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ARRL Propagation Bulletin ARLP041 (2004)

ARLP041 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 41  ARLP041
From Tad Cook, K7RA
Seattle, WA  October 8, 2004
To all radio amateurs 

ARLP041 Propagation de K7RA

More mail this week about 10-meters and using beacons to detect band
openings, but first let's look at the numbers.

Average daily sunspot numbers rose this week from last, jumping over
17 points to 38.1. Average daily solar flux was about the same.
Solar activity has been very low, and fortunately geomagnetic
indices are also low as well. Don't expect a change over the next
few days, but a slight increase in solar flux is predicted for
October 15-16, when it may rise to around 105. Otherwise, until then
expect low sunspot numbers, and solar flux around 90-95.

Geomagnetic activity should continue to be quiet, but there is a
chance of some unsettled to active conditions around October 12-15.
Currently the visible sun is nearly spotless, but helioseismic
holography reveals a sunspot group on the sun's far side. The sun
rotates relative to earth about every 27.5 days, so it will face us
later this month.

Now that the third quarter of 2004 has passed we can review
quarterly averages for sunspot numbers and solar flux.

From the third quarter of 2002 through the third quarter of 2004,
the average daily sunspot numbers were 193.5, 152.7, 120.3, 107.3,
110.2, 99.2, 72.9, 71.3 and 69.3. The average daily solar flux for
the same period was 178.1, 164.2, 134.3, 124.2, 120.8, 137.4, 111.1,
99.5 and 111. Yet more evidence of cycle 23's slide toward solar
minimum, currently forecast to occur a little over two years from

Geoff, GM4ESD wrote with more comments about copying African beacon
stations on 10-meters from Scotland. Geoff wrote, "I am not at all
certain that the summertime propagation mode is 'classic' multi-hop
F2 during the 1100-1400z slot. Unless there is sporadic E about the
same time, none of the beacons at [an] estimated one hop F2 distance
from here toward ZS6DN are heard. When there is sporadic E about,
ZS6DN tends to be much weaker, if heard at all, regardless of the
location of the E 'cloud'. Only in the evening does sporadic E
appear to help. Very often during this 1100-1400z slot ZS6DN's
signal has a slight watery sound, but not as severe as on a 6-metre
transcontinental signal."

Geoff goes on to say, "I have never heard an echo. I would have
thought that I am a bit too far north for direct Trans-Equatorial
Propagation, as we understand it to be involved so frequently during
this time of day. If there is a 'classic' F2 opening between South
Africa and here, most times I hear the ZS1J beacon as well, or ZS1J
without ZS6DN. ZS6DN is not appearing so often after the equinox,
either at 1100-1400z or at 1600-1700z. I suspect the 'rules' of
solar flux/sunspot numbers are taking over, and now he only appears
if there is a 'classic' multi-hop F2 path open to him."

Junji Saito, JA7SSB sent an email pointing out a typo in last week's
bulletin, where I wrote that the solar flux was expected to reach
200 by October 7. He guessed correctly when he said 100. (KK4TA
noticed as well, and also guessed the valid number correctly). In
fact, the three daily readings at the Penticton observatory in
British Columbia for October 7 were a bit lower at 91.4, 93.8 and
94.9. Those readings are taken daily at 1700, 2000 and 2300z, but
the local noon reading at 2000z is always the official solar flux
for the day.

Junji had other comments, in addition to politely correcting the
predicted solar flux number. He said this Autumn he experiences good
daily 20 meter propagation to North America around 0200-0600z, and
he uses both SSB and RTTY. I expect he gets great propagation to the
West Coast.

Here in the Pacific Northwest, Japan is often loud, and depending on
conditions, sometimes pileups of JA calls respond when calling CQ
with a good signal toward that direction. A reminder of this was
when Henry Platt, W3UI visited Seattle last week. The bed and
breakfast he stayed at was only a few blocks from Dan Eskenazi,
K7SS. Dan has a great shot to the Pacific from his house on a high
spot in West Seattle, with a commanding view of Puget Sound. His
back yard ends at a cliff which drops off toward the west, a quarter
mile from salt water. Henry loves CW, and couldn't resist getting on
the air. He was amazed at the multitude of JA signals and how many
other Pacific stations he could work from Dan's station.  Of course
at home in Eastern Pennsylvania, Henry easily works Europe, but the
path toward Japan is much further and polar as well.  A polar path
has the disadvantage of being poor for HF propagation when
geomagnetic indices are high. Dan works Japan easily, but Europe is
a polar path for him.

Thomas Giella, KN4LF wants to remind us of the propagation email
reflector mentioned in this bulletin eight weeks ago. You can sign
up at,

Finally, Joe Pontek, K8JP in Indiana writes about working 6-meters
from Central America in Belize. When he is there and signing V3, he
often listens in the evening for South America. When he hears U.S.
stations on backscatter, he calls them, but when they turn their
beams toward him the signals are gone. He said this is particularly
true with Florida stations. For an interesting web article on
backscatter, see

If you would like to comment or have a tip, email the author at,

For more information concerning propagation and an explanation of
the numbers used in this bulletin see the ARRL Technical Information
Service propagation page at,

Sunspot numbers for September 30 through October 6 were 36, 37, 35,
39, 41, 40 and 39 with a mean of 38.1. 10.7 cm flux was 88.2, 88,
88, 89, 90.7, 90.8 and 92.1, with a mean of 89.5. Estimated
planetary A indices were 4, 4, 12, 15, 10, 5 and 5, with a mean of
7.9. Estimated mid-latitude A indices were 2, 2, 8, 7, 8, 3 and 2,
with a mean of 4.6.


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