US N.E. were rare vs. the numerous events to W6, south W7, W5,
and south W4."

Peter Laws, N5UWY of Norman, Oklahoma had a response to W1YO's
comment in last week's bulletin that "I have been through five solar
cycles and this one is not normal."

Peter writes: "With all due respect to W1YO, a sample size of five
is hardly enough to make a judgment about what is normal.  This
cycle may be different from the previous four or five, but we have
little evidence to determine if any of them is normal!"

"In all, we only have good data on the last 24 or so cycles and
less-accurate data for few more cycles before that."

"But our nearest star is about 4.5 BILLION years old.  That's over
400 MILLION solar cycles!"

True enough, but "normal" expresses what you are accustomed to, as
well as what expectations are. I think many of us wish that Cycle 19
was normal, as in, not unusual and that Cycle 24 was normal as well.

Speaking of what is normal and what is not, occasionally you can
read something in the press quoting someone who seems to be getting
it terribly wrong regarding solar activity. There was a "long range
weather forecaster" quoted this week in the Australian press who
says he uses sunspot activity to make his predictions.  He was
quoted as saying, "There is a huge amount of solar activity and
solar flares at the moment." Don't believe it? Read it at

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 January 13 through 19 were 14, 11, 11, 15, 36,
34, and 28, with a mean of 21.3. 10.7 cm flux was 79.5, 79.3, 80.2,
80.3, 81.8, 81 and 80.8 with a mean of 80.4. Estimated planetary A
indices were 6, 7, 5, 3, 4, 3 and 6 with a mean of 4.9. Estimated
mid-latitude A indices were 4, 6, 2, 3, 4, 3 and 5 with a mean of


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