ARRL

ARRL Propagation Bulletin ARLP041 (2011)

SB PROP @ ARL $ARLP041
ARLP041 Propagation de K7RA

ZCZC AP41
QST de W1AW  
Propagation Forecast Bulletin 41  ARLP041
From Tad Cook, K7RA
Seattle, WA  October 14, 2011
To all radio amateurs 

SB PROP ARL ARLP041
ARLP041 Propagation de K7RA

Robust solar activity continues.  Check http://www.spaceweather.com
for daily images of the Sun, and you'll see it is full of spots. You
can also use the archive feature to view the position of sunspots
for previous days.

The average daily sunspot number for the week (95.4) was about the
same as last week (96.7) and the week before (96.1). The number
hasn't stayed steady though, with daily variation as low as 82 and
as high as 126 over the past two weeks.  You can check
http://www.swpc.noaa.gov/ftpmenu/forecasts/SRS.html for daily
updates showing which numbered groups appeared and faded away, along
with the relative area covered by each one.

The latest forecast from USAF/NOAA has solar flux at 135 on October
14-15, 130 on October 16-20, 125 on October 21 through November 2,
120 on November 3-5, and 125 on November 6-8.  The predicted
planetary A index is 5 on October 14, 8 on October 15-17, 5 on
October 18-27, 8 on October 28-30 and 5 on October 31 through
November 2.

Geophysical Institute Prague predicts quiet conditions on October
14, quiet to unsettled October 15, unsettled October 16, quiet to
unsettled October 17, and quiet October 18-20.

Lots of 10 meter activity lately, and Jeff Hartley, N8II of
Shepherdstown West Virginia sent this last week:

"Today, Oct 7th, the SFI was only 125 and 10M was wide open to EU at
1220Z (65 minutes after sunrise) with a very large amount of
activity. As we move into October, a bit lower SFI will produce
openings equivalent to those around the equinox 2 weeks ago with
higher MUFs. I started off the day breaking a EU pile up calling
7Z1TT in Saudi Arabia who was S9. I called one G running a vertical
and 100W who was S9 and two stations called me when signing. Then I
QSY'd up to 28530 kHz where there was still plenty of activity and
ran off about 10 QSOs before having to QRT. 10 was wide open to the
Moscow area and Great Britain which has been left out of many recent
openings; M0RAD was S9+25 dB. XU7SSB (Cambodia) was worked on 15 CW
S7 around 1300Z.

"T32C has been good strength to loud on all bands in the past week
and I've logged them on every HF band except 40M including both
modes on 15, 12, and 10M. 10M is routinely open to the Rockies and
west coast an hour or more after sunset and I was lucky enough to
have VK4FAXA running 10W call in from McClay Island, IOTA OC-137, on
10M last night. 10M conditions have been great except over the pole
from here, not that many JA/Asia openings."

Michael Gutman, K2CHM of Mashpee, Massachusetts writes, "10 meter
propagation is certainly feeling a lot like 1958.  I worked T32C on
10/9 at 7:25 PM on 28.485 MHz and he was 59.  It is impressive to me
as I run only 100 watts to a dipole in the attic here at sea level
on Cape Cod."

Mark Lunday, WD4ELG of Greensboro, North Carolina wrote on October
11, "Nothing gets the blood moving like a 10 meter opening at
sunrise! BY, 4K, ZD7, VU, 4S, and of course tons of EU stations, all
at 0800 local, and all audible on wire antennas.  Feels almost like
2001 all over again!

"In fact, 10 and 12 have been spectacular this week. I am rapidly
closing in on 9BDXCC using only LoTW...only 25 more to go on 12 and
10, then that leaves just 160 for the final jewel in the crown."

You can feel Mark's excitement! Check his blog at
http://wd4elg.blogspot.com/.

We also receive 6 meter reports. Anibal Dos Ramos, HK3R of Bogota,
Colombia says that on Sunday, October 9 he made his longest distance
6 meter contact yet. It was 2318 UTC when he contacted KH7Y on both
SSB and CW, and he heard KH7Y for about 30 minutes with S9 signals.
He estimates the distance was 8,897 km (5,528 miles) and he heard no
other Pacific stations.

There is much more on 6 meters and the recent meteor showers.
Perhaps we can report on that next week.

Roger Harrison, VK2ZRH sent an interesting email about propagation
of VHF signals from Dubai in the Middle East to the Far East. He
wrote:

"Over September 12-16, United Arab Emirates TV signals from Dubai on
48.25 - 53.75 MHz, were being copied in Shenzhen in south-east
China, Hong Kong and the Philippines, which are all in the UTC+8
time zone; Dubai is UTC+4. Dan VR2HF is the HK contact, while George
DU1GM is located 80 km south of Manila.

