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ARRL Propagation Bulletin ARLP032 (2021)

ARLP032 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 32  ARLP032
From Tad Cook, K7RA
Seattle, WA  August 6, 2021
To all radio amateurs 

ARLP032 Propagation de K7RA

During this reporting week (July 29 through August 4) solar activity
dropped into a sharp decline.
Sunspots were gone on July 28 through August 1, so average daily
sunspot number dropped from 33.1 in last week's bulletin to 6 this
Average daily solar flux went from 83 to 74.8.
Predicted solar flux is 74 and 73 on August 6 and 7, 75 on August 8
to 10, 74 on August 11 and 12, 75 on August 3 to 14, 76 on August 15
and 16, 75 and 74 on August 17 and 18, 72 on August 19 to 31, 74 on
September 1, and 75 on September 2 to 10.
Predicted planetary A index is 12, 8 and 8 on August 6 to 8, then 5,
10 and 8 on August 9 to 11, 5 on August 12 to 15, then 10, 8 and 8
on August 16 to 18, 5 on August 19 to 22, then 8, 12 and 8 on August
23 to 25, 5 on August 26 to 31, then 12 and 10 on September 1 and 2,
and 5 on September 3 to 11.
"Geomagnetic activity forecast for the period August 6 to 31, 2021
Geomagnetic field will be 
Quiet on August 12 and 13, 20 and 21, 23, 28 
Quiet to unsettled on August 7 to 9, 14, 19, 22, 25 to 27, 31 
Quiet to active on August 6, 11, 15 to 18, 29 and 30 
Unsettled to active August 10, 24 
Active to disturbed Nothing predicted 

- Parenthesis means lower probability of activity enhancement.
- Next Thursday, on August 12th, I will not compile a forecast of
the Earth's magnetic field activity, because I will climb the
highest mountains of my country again.  But without the convenience
of civilization as a computer.  F. K. Janda, OK1HH"
Jon Jones, N0JK wrote:
"There was a 2 Meter sporadic-E opening August 4.
Ron, WZ1V (FN31) reported to me that he worked KA9CFD (EN40), K0TPP
(EM48) and  W5LDA (EM15) around 2225z on FT8 via Es.  He said KA9CFD
was loud.
2 Meter Es is very rare in the month of August.
The last week of July there was a strong tropospheric opening on 2
Meters from northeast Kansas.  I worked as far as KE8FD (EN80) and
W3CP (EM74) on 2 Meter FT8.  I had a psk flag on 2 Meters from W3IP
(FM19) over 1,500 kilometers away.
The Perseids Meteor shower is building in intensity with people now
making morning MSK144 contacts on 2 Meters.  The peak is the night
of August 11 and morning August 12.
More information here:  "
Ken Brown, N4SO on Alabama's Gulf Coast reports:
"On July 30, the EISN sunspot number was 0, and July 31 just above
Based on EISN, Estimated International Sunspot Number and I was
still able to log VE3TEN, KA3JOE and W2DLL in CANADA, PA and NY,
nearly a straight line to the North East.
On July 31, I was still able to log K6FRC/B at 1454 UTC.  Weak but
readable 339 RST.
On August 1, at 0400 UTC, 11 PM local I had that long list starting
with N9TNY, W8EH, WA2SFT, WI4L, and K4JEE, in order EN51, EM79,
EM76, EM74, and EM78.  Straight line North and Northeast."
From multiple sources:
"What follows is the text from a News Release from the High Altitude
Observatory in Colorado regarding the revision of their Solar Cycle
25 Predictions.  The parts about Radio Propagation and the
progression of Solar Cycle 24 are my own.
News Release - A revised prediction from the NASA High Altitude
Observatory based at the University Of Colorado.  NASA
Heliophysicists have released a revised prediction for Solar Cycle
25.  The report generated by Ricky Egeland a Solar Physicist working
in the NASA Space Radiation Analysis Group now calls for the peak of
Solar Cycle 25 to top out at a value of 195 +/- 17 based upon the
new scale for calculating Smoothed Sunspot Number.  For reference
Solar Cycle 21 peaked at an SSN 233 (new scale) while Solar Cycle 23
peaked at an SSN of 180 (new scale).

If this prediction holds up Ham Radio will see Excellent Worldwide F
Layer Conditions on 10 Meters for several years around Solar Max.  6
Meters conditions should be good in the Equinox Periods before and
after Solar Max with consistent openings on Medium Haul Polar
Routes.  6 Meter routes traversing the equator should experience
consistent openings +/- 9 months from Solar Max."
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
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 July 29 through August 4, 2021 were 0, 0, 0, 0,
13, 15, and 14, with a mean of 6.  10.7 cm flux was 75.8, 75.5,
75.9, 74.9, 74.6, 75.9, and 70.8, with a mean of 74.8.  Estimated
planetary A indices were 8, 6, 6, 4, 17, 10, and 5, with a mean of
8.  Middle latitude A index was 12, 6, 6, 4, 13, 15, and 5, with a
mean of 8.7.


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