ARRL

ARRL Propagation Bulletin ARLP027 (2013)

SB PROP @ ARL $ARLP027
ARLP027 Propagation de K7RA

ZCZC AP27
QST de W1AW  
Propagation Forecast Bulletin 27  ARLP027
From Tad Cook, K7RA
Seattle, WA  July 5, 2013
To all radio amateurs 

SB PROP ARL ARLP027
ARLP027 Propagation de K7RA

This week solar activity fell and then rose again, with average
daily sunspot numbers down 23.6 points to 86.1.  Average daily solar
flux fell from 122 to 107.2.  The solar flux on Thursday, July 4
rose to 137.7, the highest since May 16, fifty days earlier.
 
There was an active geomagnetic day on Saturday, June 29 when
planetary A index was 51, high latitude college A index was 73, and
mid-latitude A index was 40.
 
The high geomagnetic activity actually occurred on Friday night on
the West Coast, with a planetary A index of 6 at 0300 UTC (Saturday
UTC time) and 7 at 0600 UTC.  My friend Diana Sorus has been asking
me when to go out to see aurora, and I've told her to go to a dark
place and look north when the K index is high.
 
I suggested watching http://www.swpc.noaa.gov/ftpdir/indices/DGD.txt
and the daily predictions at
http://www.swpc.noaa.gov/ftpmenu/forecasts/45DF.html and to hope for
clear skies.  The usual problem in the Puget Sound basin of the
Pacific Northwest is we have so many overcast days, the chances of
seeing aurora are limited.  You need just the right combination of
high K index (5 or 6 or more), dark skies, and clear weather.  Diana
wanted to be sure to catch the next one, so she subscribed to a
service from spaceweather.com which calls or texts her whenever the
K index reaches some threshold designated by her.
 
Last Friday evening she got that call, but unfortunately was too
tired from working that day to venture out of the city to watch for
aurora.  This is unfortunate, because aurora was visible that night
in many places, including areas far south of us (aurora is more
intense the further away you are from the equator).  Skies here have
been clear for days, and we had a heat wave over the weekend.  I
don't know when she will get that chance again.  Could be next week,
next month or next solar cycle.  I wasn't watching conditions
closely enough to go out and observe for myself.
 
As you can see at
http://www.swpc.noaa.gov/ftpdir/indices/oldindices/2013Q2DGD.txt,
http://www.swpc.noaa.gov/ftpdir/indices/oldindices/2013Q1DGD.txt,
http://www.swpc.noaa.gov/ftpdir/indices/oldindices/2012DGD.txt and
http://www.swpc.noaa.gov/ftpdir/indices/oldindices/2011DGD.txt the
right combination is rare.
 
Back on March 1, 2011 the numbers look high enough, but locally the
peak activity was during daylight.  March 11, 2011 also had a peak
at daylight, although the evening hours may have been good also, but
March in Seattle tends to be overcast.  I tried to find weather
records online that would tell me the sky conditions, clear or
overcast, but it seems I found everything but that.  I did find
visibility, which is typically 8-10 miles.  An alternative for us is
to hop on Interstate 90 and head east 100 miles over the Cascade
mountain range to Eastern Washington, where skies are often clear.
 
The latest prediction (Thursday, July 4) has solar flux relatively
high for the next few days, at 140 on July 5 and 6, 135 on July 7,
140 on July 8 to 10, then 135, 130 and 120 on July 11 to 13, 125 on
July 14 to 16, 130 on July 17 to 19, then 120 and 115 on July 20 and
21, and 110 on July 22 and 23.  The forecast shows solar flux
reaching a minimum of 100 on July 26 and 27, then another minimum at
95 on August 2, and another peak at 130 on August 13 to 14.
 
Predicted planetary A index is 20 on July 5, 15 on July 6, 8 on July
7, 5 on July 8 to 16, followed by 10 on July 17, 15 on July 18 to
20, 18 on July 21, and 5 on July 22 to 26.  The geomagnetic indices
then show active conditions for the following six days.
 
