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ARRL Propagation Bulletin ARLP021 (2005)

ARLP021 Propagation de K7RA

QST de W1AW  
Propagation Forecast Bulletin 21  ARLP021
From Tad Cook, K7RA
Seattle, WA  May 19, 2005
To all radio amateurs 

ARLP021 Propagation de K7RA

There was so much remarkable solar and geomagnetic activity over the
last weekend that we put out a special bulletin Sunday night. If you
missed it, find it at, which has an
archive of past propagation bulletins.

The last bulletin reported a TV DXer in Florida who copied a channel
2 television broadcaster in Iowa. Bill Smith, W0WOI of Jefferson,
Iowa wrote to say that the TV DX was probably due to sporadic-E
skip. This is propagation through the E layer of the ionosphere
(lower than the F layers) that occurs in May, June and early July,
and is responsible for a many 6 and 10 meter openings, even when
there aren't many sunspots.

Bill said that KGAN "is one of the more frequently reported stations
nationwide due to its geographical location and channel 2 frequency,
just above 6 meters." By the way, Bill is the former editor of "The
World Above 50 MHz," the monthly column devoted to VHF in QST.

Ray Bass, W7YKN in Sparks, Nevada reports that last Friday he was
working W7QCY in Portland, Oregon on 40 meters, and around 9:40 AM
local time signals started to fade. A few minutes later, the band
was completely dead, no doubt due to the effects of the coronal mass

Dave Greer, N4KZ in Frankfort, Kentucky wrote that Tuesday, May 17
was a very interesting day for 6 meter fans. He worked stations all
over South and Central America as well as the Caribbean (LU, CX, TI,
VP5, ZF, HK) from late afternoon into evening. He said there were
many strong signals, but for some stations the conditions weren't
reciprocal. He heard HK3JRL in Bogota call CQ repeatedly with no
answer to responses. He heard a number of YV and KP4 stations that
he could not work.

Reviewing numbers from the past week, solar flux and sunspot numbers
were lower than the week before, and of course the big excitement
was May 15 when the planetary A index reached 105. For the next week
expect low solar flux and sunspot activity. Sunspot 759, the source
of all the excitement, is passing off the solar disk.  Geomagnetic
conditions should be unsettled for Thursday and Friday, May 19 and
20, but expect quiet conditions after that. Recurring coronal holes
could produce active geomagnetic conditions around May 27 or 28.

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

For more information concerning radio propagation and an explanation
of the numbers used in this bulletin see the ARRL Technical
Information Service propagation page at, An archive of past
bulletins is found at,

Sunspot numbers for May 12 through 18 were 110, 100, 91, 69, 70, 45
and 46 with a mean of 75.9. 10.7 cm flux was 117.4, 125.9, 99.5,
103, 99.1, 90 and 83.8, with a mean of 102.7. Estimated planetary A
indices were 17, 27, 8, 105, 33, 19 and 13 with a mean of 31.7.
Estimated mid-latitude A indices were 13, 21, 4, 44, 18, 10 and 6,
with a mean of 16.6.


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