"The 48.25 MHz video signal typically reached S9+20 dB on peaks.
The 53.75 MHz sound channel was received for short periods when the
MUF peaked.

"Optimum reception time was around 1200-1300 UTC, although sometimes
signals were received in Hong Kong as early as 1130 UTC (1930 HK
local time).

"The propagation path ranges from about 5900 km to 7200 km and is
generally in daylight in mid-September. As this is the equinoctial
season, when the occurrence of sporadic E is a minimum, I thought
the propagation was most likely to be F2, requiring two hops of
about 3000 km each to Shenzhen/Hong Kong, and about 3600 km to DU1

"Dubai is located about 18 degrees N geomagnetic latitude, while
Shenzhen and Hong Kong are at about 11-12 degrees N geomagnetic
latitude. Manila is directly beneath the geomagnetic equator.

"The propagation path is largely beneath the northern Equatorial
Ionospheric Anomaly (also known as the Appleton anomaly) in the F2
region, which lies generally between 10 and 20 degrees geomagnetic
latitude north (another forms south of the geomagnetic equator). It
is the region of high electron density that forms late morning local
time, builds during the day and can last 6-7 hours into early
evening.

"For the Dubai to Shenzhen/Hong Kong path, the first F2 reflection
point would be 1500 km east of Dubai, near the northern extent of
the EIA, and in the UTC+5 time zone. The second F2 reflection point
would be about 4500 km east of Dubai, in the UTC+7 time zone and
near the middle of the EIA. To support 48 MHz propagation, foF2 at
each F2 reflection would need to be above 14.5 MHz as a 3000 km F2
skip has an M-factor of about 3.3.

"The only vertical incidence ionosonde with available online data
that I could locate in the EIA zone is at Guangzhou, about 100 km
northwest of Shenzhen, and 140 km northwest of Hong Kong. Although
at the propagation path's eastern end, the growth of the EIA
"follows the Sun" westward and the Guangzhou foF2 values provide a
good guide as to how the EIA develops during the day, from which we
can infer likely foF2 values west along the propagation path. NOAA's
Space Weather Prediction Center lists the Guangzhou ionosonde's
parameters here:
http://www.swpc.noaa.gov/ftpdir/lists/iono_month/201109_Guangzhou_iono.txt.

"For September 13, foF2 was above 16 MHz from 0500 to 1100 UTC,
which implies that the highest electron density of the EIA covered a
longitudinal extent of 6 hours. The 1st F2 reflection point will
determine when the path opens as the 2nd reflection point will be
well covered by the EIA. As the openings commenced around 1130-1200
UTC, the foF2 at the 1st reflection point must have reached 14.5 MHz
at 0830-0900 UTC, which is 3.5 hrs after foF2 hit 16 MHz at
Guangzhou. The discrepancy can be put down to the fact the 1st
reflection point is closer to the northern edge of the EIA, where
the electron density would take more time to accumulate to the high
values found near the middle of the EIA.

"Undoubtedly, the propagation experienced was supported by 2-hop F2
skip east-west along the EIA.

"The Dubai-DU1GM path is reported to experience longer durations and
higher signal strengths than the Dubai-Shenzhen/HK path. Each skip
is about 3600 km, just shorter than the maximum F2 skip of about
4000 km. For F2 skips of this length, the M-factor is about 4, so
foF2 only needs to reach 12 MHz to support 48 MHz propagation, and
the EIA achieves this earlier and sustains it longer.

"For the record, the 10.7 cm flux over September 12-16 was 124, 129,
143, 141, 143, and the A index was 17, 11, 5, 4, 2 (NOAA weekly
figures)."

If you would like to make a comment or have a tip for our readers,
email the author at, k7ra@arrl.net.

For more information concerning radio propagation, see the ARRL
Technical Information Service web page at
http://arrl.org/propagation-of-rf-signals. For an explanation of the
numbers used in this bulletin, see
http://arrl.org/the-sun-the-earth-the-ionosphere. An archive of past
propagation bulletins is at
http://arrl.org/w1aw-bulletins-archive-propagation. Find more good
information and tutorials on propagation at
http://myplace.frontier.com/~k9la/.

Monthly propagation charts between four USA regions and twelve
overseas locations are at http://arrl.org/propagation.

Instructions for starting or ending email distribution of ARRL
bulletins are at http://arrl.org/bulletins.

Sunspot numbers for October 6 through 12 were 99, 88, 61, 71, 87,
113, and 149, with a mean of 95.4. 10.7 cm flux was 123.9, 122,
118.4, 121, 126.4, 130.1, and 134.1, with a mean of 125.1. Estimated
planetary A indices were 7, 7, 7, 13, 3, 4, and 6, with a mean of
6.7. Estimated mid-latitude A indices were 6, 4, 5, 8, 2, 3, and 4
with a mean of 4.6.
NNNN
/EX