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ARRL Propagation Bulletin ARLP024 (2005)

ARLP024 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 24  ARLP024
From Tad Cook, K7RA
Seattle, WA  June 10, 2005
To all radio amateurs 

ARLP024 Propagation de K7RA

Sunspot and solar flux readings were up this week while geomagnetic
K and A indexes were down a bit, which is generally what HF
operators want. There were no big events triggering geomagnetic
storms this week, as indicated by the low A index numbers at the end
of this bulletin. A solar wind stream last weekend only drove
geomagnetic indices up to moderately active levels. But two big new
sunspots, 775 and 776, are rotating to the most effective position
for affecting earth. Solar flux for this weekend, June 10-12, is
expected to be around 110-115. Geomagnetic conditions should be
quiet, although the new sunspots are magnetically complex, and could
hold a surprise.

We're moving now toward summer propagation from the recent spring
conditions we've been experiencing. Summer solstice in the Northern
Hemisphere is set for June 21 at 0646z. Today we are 80 days past
the equinox, and the bands are behaving differently than they were a
few months ago. For instance, paths from the continental U.S. to
South America are open much later on 17 and 20 meters. You can run
two instances of W6ELprop, located on the web at,, and run some tests.

For instance, perform a test from the center of the Continental U.S.
(by entering W for the prefix) to Brazil for any date this week, and
enter an average of several days of sunspot numbers (from the end of
this bulletin). You can do the same for a date in late March, and
get the numbers from past bulletins at, Even though average sunspot numbers
were lower in late March than they've been this week, propagation
possibilities to Brazil during mid-day on 10, 12 and 15 meters in
March were much better than they are now. But signals over the same
path show better current openings much later into the evening on
those same bands than they were in late March. Plot from the central
U.S. to Hawaii as the target, and 20 meter signals drop out in the
evening in March, but are currently strong all night long.

The ARRL Contest Calendar, located at,, shows this weekend, June
11-13, is the ARRL June VHF QSO Party. The object is to get as many
contacts in as many grid squares as possible. Many HF radios these
days come with 6-meter capability, so it isn't much of a stretch for
HF operators without a 6-meter antenna to just toss up a dipole at
the last minute. A half-wave dipole is only about 9 feet and 3
inches long on 6-meters, and when the band opens up, a simple
antenna can do quite well. If you don't know your grid-square,
calculate it at If you hear
stations reporting unfamiliar grid squares, at least for the United
States there is a good map at You can find the
rules for the contest on the calendar mentioned above.

There have been many nice 6-meter openings recently, mostly via the
sporadic-E layer skip that is common this time of year, and Frank
Fascione, KB1LKB of Manchester, Connecticut sent in a report for
last Sunday, June 5. He reports an all day opening to the Caribbean
on 6-meters, as well as Georgia, Florida and Alabama. Among stations
heard but not worked were FG5FR, FM5JC, FM5AD, 9Y4AT, YU4DDK, and
PZ5RA. Frank contacted several new ones for him, including FJ5DX,

Doug, CO8DM uses 100 watts to a 2 element quad at 65 feet on 6
meters. He reports that around the first of the month he copied
European stations, including Italy and Sicily, and on CW, Malta.
The next morning he heard M0BJL in the UK.

Regarding the urging above to get on 6-meters, Eric Hall, K9GY wrote,
"... please mention for people to get on with their radios that can
work VHF and be active in the ARRL VHF contest. It doesn't take a
lot of stuff to make QSOs!" Eric made his first 6-meter QSO on June
5 with an FT-817 and a 6-meter Hamstick whip antenna. He was in FM18
and he worked N4OX in EM60 on 50.130 MHz SSB. Then he worked KA4DPF
in EM81 about 20 minutes later. People like me who are unfamiliar
with grid squares can look on the map mentioned above to see where
FM18, EM60 and EM81 are.

Bill VanAlstyne, W5WVO in DM65 seemed almost giddy about the opening
on Tuesday, May 31. He says it was "one of the most incredible 6M Es
openings I've ever been part of since moving to New Mexico a few
years ago. 6M was open from before 7 AM local time until nearly
midnight, with only a couple hours of rest around mid-day. I think
we're all still catching our collective breath from this one!"

Bill runs 100 watts to an 18 foot 5 element Yagi up 25 feet. He made
over 75 contacts and worked 13 new grids to boost his total above
300. He says he "ran pile-ups of calling stations for an hour at a
time like I was a DX station. Unbelievable! During the hottest
stretches, even QRP signals exceeded S9 +20 dB and were coming in
from all over the country at the same time, with path lengths all
the way from quite short (450 miles) to quite long (1800 miles)."

He continues, "No so-called 'double hop' here -- these east-coast
signals were as strong as those coming from half or a quarter of the
distance away. There were obviously a number of rather interesting
propagation modalities going on here. If only we really understood
this stuff!"

Bill has been a ham since 1962, and says "I don't think there is
ANYTHING more exciting than this kind of Es opening on 6M. It's
almost a transcendent experience!"

Nice to hear such enthusiasm. Maybe that's why 6-meter enthusiasts
call it "the magic band."

Currently we're two weeks away from Field Day. The long range
forecast from the U.S. Air Force shows a planetary A index of 20 (a
bit high) for both Saturday and Sunday of Field Day weekend, June
25-26. This is probably predicted because of coronal holes and solar
wind from the most recent rotation of the sun. Two weeks is a long
way off for predicting conditions, so we'll try to come up with a
more meaningful look in a couple of weeks.

If you would like to comment or have a tip, email the author at,

For more information concerning radio propagation and an explanation
of the numbers used in this bulletin see the ARRL Technical
Information Service propagation page at, An archive of past
bulletins is found at,

Sunspot numbers for June 2 through 8 were 69, 55, 74, 77, 89, 94 and
100 with a mean of 79.7. 10.7 cm flux was 93.3, 95.3, 96.9, 105.4,
106, 109.1 and 115.7, with a mean of 103.1. Estimated planetary A
indices were 7, 8, 18, 20, 13, 18 and 6 with a mean of 12.9.
Estimated mid-latitude A indices were 7, 10, 12, 14, 7, 11 and 3,
with a mean of 9.1.


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