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ARRL Propagation Bulletin ARLP010 (2013)

ARLP010 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 10  ARLP010
From Tad Cook, K7RA
Seattle, WA  March 8, 2013
To all radio amateurs 

ARLP010 Propagation de K7RA

The averages of daily sunspot numbers and solar flux over the
reporting week (February 28 through March 6) both rose, with sunspot
numbers up nearly 36 points to 93.3 and solar flux up nearly 12
points to 112.6, in comparison to the previous seven days. The most
active geomagnetic day was Friday, March 1, when the planetary A
index was 27 and the mid-latitude A index was 23. Alaska's high
latitude college A index was a whopping 64. The upset was sparked by
a stream of high speed solar wind.
The latest forecast from NOAA/USAF puts average solar flux for the
next five days (March 9-13) at 118.2, higher than average solar flux
for the reporting week, which was 112.6.
Predicted solar flux is 112 and 118 on March 8-9, 120 on March
10-11, 118 on March 12, 115 on March 13-14, 105 on March 15, 95 on
March 16-17, 100 on March 18-20, 105 on March 21-24, 110 on March 25
through April 1, and 105 on April 2-5.
The predicted planetary A index is 8 on March 8, 5 on March 9, 8 on
March 10-12, 5 on March 13-20, 8 on March 21, 5 on March 22-27, then
18, 10, 5 and 10 on March 28-31 and 8 on April 1-4.
F.K. Janda, OK1HH predicts quiet geomagnetic conditions on March
8-9, mostly quiet March 10-11, quiet to unsettled March 12, quiet to
active March 13, quiet on March 14, quiet to unsettled March 15-17,
quiet on March 18, mostly quiet March 19-20, active to disturbed
March 21-22, quiet March 23-24, mostly quiet March 25, quiet March
26-27, quiet to active March 28-30, and quiet to unsettled March 31.
Have we mentioned recently that for HF propagation, we generally
want higher sunspot numbers but low geomagnetic indices at the same
At you can see the
latest NASA solar cycle prediction. They revised the forecast
downward again. Last month they said that the cycle should peak this
Fall with a smoothed sunspot number of 69. That was revised down by
three points, and now they say it will peak at 66. These are
International Sunspot Numbers, which have a lower scale than the
Boulder numbers we use in this bulletin, which run about 35% higher.
Many readers wrote in concerning the news about a possible
double-peak for the current solar cycle. There seemed to be a peak
in activity around the end of 2011, then activity fell off last
year. If true that the cycle peaks this Spring or Fall, we don't
seem to be trending toward that activity yet.
Check for a video from
NASA explaining this.  Note you can watch the video in HD and full
screen by selecting options at the bottom.
Thanks to John Campbell, K4NFE, Elwood Downey, WB0OEW, Gary Johnson,
K5SWW, and David Dary, W5ZAX, for the tips on the story.
If you go to for the
latest Preliminary Report and Forecast and turn to page 15, you can
check the numbers for the latest prediction from Boulder. It shows a
peak in September and October 2013, with levels about 27% higher
than solar activity last month, February 2013.
See also that the peak in activity at the end of 2011 is represented
by the higher numbers (smoothed, so the peak is not pronounced),
then gradually declining. The averaging function seems to have moved
that peak out to February and March of 2012. But the predicted peak
this year is quite a bit higher than the previous peak. Let's hope
that the second peak is indeed much more robust, as predicted.
At the forecast from
last month shows higher values for the end of 2012 and the first few
months of 2013. These reflect estimated future sunspot numbers,
which would drag the average down. The numbers for each month are an
average for a year's worth of data, six months forward, and six
months back. The estimate for March 2013 went from 77 last month to
73 this month. The latest figure represents one more month of real
recorded data than last month's prediction.
Note also on the next page that the solar flux prediction shows the
peak for that parameter in August 2013.
Julio Medina, NP3CW of San Juan, Puerto Rico wrote, "Just to let you
know that today 01 March 2013 from 1826-1837z I worked VU3WIJ and
VU3WII on 20 meter SSB with 5x9 reports both way. I was using a
vertical antenna at ten feet above the ground and 100 watts.  Both
stations had pile ups and they copied my signal very easily."
I replied, "On that day I would expect the band to just begin to
open at that time, but signals should reach a peak from 2100-2300z."
Steve Hawkins, NG0G wrote: "On March 5 at 2213Z I had just worked
TX5K (Clipperton Island) on 24 MHz CW. I live in Boone Iowa and it
was getting on toward late afternoon." (See for
the Clipperton DXpedition.)
"After working TX5K I stumbled across XT2TT (Burkina Faso) on the
same band. Since by then it had been dark in Africa for hours I was
