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ARRL Propagation Bulletin ARLP022 (2005)

ARLP022 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 22  ARLP022
From Tad Cook, K7RA
Seattle, WA  May 27, 2005
To all radio amateurs 

ARLP022 Propagation de K7RA

To summarize the solar and geomagnetic numbers for the past week,
both were lower.  All days were quiet except for May 20, when
mid-latitude K and A index indicated unsettled geomagnetic
conditions and planetary numbers indicated a geomagnetic storm.

Check this site for the geomagnetic numbers:

You can see that every three hours there is a K index, and then a
resulting A index for the day.  May 24 had low K and A index.  On
May 20 you can see the numbers are much higher.  To see the
relationship between K and A index, check  According to this,
the planetary A index (or Ap) of 5 on May 24 would be equivalent to
24 hours of K index between 1 and 2.  Likewise on May 15 the Ap of
105 is equivalent to 24 hours of K between 6 and 7.

Average daily sunspot numbers this week were down over 39 points to
36.6, and average daily solar flux dropped over 19 points to 83.5.

Today and tomorrow, May 27 and 28, a solar wind stream from a
coronal hole is expected to affect earth.  Predicted planetary A
index for May 27-30 is 10, 20, 20 and 12.  Solar flux is expected to
rise slowly, reaching 100 around May 29 and peaking around 105
around June 3 and again on June 7-10.

None of this should have a major negative effect on the CQ World
Wide WPX CW Contest this weekend.

Readers sent links to several articles of interest to amateur radio
propagation watchers this week:

More six meter news dropped in over the week.  Larry Bishop, KB9WLM
of Canton, Illinois wrote to report that on May 17 2005 he worked
Korean station HK2JRL at 2320 UTC on 50.135 MHz.  Larry has a rather
impressive 6 meter antenna.  He ran 375 watts into a homebrew 6
element Yagi with a 34 foot, 8 inch boom at 125 feet fed with hard
line.  Chuck DiLuglio, K1DA in Jamestown, Rhode Island on late
Tuesday (probably early May 18 UTC) worked five or six stations in
Indiana and Minnesota barefoot with a rotating dipole.  He wrote,
''The interesting thing is that no other states were heard here in
FN 41 but those two so it was a very localized opening.  Signals
were very strong.''  Mike Williams, W4DL was on six during the same
evening near Fort Lauderdale, Florida.  Mike wrote, ''I was handily
working into the Caribbean and Central America on phone and then
switched to CW and the band was wild. QRM on 6 CW; I love it. Stayed
up until I had enough and the lower latitudes were still rolling in
around 10 PM local time.  Using 50 watts and 4 elements pointed
south with the rad center at 20 feet.  There are significantly more
operators on 6 down here in south Florida than in years past.
Enough of us now to use it for local chatting between listening for
the openings.''

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 May 19 through 25 were 34, 22, 37, 42, 36, 40
and 45 with a mean of 36.6. 10.7 cm flux was 84.7, 83.5, 81.9, 82.1,
83.4, 85.2 and 83.8, with a mean of 83.5. Estimated planetary A
indices were 11, 30, 21, 14, 7, 5 and 6 with a mean of 13.4.
Estimated mid-latitude A indices were 7, 17, 13, 10, 5, 2 and 2,
with a mean of 8.  


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