ARRL Propagation Bulletin ARLP003 (2008)

ARLP003 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 3  ARLP003
From Tad Cook, K7RA
Seattle, WA  January 18, 2008
To all radio amateurs 

ARLP003 Propagation de K7RA

We've seen another seven days with no sunspots.  After observing the
first sunspot of Cycle 24, we hope to see more and more of these,
signaling the beginning of the next sunspot cycle and the end of
Cycle 23.

Dick Gird, K6PZE of San Diego, California wrote asking how to
distinguish Cycle 24 sunspots from Cycle 23 spots.  There are two
features that differentiate spots from each cycle.  Old Cycle 23
spots will appear near the Sun's equator.  The first spots of Cycle
24 are at a high solar latitude, and will have magnetic polarity
opposite of the old spots.  Last week there was a brief appearance
on January 11 by an almost-sunspot which disappeared by the
following day.  It appeared to be a Cycle 24 spot, which had
polarity reversed from Cycle 23 spots, but it was near the equator,
which is the wrong place for a new cycle sunspot.

Tom Schuessler, N5HYP of Irving, Texas wrote to ask about the
differences between the geomagnetic A and K index.  He asks, "I know
that both of them are indications of the instability of the
geomagnetic field.  The K index is logarithmic and the A index is
linear, and they track together -- kind of.  K indexes are given
every three hours while A index readings are for a full 24 hour
period.  Do the two indexes have different uses or tell a person
different things about what to expect on the air?"

Based on three hours of magnetic data, a particular magnetometer or
group of them is used to track the change in nanoTeslas, which are
the international units for measuring magnetic flux density.  K
index is based on changes in the flux density over a 3 hour period,
and the difference between the highest and lowest values at the
magnetometer is converted to a semi-logarithmic scale that runs from
0 to 9, yielding a K index between 0 (very quiet) and 9 (extreme
magnetic storm).

An example is the latest Boulder K index, as reported by WWV at,  Note at the end of the line giving K
index is a nanoTesla (nT) reading.  At the end of a UTC day
(midnight in Greenwich Mean Time) a new A index is reported, based
on the latest eight K index values.  A nomograph showing the
relationship between A and K index is at,
Note that if you have K indexes for one day averaging 2, the A index
for that day would be 7.  But if the average were 3, this
corresponds to an A index of 15, and an average of 4 equals 27.  You
can see a table of three different A and K index readings at, .

They are both derived from the same magnetic readings, but the A
index is for a whole day, and has an expanded scale.  When those
numbers are low, we expect less absorption and in general better
propagation of radio waves.  But sometimes high geomagnetic activity
can signal improved VHF conditions, allowing distant propagation of
6 meter signals, for instance.  Because there is a new K index every
three hours, this gives us a more immediate indication if conditions
are changing fast.  So if WWV reports a K index of 2, then three
hours later reports a K index of 5, this indicates a dramatic event,
such as an earth-directed solar flare, or a blast of strong solar
wind, and a resulting geomagnetic storm.

Josh Sawyer, a shortwave listener, wrote, "The sunspot minimum such
as in 2007 and 1986 seems to yield the best conditions for working
far away DX on the 80 and 160 meter bands, and at the same time the
worst conditions when 15 and 10 meters are dead. Does this mean
lower frequency bands such as 80 and 160 meters don't use ionized
F-layers or sunspots at all during these lows, that its just real
far E layer or groundwave and we can work these stations because
it's the period of minimum noise generated by the Sun?"

160 and 80 signals do propagate through the F layer.  During
daylight most of the RF energy is absorbed by the ionosphere's D
layer, but at night the D layer disappears, and 160 and 80 meter
signals can be refracted off the ionosphere.  But it doesn't take
much ionization at those low frequencies to propagate signals.  The
more energy charges the ionosphere, the denser it becomes, and it
will refract higher and higher frequencies.  That is why the MUF
(Maximum Usable Frequency) increases as sunspot numbers go up.

With zero sunspots on January 16th, early in the morning (West Coast
Time) the MUF is at a minimum, 10 MHz, between San Diego and
Australia, as an example.  So that supports 160, 80 and 40 meter

MUF is calculated for a specific path at a specific time and season.
If you download W6ELprop (free at you
can try out difference scenarios.  If you change the sunspot number
from 0 to 150, and change the date to March 16 instead of January
16, instead of the MUF varying throughout the day between 10.1 and
24 MHz, it ranges from 20.4 to 47.4 MHz over that same San Diego to
Australia path.

This program can also be used to get an idea how a band will change
through the season over a particular path.  For instance, if we take
the more pessimistic smoothed sunspot number of 3 predicted for
January and plug it into a San Diego to New Zealand path for January
18, we see the MUF minimum of 9 MHz at 1330z and maximum MUF of 21.3
MHz at 0100z.  The best bet for 20 meter propagation is a brief
period with declining signal strength around 1600-1800z.

We can run the same path two months later on March 18 using the
slightly more optimistic projection for smoothed sunspot number of
4.  This time the lowest MUF is 10.7 MHz at 1300-1330z, and maximum
MUF for the day is 25.7 MHz at 0100-0130z.  The best 20 meter
propagation would be around 0230-0530z.

Pat Dyer, WA5IYX of San Antonio, Texas, sent interesting comments
about a couple of items in last week's Propagation Forecast Bulletin

He wrote, "As you mention, for over 40 years I'd read that a
(sunspot) cycle began when the number of new and old cycle groups
became equal . . .  it was on a Radio Switzerland broadcast that I
heard that the first Cycle 20 group had been observed in August 1962
-- some two years before the July 1964 minimum!"

