Register Account

Login Help

ARRL Propagation Bulletin ARLP029 (2003)

ARLP029 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 29  ARLP029
From Tad Cook, K7RA
Seattle, WA  July 18, 2003
To all radio amateurs 

ARLP029 Propagation de K7RA

Stormy space weather returned this week. The average daily planetary
A index is over twice the value reported in last week's bulletin.
The quietest day was July 10, with a planetary A index of 8, and the
most active days were July 11, 12 and 16, when the planetary A index
was 46, 46 and 48.

The planetary A index is expected to quiet down for Friday, July 18,
then rise to 15, 20 and 25 for July 19-21. Solar flux is expected to
remain around 135 to 145 through the rest of July, with a somewhat
higher value possible on July 24.

On the morning of Saturday, July 12, earth was inside a strong solar
wind coming from a coronal hole on the sun. This was actually Friday
night in North America, and the resulting geomagnetic storm produced
auroras seen from Canada and the northern United States. Then on
July 16 another solar wind, weaker than the earlier one caused a
moderate geomagnetic storm, although the planetary A index was
marginally higher. The mid-latitude A index though was much lower on
July 16 compared to July 11.

Bill Hohnstein, K0HA wrote from Mississippi with an exciting story
about seeing a July 14 spot at 0002z for his 6-meter signal on a
European packet cluster. Milan, OK1FM posted the report which he
copied even though he had no 6-meter antenna. He was using a 40-10
meter multiband Yagi. Bill emailed Milan to confirm the spot, and
Milan emailed back with details on the antenna. Milan also said a
new five element 6-meter Yagi with an 18-foot boom is ready to go
up. See a picture of Milan and more about his station at

Serge Stroobandt, ON4BAA sent a link to a nice propagation web site
he put together, which among other features includes a MUF mapping
program that shows the Maximum Usable Frequency calculated in all
directions from any location. See it at, and you might want to make
sure your speakers and sound card are turned on.

Regarding recent comments about VHF propagation seemingly enhanced
during geomagnetic storms, Jon Jones, N0JK sent this quote from the
book, "Six Meters, A Guide to the Magic Band," by Ken Neubeck,
WB2AMU: "Geomagnetic storms appear to be a detrimental factor in the
formation of Sporadic-E. It is very rare for a Six Meter operator to
hear a strong Sporadic-E opening where there is high geomagnetic

For more information on propagation and an explanation of the
numbers used in this bulletin see the Propagation page on the ARRL
Web site at You can
write to the author of this bulletin via email at

Sunspot numbers for July 10 through 16 were 137, 127, 102, 137, 159,
154, and 164, with a mean of 140. 10.7 cm flux was 122.8, 122,
121.5, 126.5, 127.2, 125.8, and 133.1, with a mean of 125.6.
Estimated planetary A indices were 8, 46, 46, 14, 15, 27, and 48,
with a mean of 29.1.


Instragram     Facebook     Twitter     YouTube     LinkedIn