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ARRL Propagation Bulletin ARLP021 (2012)

ARLP021 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 21  ARLP021
From Tad Cook, K7RA
Seattle, WA  May 25, 2012
To all radio amateurs 

ARLP021 Propagation de K7RA

Average daily sunspot numbers declined seven points over the past
week to 110.3.  Average daily solar flux dropped 3.3 points to 131.
Unsettled geomagnetic conditions over the past few days most likely
resulted from an interplanetary shock wave originating from a solar
flare on May 20.  Predicted planetary A index is 8, 5, and 8 on May
25-27, then 5 on May 28 to June 4, then 8, 12, 15, 10 and 8 on June
5-9, then 5 on June 10-11, 8 on June 12-13, 5 on June 14-16, then 8,
15, 10 and 8 on June 17-20, and 5 on June 21-25.
Predicted solar flux is 115 on May 25, 110 on May 26 through June 1,
125 on June 2-3, 130 on June 4, 135 on June 5-9, 130 on June 10, 125
on June 11-12, and 120 on June 13-15.  Six new sunspot groups arose
since May 15, one each on May 15, 18, 20, 22, 23 and 24.  Until June
4, predicted solar flux values are below the average for the past
week, 127.7.
We are again receiving geomagnetic forecasts from the Czech
Republic, this from Frantisek K. Janda, OK1HH of Ondrejov, from the
Czech Propagation Interest Group.  He predicts quiet to unsettled
conditions on May 25-26, quiet on May 27-28, mostly quiet May 29,
quiet to active May 30, quiet May 31 to June 1, mostly quiet on June
2, quiet to unsettled June 3, quiet to active June 4, active on June
5, quiet to active June 6, active on June 7, quiet to active June 8,
quiet to unsettled June 9, quiet June 10-11, quiet to active June
12, mostly quiet June 13, and quiet to unsettled on June 14-15.
OK1HH says that on May 30-31 and again on June 5 there is a high
probability of changes in the solar wind, which may cause changes in
the magnetosphere and ionosphere.
Bill Lauterbach, WA8MEA of Hanover, Michigan had a question about
MUF (Maximum Usable Frequency) and LUF (Lowest Usable Frequency).
He says the LUF seems to have changed so that it is sometimes close
to the MUF in the current cycle.  He wonders if LUF should be lower
when MUF is higher.
We passed this on to Carl Luetzelschwab, K9LA.  Carl commented, "The
MUF is determined by the amount of ionization - most of the time
it's the amount of ionization in the F2 region that sets the MUF.
And you can't do anything to your station to change the MUF."
"The LUF is essentially determined by absorption in the D region.
You can lower the LUF on a given path by increasing transmit power
or increasing your antenna gain or somehow reducing your man-made
noise.  In essence your LUF is the frequency at which the received
signal is at your noise level."
"Since a higher MUF means more ionization, it seems to me that
generally there would be more absorption, too, which would increase
the LUF."
Thanks, Carl!
Another Carl, N5XE, Carl Hickman of Sulphur, Oklahoma wrote "On
Thursday evening (0330 UTC Friday, May 25, 2012), I called CQ on 15
meters.  TA2KN answered my call with a 599 plus signal.  He was so
strong, I was hearing an echo on his signal (both short and long
paths), which made copy somewhat tough.  Both paths were strong --
he was LOUD!  I had to use my attenuator to lessen the effects of
his long path signals."
"Less than 10 minutes later, I worked N5RB on the same band (short
skip for me).  After 33 plus years as a ham, I am still amazed at
propagation conditions that crop up from time to time.  It's always
fun to participate in rare openings on the bands."
Thanks, Carl.  TA2KN is at a scout camp in Turkey, where they have
quite a nice antenna system.  Carl worked them at what is probably
the best time of the day on 15 meters over that path at this time of
year.  I see that the short skip distance that Carl mentioned
between N5RB (Ecru, Mississippi) and N5XE in Oklahoma is 452 miles.
I calculated that by looking up their licensed addresses on a map,
then using the latitude and longitude for each station to calculate
distance on W6ELprop.  Carl heard the station in Turkey on both long
and short paths, and those distances are 6,194 miles and 18,680
miles.  This was calculated using the location for the scout camp
shown on, which is 41.07 degrees north
latitude, 29.117 degrees east longitude.
Don Kalinowski, NJ2E of Cary, North Carolina alerted us to the
National Air and Space Lecture Series, and one about the Solar
Dynamics Observatory.  See it at and
click on the View Archived Recording link to watch the 71 minute
video, titled "The Solar Dynamics Observatory:  The Sun Up Close and
Jon Jones, N0JK of Lawrence, Kansas fills us in on 6 meter activity
with a station in Argentina.  He wrote, "Some interesting
propagation on 6 Meters the afternoon of May 19."
"K0HA EN10 NE reported working LU1DMA around 2010 UTC.  I went out
portable with a 2- element Yagi."
"Initially I heard no signals other than the WB0RMO/b EN10 on
"Then at 2105 UTC, LU8YD appeared on 50.110 on an otherwise dead
band.  Weak, then built up to a reasonable signal."
"Called him, and he replied.  Gave me a '5x5' and copied EM28 fine.
His grid is FF51 and logged at 2108 UTC.  I see Alex was spotted by
K2ZD and a W3."
"This was probably an 'Es link' to afternoon TEP.  There were single
hop Es before to Florida and afterwards to W3, W4 and W7."
"First LU on 6 Meters in solar cycle 24 for me."
Thank you, Jon.
Jeff Hartley, N8II of Shepherdstown, West Virginia wrote on May 19,
"I haven't been on the air much, but did manage to work the 7O6T
guys on 40 thru 15 meters, one QRP QSO near the end on 15 phone.
Signals were loud on 20 thru 15 most of the time in our evening.
The big operation stimulated quite a round of how to work a rare one
with big pile ups on the PVRC reflector.  Some DXers are obviously
masters of the art.  One tip I find very useful in spotting the
listening frequency on CW is to listen with a wide filter (over 2
kHz); it makes finding the DX station caller much easier.  Then try
to figure out which way they are tuning and follow along a bit
higher or lower depending on what direction they are tuning."
"I operated in the CQ M contest May 12th just about 2-1/2 hours and
found 20 meters to be very poor from 1200-1300Z, but 15 sounded good
with one of the loudest signals from UP0L.  On 20 in the evening
around 0200Z, there were loud signals from western Europe across to
Zone 18, but virtually all except EA's had heavy flutter, making
copying at high speeds difficult."
"It is Dayton weekend, so the bands should be abnormally quiet.  I
will try and make some noise."
This weekend is the CQ World Wide WPX Contest.  Conditions should be
fair, with unsettled but not terribly active geomagnetic conditions,
and low sunspot activity.
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 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 May 17 through 23 were 114, 118, 110, 124, 120,
95, and 91, with a mean of 110.3.  10.7 cm flux was 136.3, 132.2,
130.9, 130.8, 125.1, 121.3 and 117.2, with a mean of 127.7.
Estimated planetary A indices were 6, 8, 5, 13, 7, 16, and 18, with
a mean of 10.4.  Estimated mid-latitude A indices were 5, 8, 5, 12,
7, 15, and 13, with a mean of 9.3.


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