ARRL Propagation Bulletin ARLP004 (2006)

ARLP004 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 4  ARLP004
From Tad Cook, K7RA
Seattle, WA  January 27, 2006
To all radio amateurs 

ARLP004 Propagation de K7RA

To recap the week's solar activity, the average daily sunspot number
rose nearly 25 points to 49.4, about double last week's count of
24.6. Average daily solar flux rose nearly 11 points to 91.4.

This week double-sunspot 848 continued to expand as it transited the
Earth-facing side of our nearest star. But by today, Friday, January
27, it is moving out of the sun's visible area. In the middle of
this week the interplanetary magnetic field moved south, and a
moderate solar wind drove the planetary A index to 29 on January 26.

By this time next year solar activity will probably be even lower
than now, with many days in succession with no visible sunspots. To
see what this is like, go back almost ten years to look at our
propagation bulletins in September 1996. You can find archives of
the old bulletins at and click on
propagation bulletins for 1996. Look at bulletins between 39 and 43
and you will see weeks of reports such as, sunspot numbers at "0, 0,
0, 0, 0, 0 and 0, with a mean of 0." These periods of low activity
aren't good for the higher HF bands, but can be great for 160 and 80

An email came in this week from Bill Gallier, W4WX, who writes that
he and K4QD are going to Ascension (ZD8) February 21-28. He wanted a
propagation prediction for 160 meters for those days to various
continents. But all of the popular propagation prediction software
is written around an algorithm that only works down to 3 MHz, and
not that well on the lower frequencies above 3 MHz. About the best
we could do was to recommend trying paths to various locations when
darkness is over both ends of the path. You can use a propagation
program like W6ELprop for this, because part of the prediction is a
listing showing the times for sunrise and sunset at both locations.
As always, you can find W6ELprop free at,

John Winans, WA2LGE wrote in asking about lists of beacons. I
googled a query and found one that is new to me at, Nice set of links to beacon
software and lists of beacons, from VLF to VHF.

For this week look for a planetary A index of around 12 for today,
January 27, and then 5 (very quiet) on every day through February 2.
Geophysical Institute Prague predicts unsettled activity for January
27, quiet to unsettled for January 28 and February 1 and 2, and
quiet conditions for January 29 to 31. Sunspot activity will remain
low, and the 10.7 cm solar flux is predicted around 85 for January
27-28 and 80 from January 29 through February 2.

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
propagation bulletins is found at,

Sunspot numbers for January 19 through 25 were 48, 33, 28, 60, 73,
62 and 42 with a mean of 49.4. 10.7 cm flux was 88.6, 90.7, 93.8,
92.8, 92.4, 92.6, and 89, with a mean of 91.4. Estimated planetary A
indices were 7, 6, 4, 6, 15, 7 and 7 with a mean of 7.4. Estimated
mid-latitude A indices were 5, 4, 4, 4, 13, 6 and 8, with a mean of