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ARRL Propagation Bulletin ARLP036 (2019)

ARLP036 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 36  ARLP036
From Tad Cook, K7RA
Seattle, WA  September 6, 2019
To all radio amateurs 

ARLP036 Propagation de K7RA

Old Solar Cycle 24 sunspots returned this week, but for only two
days (Sunday and Monday) with a sunspot number of 12. Average daily
solar flux increased from 66 reported in last week's Propagation
Forecast Bulletin ARLP035 to 67.4 this week.

Radiation from a coronal hole increased the average planetary A
index from 5.7 last week to 19.9 this week, with the level on
Saturday and Sunday at 38 and 45. In Fairbanks, Alaska's College A
index reached 59 and 86, and at one point on Sunday the K index was

The College K index (a component measured every 3 hours, and used to
calculate the daily A index) had not previously reached 8 since
twice in 2018, on August 26 and two weeks later on September 11.

Predicted solar flux is 68 on September 6-13, 67 on September 14-22,
68 on September 23 through October 6, then 67 on October 7-19 and 68
on October 20.

Predicted planetary A index is 10, 8 and 8 on September 6-8, 5 on
September 9-22, 8 on September 23, 5 on September 24-25, then 10,
35, 44, 24 and 8 on September 26-30, 5 on October 1-3, 8 on October
4-5, 5 on October 6-19 and 8 on October 20.

Geomagnetic activity forecast for the period September 06-October
02, 2019 from F.K. Janda, OK1HH.

"Geomagnetic field will be:
Quiet on: September 10-11, 15-16, 20 (-21)
Quiet to unsettled on: September 8, 13, 18-19, 22, (25)
Quiet to active on: September (9, 12, 14, 17,) 23-24, 30
Unsettled to active on: September (6-7, 26)
Active to disturbed: September (27-29)

"Solar wind will intensify on: September 6, 16-18, (24-27,) 28-30.
October 1-2

"- Parenthesis means lower probability of activity enhancement. 
 - The predictability of changes is lower at present."

Lance Collister, W7GJ of Frenchtown, Montana wrote:

"Even though ionospheric propagation (other than Es) seems a distant
memory for most of us in northern latitudes, low solar activity
means great conditions for 6m EME.

"And activity on 6m EME has been steadily increasing due to the
increased use of the very sensitive digital mode of JT65A and the
rapidly expanding 6m arrays and amplifiers around the world!

"If you are having trouble keeping track of all the recent activity
on 6m EME, you are not alone! This has been an amazing year for 6m
EME DXpeditions! I count 14 new DXCC being activated on 6m EME this
year. In addition to new DXCC such as ZL7DX and 9K2GS home stations
coming on the air this year, there already have been 6m EME
DXpeditions to V84SAA, T77C, CP1GJ, and CY9C! But be sure to get
things ready for even more to come! In the next few months, watch
for S79GJ, HB0/S59A, A35JT, VP6R, ZK3A, A21EME, 5H3EME, VP8DBL and

Peter Greene, N2LVI of Marlton, New Jersey noted that I mistakenly
called the solar flux measurements at 10.7 GHz, when I should have
said 10.7 cm and 2.8 GHz.

Peter sent us a resource for historical solar flux values:

He noted:

"On a monthly basis, the lowest average since 1947 was in May 1954
(65.36). The most recent low was July 2008 (65.67)."

Jim, WB6BET sent similar historical data.

K3WWP also offered data. But look at his website documenting his
long devotion to CW and QRP:

Jeff, N8II in West Virginia sent what he called a "brief, late

"I took part in the Kansas QSO party August 24-25. Propagation on
the 24th was definitely near rock bottom. Kansas is a good distance
from here for a single F2 hop about 1400-1500 miles to the western
border. Starting 2000Z signals weakened on 20M, by 2100Z activity
was quite low and when I returned at 2220Z the band was nearly dead,
but I still managed about 6-8 more QSOs, the last with extremely
weak signals. And 40 meter signals were also weak until about 2345Z
which is 15 minutes before my sunset. Despite similar SFI, Sunday
was much better with good conditions on 20M throughout the day and
40 was good from 1400-1530Z.

"The mobiles were all easy to hear and work on 20 and they were much
busier with more callers than Saturday. 15 appeared to be completely
closed to Kansas. I heard and worked KH6LC on 15 CW around 1700Z.

"Despite the poor conditions, thanks to good Kansas activity, I
managed to work all 105 counties, the last 19 minutes before the end
at 1941Z. I also worked all 56 of the active 1x1 special KSQP calls.
So, even at the cycle bottom, it is possible to have fun and do

Dr. Tamitha Skov, WX6SWW released a new video on September 5:

I will be giving a talk about my history in ham radio (I was
licensed at age 12, many years ago), propagation, (and they said I
can talk about anything else I want) at the Western Washington DX
Club in Seattle on Tuesday, September 10. See
for details.

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 web page 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

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 August 29 through September 4, 2019 were 0, 0,
0, 12, 12, 0, and 0, with a mean of 3.4. 10.7 cm flux was 65.9,
66.5, 66.4, 67.1, 68.8, 68.6, and 68.6, with a mean of 67.4.
Estimated planetary A indices were 3, 10, 38, 45, 21, 10, and 12,
with a mean of 19.9. Middle latitude A index was 4, 10, 29, 33, 19,
11, and 11, with a mean of 16.7.


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