ARRL

ARRL Propagation Bulletin ARLP035 (2004)

SB PROP @ ARL $ARLP035
ARLP035 Propagation de K9LA

ZCZC AP35
QST de W1AW  
Propagation Forecast Bulletin 35  ARLP035
From Carl Luetzelschwab, K9LA
Ft Wayne, IN  August 27, 2004
To all radio amateurs 

SB PROP ARL ARLP035
ARLP035 Propagation de K9LA

Carl Luetzelschwab, K9LA is filling in for Tad Cook, K7RA this week.

This report covers the period Friday, August 20 through Thursday,
August 26.

Solar activity was at very low to low levels throughout the entire
period. The largest X-ray flare observed during the period was a
C2.8 flare on Friday. Solar activity is forecast to remain at low
levels over the weekend.

Geophysical activity over the period ranged from quiet to minor
storm. There were a couple of CMEs observed toward the end of the
period, but these didn't appear to be Earth-directed. Geophysical
activity is forecast to be quiet over the weekend.

Based on the forecasted solar activity and geophysical activity, we
shouldn't have any major surprises in propagation over the weekend.

Check out pages 5-25 in "The NEW Shortwave Propagation Handbook" by
George Jacobs, W3ASK, Theodore Cohen, N4XX and Robert Rose, K6GKU,
for the definitions of solar activity (very low, low, moderate,
etc.) in terms of X-ray events, and the definitions of geophysical
activity (quiet, unsettled, active, etc.) in terms of the K and A
indices.

A note from the Space Environment Center (SEC) and the U.S. Air
Force advises that the ACE (Advanced Composition Explorer)
spacecraft orbit will bring it closest to the Sun on Monday, August
30. During that time solar radio noise may interfere with spacecraft
telemetry resulting in the loss of real-time data - the data that is
shown on the 'dials' at http://sec.noaa.gov/SWN/index.html.

The April 30, 2004 Propagation bulletin mentioned the VOACAP Quick
Guide written by Jari Perkiomaki, OH6BG. This document is available
at http://elbert.its.bldrdoc.gov/hf.html.

The latest version (1 January 2004) contains many pertinent comments
about VOACAP (and propagation predictions in general) from George
Lane. Issues discussed are which ionospheric coefficients to use
(CCIR or URSI), erroneously using daily solar flux in propagation
predictions, comments about ICEPAC versus VOACAP, predictions on the
low bands (160 and 75/80 meters), take-off angles, operating above
the MUF, and several other important issues.

OH6BG also provides a list of the "Ten Common Mistakes in Using
VOACAP." George Lane's comments, along with OH6BG's list, are very
helpful in properly using VOACAP and understanding propagation
predictions in general.

For more information concerning propagation and an explanation of
the numbers used in this bulletin see the ARRL Technical Information
Service propagation page at,
http://www.arrl.org/tis/info/propagation.html.

Sunspot numbers for August 19 through 25 were 60, 85, 88, 102, 93,
55 and 60 with a mean of 77.6.  10.7 cm flux was 120.6, 121.4, 120,
115.2, 109.5, 104.9 and 100.4, with a mean of 113.1.  Estimated
planetary A indices were 7, 14, 17, 13, 7, 5 and 7, with a mean of
10.  Estimated mid-latitude A indices were 3, 9, 14, 8, 10, 3 and 3,
with a mean of 7.1.
NNNN
/EX