Pat commented on the N0JK observation regarding why Winter and
off-season E-skip is more likely in the evening, but Summer E-skip
seems more frequent in the morning.

Pat wrote, "One reason for the after-dark preference for Winter Es
(suggested by E.K. Smith in 1968) might be an inhibiting effect of
(high) conductivity in the normal E-layer at the magnetic conjugate
point (where the earth's magnetic field lines return in the opposite
hemisphere).  It was also suggested that this might explain the
'double hump' diurnal for the Summer Es pattern."

Pat provided an article and several illustrations regarding 6 meter
E-skip linked from,, , and  He has other interesting material at, .

Last weekend Jeff Hartley, N8II of Shepherdsville, West Virginia
wrote about improved conditions over the previous weekend.  Jeff
wrote, "Just a quick note that HF condx on ALL bands except maybe 28
MHz were markedly improved last weekend, Jan 4-6. I worked loud
Scandinavians, UA3/4, 4O3A, ZB2FK, HB0, MJ, EL2DX, ZP6CW and
OA4/N6XQ on 160M. 15 was wide open to EU and snagged CT2 on 12M at
1545Z Sat."

Also from the previous week, Jon Jones, N0JK of Wichita, Kansas
wrote, "Two major 6 Meter Es openings this week - on January 8 and
again on the 9th. The 8th was across the Midwest - KS, OK, NE to TN,
VA, PA, etc. KC0CF IA worked KP4EIT PR on double hop Es. On the 9th
some double hop in the afternoon of January 9. VE1YX FN74 heard the
N0LL/b EM09 at 2,830 km. Open for over 4 hours from VE1, 1, 2 to
VE4, 0 and 9. I had a nice QSO with K2PS FM29 at 2140 UTC."

Sam Sitton, W5CU of Edmond, Oklahoma wrote concerning 80 meters,
saying, "I noticed the report you received about excellent band
conditions for short path to Europe on Jan. 3rd. Apparently, these
conditions were present again on the night of Jan. 9th, around 7:00
p.m. local time, when our 80 meter (3.552 MHz) NTS section traffic
net (TEX CW net) enjoyed having a check-in from Gary CU2JT. Gary
lives on Sao Miguel Island in the Azores, about 3800 miles distant
from my Oklahoma QTH according to my logging software. Following the
close of the net, Gary exchanged contacts with me and other net
members, with a 569 signal throughout. He was stronger here than
most of the Texas stations!"

Also regarding the low end of the spectrum, Tim Prosser, KT8K of Ann
Arbor, Michigan wrote, "For many mornings now, on my way to work in
Dearborn, MI, before local dawn, the clear channel station on 950AM
(WWJ) has been too 'long' to pick up well from my home in Ann Arbor,
about 25-30 miles away.  In fact, I could barely hear it, and it
usually sounds like backscatter, almost drowned out by a mishmash of
distant signals, until I am 10 or even 5 miles from Detroit."

He continues, "Also, 40 meters has been 'going out' nightly, with
poor conditions by 9 or 10 PM and sometimes even earlier.  30 meters
has been closing out almost completely by a couple of hours after
sundown.  And I, too, have heard EU stations booming in on 80m at
unusual times."

He ends with, "I'm so glad I put that 20/40/80m fan dipole up at 60'
last year!"

To read more about Tim's adventures with low power and low antennas,
check his profile at,

Jack Campbell, KZ4USA of Bradenton, Florida using an inverted vee on
160 meters heard Japanese stations on January 9 at 1200z.

So what do conditions look like over the next week?  Expect quiet
geomagnetic conditions through the end of this month, with the next
geomagnetic disturbance centered on February 1.  We may see sunspots
return January 28 through February 3.

Geophysical Institute Prague predicts quiet to unsettled conditions
January 18-19, and quiet conditions January 20-24.

Finally, to end this bulletin I would like to mention Vern Buttenob,
K7AYE.  He served in the Army Signal Corps in World War II, and I
believe much of his HF activity as a ham was during the 1950s, when
he experienced the thrill of sunspot Cycle 19, the biggest sunspot
cycle and the greatest HF radio propagation of all time.

In 1963 when we first met, I was 11 years old, and attended grade
school with his son Bill.  Vern was an engineer for the local Bell
company, and lived through the woods and up the hill from me.  When
I built my first shortwave receiver that year, a Knight Kit Star
Roamer, he spent the better part of a weekend patiently correcting
my many wiring errors and fixing the cold solder joints to get it
working.  Then when I was 12, after having delivered his newspaper
and many others long enough to put together a little cash for a used
CW transmitter, he proctored my Novice exam, and I became WN7CSK.

Mr. Buttenob, as I called him when I was a lad, passed away at the
age of 85 on New Year's Eve.  Last year I sent him an email, but
when I didn't receive a reply, I thought he might be ill.  Last
Saturday I had the privilege of attending his memorial, along with
his many friends and family members, where I learned many details of
a rich and full life, lived by a man who was loved by many.  73

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 a detailed
explanation of the numbers used in this bulletin see,  An archive of past
propagation bulletins is at, .
Monthly propagation charts between four USA regions and twelve
overseas locations are at .

Sunspot numbers for January 10 through 16 were 0, 0, 0, 0, 0, 0 and
0 with a mean of 0.  10.7 cm flux was 75.7, 76, 75.7, 75.3, 75.6,
73.7, and 72.9 with a mean of 75.  Estimated planetary A indices
were 3, 2, 9, 11, 16, 8 and 11 with a mean of 8.6.  Estimated
mid-latitude A indices were 2, 2, 4, 9, 14, 7 and 9, with a mean of