very skeptical and thinking pirate. But I adopted the standard 'Work
now, worry later' mode.
"I'll admit it took tweaking everything built into my FT-1000 MKV
Field, and listening so hard there may have been arcing inside my
skull, but I could hear them. I called and worked them about the 3rd
call. At first I thought 'nooooooo, this must be a pirate,' as with
my wimpy vertical, and the solar flux as low as it is, 24 MHz should
not be open to Africa from Iowa at 2213Z. I was astounded when not
only did they answer me, but I quickly showed up in their online
"I could almost hear (cue
the Twilight Zone theme music.)
"Despite feeling like the guest on a certain late night talk show, I
quickly launched into my best post-back surgery version of the
'Happy Dance.'
Talking later with a friend, K0KT, he reminded me that near to the
equator, the MUF can be surprisingly high up to midnight."
Actually when running the numbers on W6ELprop, propagation over that
path at that time on that band is not unusual. I entered 42.07
degrees North, 93.88 degrees West for Steve's location, and found
the XT2TT DXpedition QTH at,
That page shows a grid square location of IK92fi, so I entered this
into the AMSAT grid square conversion tool at
This yielded 12.3542 degrees North, 1.54167 degrees West for XT2TT.
This turns out to be only 25 miles north of the default Burkina Faso
coordinates in W6ELprop.
Based on these coordinates, the station is in the southwest portion
of Ouagadougou, Burkina Faso's capitol city. I checked this at 4:17
AM Seattle time today, which is 12:17 PM in Burkina Faso and also
1217z. The temperature was 102 degrees F with humidity of only 11%
in Ouagadougou. The annual rainfall there is only 35 inches, and the
high temperatures between March and May reach 113 degrees F.
The path length is 5,767 miles (9,281 km), and on March 5 W6ELprop
shows an opening beginning with a B rating (available 50-75% of the
time) and signal-to-noise ratio of 40 dB at 1330z, changing to an A
rating (opening 75-100% of the time) by 1430z. By 1830z the s/n
ratio is 43 dB and it gradually increases to a peak of 48 dB at
2300z. Signals stay at that level, but availability degrades to a B
rating at 2330-0000z, C rating (25-50% availability) at 0030z and D
rating (1-25%) at 0100-0130z.
Sunset at XT2TT was 1812z on March 5, and at NG0G it was 0006z. So
that path opens about 45 minutes after sunrise at NG0G (1248z), gets
better after sunset at XT2TT, and finally begins fading around
sunset at NG0G. A half hour after sunset in Iowa, that path is done.
For more info on using W6ELprop, see references at the bottom of
this page, or check
You can download W6ELprop at
Ken Miller, K6CTW of Rancho Cucamonga, California wrote, "I was up
late last night working on the computer and saw that the Clipperton
DXpedition was operating on 80 meter CW near the bottom end of the
band. Just to satisfy my curiosity I turned on the 1960s station
I've restored (Heathkit DX-60 with homebrew DDS-VFO and Drake 2-B
receiver with 2-BQ Q-Multiplier feeding an inverted-vee dipole
antenna) to see what I could hear. (Ken runs the old Novice power
limit on this rig, just as he did on the same setup in 1967, 75
watts, or about 40-45 watts out.) Their signal here in Southern
California was 20 over S-9 or better so I loaded up the DX-60 and
gave a call after figuring out where the operator was listening (he
was running JAs).  Imagine my amazement when he came back to my
call! I am always impressed that the operators at these DXpeditions
can sort out a weak signal like mine out of the unbelievable racket.
Thanks to them and also, what a surprise to see how good
communications can be on the low bands late at night."
Ken wrote in a subsequent email: "I've restored this first DX-60
(and a Drake 2-B and 2-BQ Q-Multiplier) to get my feet wet. I am now
in the process of rebuilding another DX-60 kit with all new parts. I
re-plated the chassis and all the metal, and I've added an OA2
voltage regulator tube to the power segment of the 6CL6 oscillator
section. That will prevent chirp on 10 meters.
"The VFO is a home brew DDS unit using the now 'retired' FCC-1 and
FCC-2 from The NorCal QRP Club. For details, check the April or May
issue of Electric Radio as Ray is publishing an article I wrote
about my experience.
"I'm also home-brewing another improved version VFO using Jim,
WA1FFL's DDS unit.  This one is a significant upgrade to the unit
described in the article."
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 February 28 through March 6 were 63, 88, 90,
115, 103, 106, and 88, with a mean of 93.3. 10.7 cm flux was 105.5,
112.5, 111, 112, 114.3, 118.4, and 114.3, with a mean of 112.6.
Estimated planetary A indices were 7, 27, 12, 7, 4, 4, and 3, with a
mean of 9.1.  Estimated mid-latitude A indices were 8, 23, 14, 6, 4,
3, and 4, with a mean of 8.9.


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