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ARRL Propagation Bulletin ARLP019 (2011)

ARLP019 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 19  ARLP019
From Tad Cook, K7RA
Seattle, WA  May 13, 2011
To all radio amateurs 

ARLP019 Propagation de K7RA

As reported in the ARRL Letter, on Wednesday May 11 six sunspot
groups were visible, but that number shrunk to two on Thursday.
Daily sunspot numbers declined from 84 to 29 over those two days as
well, but the average sunspot number for the reporting week
(Thursday, May 5 through Wednesday, May 11) grew by nearly 7 points
from last week to 74.6.

The latest forecast shows planetary A index of 10 for today, May 13,
then 8 on May 14-16, 10 on May 17, 8 on May 18, and 5 on May 19-25.
The next possibly big geomagnetic period is May 27, with a planetary
A index of 22.

The same forecast predicts solar flux of 95 on May 13-14, 90 on May
15-19, and 110 on May 20-30.

Geophysical Institute Prague predicts quiet to unsettled conditions
May 13, quiet May 14, quiet to unsettled May 15, unsettled May
16-18, and quiet to unsettled again on May 19.

On May 9 NASA released a slightly revised prediction for the peak of
Cycle 24, placing it at a smoothed sunspot number of 69 in June
2013.  But a month earlier the estimate had a peak of 62 in July
2013.  Last month NASA was predicting this cycle as the weakest in
200 years, but the update places it as the weakest in the last

These are Zurich sunspot numbers, which are always quite a bit lower
than the NOAA SESC numbers that we report here.  The NOAA numbers
show a peak at 90 around February through July 2013.

On May 10, Rol Anders, K3RA of Elkridge, Maryland wrote, "After a
slow week or so, propagation has rebounded with extremely strong
signals from Europe and Central Asia on 20 meters for several hours
after their sunrise time. Many 30 and 40 dB over signals heard in
Maryland.  I think there have been a lot of tardy arrivals at work
in EU and Central Asia as the hams have had difficulty pulling
themselves away from such great conditions in the morning! Also, 17
meters has been very good in the evening with JAs and other Asian
stations coming back to CQs 3 hours after sunset on the East Coast.
15 meters has been open to the Far East after sunset as well.  Most
interesting was working JQ1QKK short path on 20 meter phone at 3 pm
his time, 2 AM east coast time!

"One 'trick' that I sometimes use to find openings is to look for
'analogous openings' at my latitude. If I can work a DX station
close to my latitude at a certain time of the day, then it is likely
that I'll be able to work stations at that latitude the same
distance away in the other direction when my local time is the same
as that first DX station's was. Perhaps this is best explained by an
example: the latitudes of JA and EX/EY/EZ/YA are not too different
from Maryland, and they are both roughly the same distance away from
me.  So, if JQ1QKK in the example above was working me at 3 pm his
time (2 am my time), there should be an opening to the general
EX/EY/EZ area from MD at 3 pm my time, 2 am EX/EY/EX time. This can
be extended to other latitudes if you know what DX stations at your
latitude are working. For instance, if I hear stations at my rough
latitude (EA, I, SV, EX, JA) working a path, I should have that same
path when my local time is the same as theirs was when they
experienced those paths. Of course, my path will be to an entirely
different part of the world."

Mark Bell, K3MSB of Airville, Pennsylvania wrote, "Had some nice 6M
sporadic-E action here around May 3. Worked YV4DYJ in FK50 at 2253Z.
Stations from LU were coming in quite strong the next two days."

N0JK reports from Kansas that on May 5 he worked LU4FW on 6 meters
with a sporadic-E trans-equatorial link. It was at 2138z, and he was
using an indoor dipole.

Rich Molinski, WB2KWF of Smithfield, Virginia reported from FM16qw
that on May 2 he worked 9Y4D and YV4DYJ on 6 meters using 80 watts
and a 3 element beam at 35 feet, with 5x3 reports each way.  On May
6 he reported, "I was amazed at the propagation! It's nice to see 6m
open up. Each night this week, 6 has been open to some degree."

Bob Elek, W3HKK in central Ohio reports an E-skip opening on May 5
on 6 meters. He reports, "A C6 was 59+20 and had half the US calling
him on SSB.  Then for the first time in my 55 year ham radio career:
TE skip to Argentina!  (Interestingly I had just finished reading
the VHF column in CQ Magazine describing how May was the poorest
month for TE skip and not to expect it.) Well, around dinner time in
Ohio, on May 5th there it was. The 6M band literally teeming with
Argentine stations, mostly on SSB, from 50.1 to 50.13 MHz.  LU after
LU working pile ups, calling CQ, and coming in between 5x3 to 5x9
(on my 5 el Yagi, 10 ft above my rear patio, equipped with the
standard Armstrong rotator, and fed by an IC7600 100w rig).

"At 2125z I worked LW3EX on 50.101 CW, then at 2133 9Y4VUX on 50.100
CW, and then at 2200z LU9EEM on 50.120 SSB, all with sigs between 57
and 59! In between I tuned around for other countries and passed up
on many LUs. Another local op worked the VP8 (Falkland Islands), and
a couple spots showed one station in OA and CE coming through but I
didn't hear them.

"So, in summary, a very telescopic opening via TE into Argentina lit
up 6M, and when things quieted down at around 2230z, I left for
dinner a little late but a very happy camper."

Roger Gibson, K4KLK of Raleigh, North Carolina (in FM05) reports,
"Six was open all day May 5 to WI area and then FL. I was surprised
to hear LU4FW FF97 on halo antenna in garage. I quickly turned
antenna south then connected the 4 El Quad 20 feet up and got him on
first call with 100 watts. Not many takers but signal was very
strong 59+ more like F2 and no fading. Contact made on 50.125 SSB at
2200Z. He was in for several minutes."

Both K5LJ and N4ZQ wonder why it seems that most sunspots appear in
the Sun's northern hemisphere so far in this cycle.  I ran this by
K9LA who says, "Hemispherical asymmetry of sunspots has been known
and studied for quite a while. I don't think there's an air-tight
explanation yet, but it is tied to the Sun's conveyor belt.  So
what's happening now is 'normal' in the sense that it's been seen
before in other cycles."  He noted that butterfly diagrams of Cycle
20 show this predominance toward the beginning of the cycle, around

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 May 5 through 11 were 95, 71, 38, 61, 93, 80,
and 84, with a mean of 74.6. 10.7 cm flux was 104.9, 101.9, 102.2,
102.2, 103.7, 97.5, and 94.1, with a mean of 100.9. Estimated
planetary A indices were 7, 4, 4, 2, 3, 8, and 6, with a mean of
4.9. Estimated mid-latitude A indices were 5, 3, 3, 0, 2, 5, and 7,
with a mean of 3.6.


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