ARRL Propagation Bulletin ARLP027 (2005)

ARLP027 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 27  ARLP027
From Tad Cook, K7RA
Seattle, WA  July 1, 2005
To all radio amateurs 

ARLP027 Propagation de K7RA

Last weekend's Field Day exercise had better propagation than
predicted.  For several weeks, active geomagnetic conditions were
forecast for June 25-26.  But by late Friday afternoon in North
America that prediction had moderated somewhat.  Solar wind arrived
early, causing a geomagnetic storm on Thursday, June 23.  The
planetary K index shot up to 7, and planetary A index for that day
was 48.  Mid-latitude A index was 30.  Activity declined, and there
were no visible sunspots for several days.  Mid-latitude A index for
Saturday and Sunday, June 25-26 was 9 and 6 respectively.

Fifteen meters performed much better than expected, at least as
observed from the Pacific Northwest.  The K7RA Field Day operation
was very modest, operating Class C (Mobile) from a hilltop spot just
north of Seattle at a former missile site.  Operation was on SSB and
CW on 15 and 20 meters, and for just a few hours late Saturday
afternoon West Coast time.  Fifteen had surprisingly good
propagation to the Southeast United States, with many stations
contacted in Florida, Georgia, and Tennessee.

Dan Eskenazi, K7SS reported that six meters opened from the Seattle
area to the southwest U.S. just before Field Day's end on Sunday.
He was working stations in a swath from San Diego to Tucson, and
also found 10 meters active with sporadic-E skip.

Emory Gordy, W4WRO reported that the Silver Comet Amateur Radio
Society operating in North Georgia observed unusual propagation.
They only worked four stations on 15 meters, with 20 meters being
the productive band.  80 meter activity was the best he'd heard in
years.  They worked the West Coast quite easily, but didn't hear
much from Texas, Arizona, Utah, the Midwest, and worked very few
stations in Florida or Tennessee, and not one station in Kentucky.

Yesterday was the end of the second quarter of 2005, so let's look
at some quarterly averages to examine any trends.

From the first quarter of 2003 through the second quarter of 2005,
the average daily sunspot numbers were 120.3, 107.3, 110.2, 99.2,
72.9, 71.3, 69.3, 61, 46.1 and 55.7.

The average daily solar flux for the same period was 134.3, 124.2,
120.8, 137.4, 111.1, 99.5, 111, 104.8, 96.4 and 93.1.

Sunspot counts dropped during the first quarter of this year, but
recovered by nearly ten points during the second quarter.  So the
declining solar cycle is a general trend, but there is still a lot
of variation.  Solar flux dropped a few points over the same period.
This cycle is still expected to hit bottom around the end of 2006.

For the next few days, a solar wind stream should keep geomagnetic
activity higher.  Predicted planetary A index for Friday through
Monday, July 1-4 is 20, 20, 15 and 15.  Solar flux should rise over
the next few days, peaking around 115 from July 5-7.

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 23 through 29 were 19, 14, 12, 0, 11, 20
and 57 with a mean of 19. 10.7 cm flux was 77.5, 76.7, 76.7, 78.7,
77.4, 80 and 88.9, with a mean of 79.4. Estimated planetary A
indices were 48, 17, 11, 8, 4, 5 and 6 with a mean of 14.1.
Estimated mid-latitude A indices were 30, 7, 9, 6, 3, 3 and 4, with
a mean of 8.9.