ARRL

ARRL Propagation Bulletin ARLP025 (2002)

SB PROP @ ARL $ARLP025
ARLP025 Propagation de K7VVV

ZCZC AP25
QST de W1AW  
Propagation Forecast Bulletin 25  ARLP025
From Tad Cook, K7VVV
Seattle, WA  June 21, 2002
To all radio amateurs 

SB PROP ARL ARLP025
ARLP025 Propagation de K7VVV

Field Day! This weekend is ARRL Field Day, possibly ham radio's most
popular organized operating activity. In the past this bulletin only
commented on domestic propagation for Field Day weekend, but this
year for the first time Field Day is expanded to cover all of the
Americas. The new rules say that anyone in IARU Region II may
participate, and this covers all of North, Central and South
America, Greenland, the Caribbean, as well as some Pacific Islands.
IARU Region II is the same as ITU Region II, and you can see a map
of Region II at, http://www.echelon.ca/iarumsr2/ituregions.html .

Remember that in Field Day there is no multiplier or extra credit
for number of states, sections, zones or countries worked. Contacts
with stations in all areas count the same. This distinguishes Field
Day from contests where top scorers pay close attention to working
the maximum number of multipliers. In Field Day multipliers and
extra credit are earned for operating low power, from batteries, and
for generating publicity for amateur radio's emergency preparedness
capabilities. See
http://www.arrl.org/contests/rules/2002/rules-fd-2002.html for
complete rules.

Solar flux and sunspot numbers declined again this week. The daily
average for sunspot numbers dropped by over 38 points and average
daily solar flux was down by 14 points compared to the previous
week, June 6-12. Solar flux reached a short term minimum last Friday
at 131.4, and is now on the rise. Current projections show it
peaking around 170 by the end of this month. The predicted flux
values for Field Day weekend, Friday through Sunday are 150, 155 and
155.

What we hope for this weekend and the days leading up to it are high
solar flux and low geomagnetic activity. Currently the earth sits in
a solar wind stream coming from a coronal hole on the sun. This
could possibly trigger high-latitude aurora, but the current
prediction for Saturday and Sunday is stable geomagnetic conditions.

One way to get a feel for conditions this weekend is to look at the
average Wednesday through Sunday solar flux (in this case solar flux
values for Friday though Sunday are the predicted numbers) and
Friday though Sunday average planetary A index for this year
compared to past Field Days. The 5 day solar flux average for 1998
through 2002 Field Days Are 111.6, 192, 177.3, 200.7 and 151.1. The
three-day planetary A index average for the same years is 19.3,
14.3, 16, 8.3 and 8.7. So in terms of the numbers, 2001 looks the
best, since it had both the highest solar flux and lowest
geomagnetic index.  If you compare some paths using a propagation
program such as W6ELprop (a new minor update version 2.61 is
available for free from http://www.qsl.net/w6elprop/ ) for the
numbers from 2001 compared to 1998, look at a domestic 15 meter path
from California to Ohio. You'll see a radical difference. But you'll
notice a slightly better path for 1998 on 40 meters.

In addition to being Field Day weekend, this is also the first
weekend of summer. This is not a great time for 10 meters, but check
10 meters for possible E-layer propagation rather than the better
F-layer propagation we see on this band in spring and fall. For
close-in propagation less than 1000 miles, your best band around the
clock will be 40 meters, and 80 meters after sunset.

W6ELprop was mentioned above, and also worth noting is the program
from KU5S, WinCAP Wizard 3. A 30 day trial version is available for
download at http://www.taborsoft.com/wwizard3 . Also at the
Taborsoft site is an excellent help file with propagation basics
written by NM7M.  Download it at the ''NM7M Tutorial - HF
Propagation'' link toward the middle of the web page. Also check out
''The Sun, the Earth, The Ionosphere'' on the ARRL web site at,
http://www.arrl.org/tis/info/k9la-prop.html . Another place to look
for propagation info is the ARRL Technical Information Service web
page devoted to the subject at,
http://www.arrl.org/tis/info/propagation.html .

Sunspot numbers for June 13 through 19 were 126, 102, 137, 132, 116,
174 and 127, with a mean of 130.6. 10.7 cm flux was 133.4, 131.4,
135.3, 136.7, 142.9, 142.9, and 145.8, with a mean of 138.3.
Estimated planetary A indices were 11, 7, 7, 11, 7, 11, and 16, with
a mean of 10.
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/EX