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ARRL Propagation Bulletin ARLP033 (2023)

ARLP033 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 33  ARLP033
From Tad Cook, K7RA
Seattle, WA  August 18, 2023
To all radio amateurs 

ARLP033 Propagation de K7RA

Eleven new sunspot groups emerged over the past week, August 10-16,
but average solar indicators declined.

There were two new sunspots groups on August 11, three more on
August 13, another on August 14, two more on August 15, and three
more on August 16. On August 17 another new one appeared.

But average daily sunspot numbers declined from 108.9 to 95.7, while
average daily solar flux dropped from 166.4 to 154.2.

Predicted solar flux is 150, 155, and 157 on August 18-20, 160 on
August 21-22, then 162, 165, 162, 160 and 164 on August 23-27, 168
on August 28-31, then 165, 163 and 160 on September 1-3, then 158,
155, 152 and 150 on September 4-7, and 148, 142, 140 and 130 on
September 8-11, 135 on September 12-14, and 145, 150, 155, 158 and
160 on September 15-19, 162 on September 20-21, then 160 and 164 on
September 22-23, and 168 on September 24-27.

Predicted planetary A index is 12 and 8 on August 18-19, 5 on August
20-25, 12 on August 26, 5 on August 27 through September 5, then 10,
8 and 8 on September 6-8, 5 on September 9-11, then 12, 15, 12 and 8
on September 12-15, 5 on September 16-21, 12 on September 22, and 5
on September 23 through the end of the month.

Weekly Commentary on the Sun, the Magnetosphere, and the Earth's
Ionosphere August 18-24, 2023 from OK1HH:

"Solar activity has declined, both spot and flare. We have usually
observed C-class solar flares, although the configurations of some
active regions did not preclude the formation of M-class flares. We
expect an upsurge in solar activity in the last five days of August,
after which more sunspot groups should appear at the eastern limb of
the solar disk.

The Earth's ionosphere was quite sensitive to the increased influx
of protons in the accelerated solar wind on 11 August and again on
16-17 August. Propagation improved on August 14-15 and worsened on
August 16. I do not expect any other surprises before the end of the

Bil Paul, KD6JUI, who often reports HF operations from his kayak,

"I recently returned from a vacation at Lake Tahoe where I was
running 10 watts into an end-fed half-wave wire vertical. The rental
place was surrounded by extra-tall pine trees, but the base of the
antenna was 30 feet above the ground on a high porch.

My discovery (on the evenings of August 7 and 9, around 8 p.m.
Pacific Coast time) was that CW DX was coming in on the 30-meter
band. On the 7th, I contacted OV1CDX in Denmark on that band (and
heard him again on subsequent nights). On the 9th, I contacted 6B2A
in Egypt, who was coming in a solid S4.

I had a couple other CW DX twilight/early-night contacts on 15 and
20 meters, but the 30 meter contacts surprised me."

N4KZ reports from Frankfort, Kentucky:

"Last week, I began copying SSB signals from Europe on the 10 and
12-meter bands.  They were weak but readable. It was the first time
I've heard SSB signals on those bands from that part of the world in
many months. Then, on August 15th beginning at 1248 UTC, I worked
stations across Europe and the Middle East on 12-meter SSB with
strong signals.

About 20 minutes earlier, I tuned across the 10-meter phone band and
only copied one signal. It was S79VU, Ravi, in the Seychelles. He
was about S5 and working Europeans who I did not copy. But he came
back to me on my first call. We've worked before but this was our
first 10-meter QSO. It's only mid-August, but perhaps autumn
propagation is beginning to emerge and with the continuing high
sunspot count, I hope this marks the start of better HF conditions
this fall and winter. I run about 800 watts into a multi-band Yagi
with 3 active elements on each band. The antenna is up 55 feet. I
live on a hilltop with a steep slope toward the north which has
proven over the years to be an advantage.

On July 1, I once again became active on the low-end of 2 meters
doing weak-signal work. I was quite active on SSB and CW on the low
end throughout the 1980s and '90s and to a lesser extent until about
2010. I worked 40 states from Kentucky but eventually decided to
concentrate on HF and 6 meters. But I missed 2 meters and now I have

There's less SSB and CW than there used to be but quite a few are
operating FT8 on 144.174 MHz which does a nice job with weak
signals. So far I have worked 15 states and Ontario. Morning
propagation a couple hours after sunrise allows for 300-400 mile
QSOs routinely on FT8. And I've copied stations from Colorado, Long
Island, NY and Connecticut on meteor scatter while using MSK144.
After a 12-year hiatus from 2-meter weak-signal work, it's good to
be back."

AA6XE in Fremont, California wrote:

"Interesting conditions on 10 meters although not that unusual. In
the last couple of days propagation into the Pacific Northwest has
materialized. A bunch of Beacons have surfaced. Beacons from
Portland to well north of Vancouver BC are coming in every
afternoon. I heard Tad Cook's (K7RA) 10 meter beacon yesterday (Aug
13). Beacons out of Mexico have been coming in on 10 Meters for over
a month. Some of those beacons are located as far South as Veracruz.
Beacons from Australia have been coming through on most days over
the last month. NCDXF beacons VK6RBP in Western Australia and 4S7B
in Sri Lanka were heard on 15 Meters for a few days.

While propagation on 10 to the Pacific Northwest may not seem like
much I recognize it as a marker that the days of summer propagation
are numbered. Typically this doesn't happen until the last 2 weeks
in August so it appears to be early this year. So like the Crocuses
popping up in late February it doesn't do much for one aside from
reminding us that better times are on the way.

As to what we can expect this Fall it looks to be much improved over
last year and at the peak of Cycle 24. The 90 day mean SFI currently
stands at 166. Last year at this time 90 day mean stood at 114. The
90 day Mean SFI for the peak of Solar Cycle 24 was 155.  The 90 Day
Mean made a significant run-up during late Spring early Summer
increasing 21 points. For the last 5 weeks the Daily SFI has been
sliding. It hasn't dropped enough to impact the 90 and 81 Day Mean
Values just yet, but if the decline continues those numbers will

The rising phase of SC25 has its own characteristics. The solar flux
rises rapidly for 4 to 8 weeks followed by an extended period of
decline for 2 to 3 months. This makes it difficult to see the
overall trend. It even faked out a number of heliophysicists who
made the call that SC 25 had peaked in February 2023. The latest
predictions call for SC 25 to peak at year-end 2023/2024. A few are
calling for SC 25 to peak at mid-year 2024. It would be a pleasant
surprise if the next surge kicks off a few weeks early, say by the
first days of September. That would make a big impact of the
conditions we can expect on 6 Meters this Fall."

The latest from Tamitha Skov:

Send your tips, reports, observations, questions and comments to  When reporting observations, don't forget to tell us
which mode you were operating.

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

Also, check this article from September, 2002 QST:

An archive of past propagation bulletins is at . More good
information and tutorials on propagation are at

Instructions for starting or ending email distribution of ARRL
bulletins are at .

Sunspot numbers for August 10 through 16, 2023 were 83, 105, 61, 89,
85, 107, and 140, with a mean of 95.7  10.7 cm flux was 155.7,
152.8, 148.3, 150.4, 154, 158.1, and 160.1, with a mean of 154.2.
Estimated planetary A indices were 7, 5, 8, 5, 5, 4, and 8, with a
mean of 6. Middle latitude A index was 8, 6, 10, 7, 6, 7, and 10,
with a mean of 7.7.


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