Register Account

Login Help

ARRL Propagation Bulletin ARLP030 (2011)

ARLP030 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 30  ARLP030
From Tad Cook, K7RA
Seattle, WA  July 29, 2011
To all radio amateurs 

ARLP030 Propagation de K7RA

Sunspot activity dipped over this past week, but now is on its way
back up.
On July 20, five sunspot groups were visible, but on July 21, only
groups 1251, 1254 and 1259 remained.  On July 24, new sunspot group
1260 appeared, and the next day 1251 disappeared.  On July 26 groups
1254 and 1259 went away, and new sunspot group 1261 arrived.  The
next day another new group, 1262 appeared, and on July 28 two new
sunspot groups, 1263 and 1264 appeared.  On July 28 the total area
of visible sunspots was greater than it has been since the end of
Average daily sunspot numbers for the week July 21-27 declined
nearly 47 points, a little over 50 percent, to 45.6.  Average daily
solar flux declined over 6 points to 91.8.
The latest forecast has been revised upward for solar activity
higher than was reported in this week's ARRL Letter.  The forecast
shows predicted solar flux at 110 on July 29 through August 4, 100
on August 5, 95 on August 6-7, 98 on August 8, and 100 on August
9-16.  It also shows planetary A index at 5 on July 29-30, 12 on
July 31 through August 1, 7 on August 2, 5 on August 3-4 followed by
12 again on August 5-7, and 8 on August 8-11.
Geophysical Institute Prague predicts quiet conditions on July 29,
quiet to unsettled July 30, unsettled July 31 and August 1, then
quiet to unsettled August 2 and quiet again on August 3-4.
Kent Reinke, KL1V reports some interesting VHF propagation on
Thursday, July 28.  He writes: "I live in Valdez, Alaska, and today
I had a very strange opening while I was driving home from Dawson
City Yukon.  I was 30 miles northwest of Tok Alaska on the 'Top of
the world highway' and while trying to pick up a local FM station
from Tok I was surprised to hear several stations and they were full
quieting with slow fade and after listening to them a few minutes I
found out they were all from Edmonton Alberta, which is a distance
of about 1235 miles.  There are several mountain ranges between
where I was and Edmonton.  The stations sounded like I was in
downtown Edmonton between the fades.  I only had my 2 meter radio
with a mag mount antenna but I did try a few calls on 146.52 simplex
but no one heard me.  The opening lasted 45 minutes and I was not
sure if it was ducting or sporadic E.  Next time I will have the 6
meter along".
Thanks, Kent.  Very interesting.
Bear Carson, AC7HI lives in Spokane in eastern Washington State and
wrote to ask about a "blackout" of radio signals he noticed
recently.  I sent his message to Randy Crews, W7TJ, who lives about
8 miles southeast of AC7HI.  Randy had these comments:
"You know if I could pick one month out of the year that I believe
is the worst for propagation in the Pacific Northwest, it would be
July.  Not so much QRN/Static, but flat East/West Propagation and
high summer D-layer absorption.
There have been exceptions over the years, however July seems to
always be the low point of the Summer.  Recently I noticed that all
HF propagation has really been down in the past few days even in
spite of increasing solar flux and sunspots plus a quiet geomagnetic
field, low dynamic pressure and solar wind plus magnetic field
oriented north, and small auroral ovals.
The big reason I can see is high X-ray flux, which will negate all
the propagation positives just mentioned.  What I noticed was 4
months of just stellar propagation starting in mid February of this
year and going until about mid June.
Recently two DXpeditions, ST0R and VK9HR have been extremely
difficult to copy.  The VK9 Group is on an island surrounded by salt
water and compared to the T31A group in April from Canton Island,
their signal on all bands has really been marginal.  With the recent
increase of solar flux they should be S-9 all the time.  So I would
attribute things to the lower solar flux vs. what we observed this
last spring, high D level absorption, and very high levels of X Ray
Flux.  I believe that in spite of all the satellites, scientific
equipment etc, propagation is still immensely complex".
Thanks, Randy!
Often we get email from non-hams who heard some piece of
contemporary folklore about threats to Earth from giant solar flares
or mysterious planets.  A recent article on covers this
well.  Thanks to N7SO for this.  Read it at
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, see the ARRL
Technical Information Service at  For an explanation of
the numbers used in this bulletin, see  An archive of
past propagation bulletins is at  Find more good
information and tutorials on propagation at
Monthly propagation charts between four USA regions and twelve
overseas locations are at
Instructions for starting or ending email distribution of ARRL
bulletins are at
Sunspot numbers for July 21 through 27 were 56, 54, 41, 46, 38, 30,
and 54, with a mean of 45.6.  10.7 cm flux was 96, 92.4, 88.2, 86.2,
87, 93.5, and 99.3, with a mean of 91.8.  Estimated planetary A
indices were 12, 10, 8, 4, 12, 5, and 4, with a mean of 7.9.
Estimated mid-latitude A indices were 10, 10, 6, 3, 10, 5, and 2,
with a mean of 6.6.


Instragram     Facebook     Twitter     YouTube     LinkedIn