OK1HH tells us he predicts geomagnetic conditions as mostly quiet on
July 5, quiet to active July 6, quiet to unsettled, July 7, quiet
July 8 to 15, mostly quiet July 16 and 17, quiet to active July 18
and 19, active to disturbed July 20, quiet to active July 21, mostly
quiet July 22, quiet July 23 and 24, quiet to unsettled July 25, and
quiet to active July 26 and 27.
 
At the beginning of the new month, it is now time to look at our
3-month moving average of daily sunspot numbers.  The average for
the three months centered on May, 2013 (April 1 through June 30) was
106.4, the same as the 3 month average centered on April, 2013
(March 1 through May 31).  Actually the two averages were not
exactly the same, with the latest 3 months lower by .028.  The early
period had a sum of 9,792 divided by 92 days, and the latest total
was 9,683 divided by 91 days.  The daily sunspot number average for
June was just 80.2, a drop from 125.6 in May.
 
The progression of our moving 3 month average for the past year,
centered on June 2012 through May 2013 was 96.5, 91.9, 89.9, 81.2,
82.3, 74.4, 82.8, 73.6, 80.7, 85.2, 106.4 and 106.4.
 
Some radio amateurs have said that perhaps this will be a
double-peak solar cycle, like the last one.  We don't know what the
rest of the year will bring, but the most recent NASA prediction
said the peak of the current cycle would likely be in the summer of
2013, which is now.   Remember that exciting period of relatively
high activity (at least for this weak solar cycle) in fall 2011? Our
3-month moving averaged peaked in October and November 2011, at
118.8 and 118.6.  Now we get two months in a row with 3-month
averages higher than any period since the end of 2011, at 106.4 and
106.4.  I hope this isn't as high as it goes.
 
As we've noted during peaks of the previous solar cycles 22 and 23,
because the determination of the peak is actually seen using a
12-month moving average, we don't really know when the peak was
until well afterward, perhaps a couple of years out.  The long
moving average is used to determine the official peak because there
is so much day-to-day and month to month variation in sunspot
numbers.
 
An interesting inquiry arrived from Don Prahl, CP4DR/KV7Q:
 
"I am living in southwestern Bolivia (FG68) high in the Andes
Mountains with a station elevation at 4,000 meters (13,000 ft.) I
have a very modest station running 100 watts to a vertical on the
roof for HF and a roof mounted dipole for 6 meters.  The broad side
of the dipole is looking north.  When I am rag chewing I tell folks
I have a very modest station but a tower that is almost 2 1/2 miles
high!  While kidding about the elevation of my antenna above sea
level is fun, it makes me wonder if a station closer to the ionized
layer actually presents any advantage.

I have read a lot of articles regarding the advantages of tower
height above ground as it pertains to angle of radiation but I have
never found any information looking at it just a bit differently.
The question would be, with all things being equal (antenna, power
output, ionized layer altitude, etc.) would a transmitting signal at
13,000 feet above sea level achieve a longer single path hop than
the same station at sea level? If there is an advantage, it would be
interesting to see what the ratio of height above sea level to the
gain at the receiving end is.  Hey, it is tough to breath at this
altitude so I need any advantage I can get!
 
I know that Bolivia is a much needed prize on six meters so I am
patiently waiting for that perfect set of conditions so I can
confirm CP land to those who are looking.  As such, I am really
thinking about 50 MHZ.  when I pose this question to you."
 
Thanks, Don.  Sounds like a great location.  The only advantage I
can think of is that the horizon is more likely to be further away,
so lower angles of radiation should be practical.  I will cc this to
K9LA to see what he thinks.  If you are looking down on everything
to the north, it seems like it would be great for communicating with
North America on VHF.
 
As always, K9LA gave an excellent and instructive response:
 
"Go to http://k9la.us.  Click on the 'Basic Concepts' link on the
left.  Then select the article titled The M-Factor.
 
