ARRL Propagation Bulletin ARLP047 (2005)

ARLP047 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 47  ARLP047
From Tad Cook, K7RA
Seattle, WA  November 11, 2005
To all radio amateurs 

ARLP047 Propagation de K7RA

We may be in another period of zero sunspots. From October 24-28
there was a sunspot count of 0 on each day. Three days at the
beginning of the month were no-sunspot days, and four months ago
there were five days (July 18-22) with no spots. A year from now
expect to see longer periods of 0 sunspot readings, possibly up to
several weeks, based on what the periods between previous sunspot
cycles were like.

Earlier this month Propagation Forecast Bulletin ARLP042 (October 6)
referred to a nomograph, a graphic representation of numerical
relations, like a ruler calibrated with inches and centimeters.
This nomograph was supposed to illustrate the relationship between A
index and K index, such as the figures seen in the table at, Unfortunately, the
bulletin just quoted that same URL twice, but the unmentioned URL
(the one with the nomograph) can be found at,

Geomagnetic conditions should be fairly active for Friday. The
predicted planetary A index for Friday through Monday, November
11-14 is 15, 8, 5 and 5. The Prague Geophysical Institute predicts
unsettled to active conditions on November 11 and 12, unsettled
conditions on November 13, quiet to unsettled on November 14 and 15,
and quiet conditions November 16-17.

Remember that for good HF propagation we want these geomagnetic
numbers to be low, with sunspot numbers as high as possible.

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 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 November 3 through 9 were 24, 22, 18, 34, 31, 38
and 13 with a mean of 25.7. 10.7 cm flux was 76.8, 77.4, 79.3, 81.7,
79.4, 79.4, and 78.1, with a mean of 78.9. Estimated planetary A
indices were 24, 20, 10, 10, 6, 3 and 3 with a mean of 10.9.
Estimated mid-latitude A indices were 19, 16, 10, 12, 6, 2 and 1,
with a mean of 9.4.