What you'll see is how the hop distance and the M-Factor (M-Factor =
MUF / critical frequency) change versus vertical distance to the
ionosphere.  This isn't exactly your situation - your situation is
with but one end at a different height.  But we can use my work to
see how much an effect this is.
 
The difference in hop distance and M-Factor is as follows.
 
If propagation is via a 5 degree elevation angle to the F2 region at
300 km
 
Normal hop = 2878 km, M-Factor = 3.25
 
2.5 miles closer hop = 2855 km, M-Factor = 3.26
 
If propagation is via a 5 degree elevation angle to the E region at
110 km
 
Normal hop = 1487 km, M-Factor = 4.94
 
2.5 miles closer hop = 1448 km, M-Factor = 5.01
 
The hop length decreases when you are closer to the ionosphere
because the wave encounters the ionosphere closer to you.  But the
M-Factor increases when you are closer because the angle of
incidence on the ionosphere is smaller.  The effect of being a bit
closer to the ionosphere is greatest for the E region.
 
In summary, the effect of being 2.5 miles closer is certainly there
- but it is a pretty small effect.   Whether it could be discerned
in the real world is questionable."
 
Thanks, Carl!
 
Jon Jones, N0JK wrote on June 28: "Caught a somewhat unusual opening
to the Pacific Northwest June 26 on 6 meters from Lawrence, Kansas
EM28.  I worked N7NW CN87 (Fox Island, Washington), W7EW CN84
(Salem, Oregon) and W7SX CN84 (Elmira, Oregon) around 0335 UTC.
N7NW was probably the loudest of the three."
 
"This is unusual due to the distance from EM28 to the CN80 grids.
It is about 2,500 km.  (about 1500 miles).  It is a tough distance
as it is between the maximum limit for one hop Es (2,300 km) and
shorter than the usual range for double hop Es at 3,600-4,400 km.
Thus the Pacific Northwest stations are rare on 6 meter Es here in
Eastern Kansas.  Stations further west like N0LL EM09 (North-Central
Kansas) and K0BJ DM99 (Northwest Kansas) work it much more
frequently as they are in the usual one Es hop zone.  There is a
discussion of this here:
 
http://www.uksmg.org/content/doughnut.htm "
 
Later the same day, Jon wrote: "Some aurora this evening, the first
I have worked since fall of 2011.  On 6 meters I heard WI9WI, AA9A,
KC0CF, WB0RMO/b, a EN26 station on SSB, and K9WKW via Aurora from
Lawrence, KS from 0030-0130 UTC June 29."
 
"I worked WA9LFO EN54 (who answered my CQ) on 50.098 MHz at 0107
UTC.  I was portable with 100 watts and a 2 element Yagi from a nice
hill top west of Lawrence overlooking the Kansas River valley to the
north."
 
"This aurora was not 'predicted.' It seemed to occur when the Bz
went way south the afternoon of the 28th."
 
And this week, six meter newcomer Howard Lester, N7SO of
Schuylerville, New York (FN33) wrote:
 
"HEY!  It was my first ever 6 meter opening.  I made a whole bunch of
contacts from 2330-0100 to as far west as Missouri, and as far south
as Florida.
 
On DX Watch at around 2310 Thursday night, July 3 I noticed that a
few contacts were being made on 6 meters, so I decided to listen.  A
newcomer to 6 with my loop antenna at 15 feet, I heard some signals
coming through, starting with a W4.  Since I have only the little
loop for an antenna, and not very high, I didn't expect much for
myself.  At first, my expectations were confirmed, but in a few
minutes I made contact with my first ever 'DX' on 6 with two fellows
in Knoxville, Tennessee, and got a good report from both.  Over the
course of the next two hours I worked twelve stations in nine states
on both phone and CW, as far west as Des Moines, Iowa, southeast to
Knoxville, and south to north Florida - all with good reports.
Granted, some or most of the stations I worked have more sizeable
antennas, though one was a mobile in northern Illinois, who I worked
on July 4 at 0115.  He was my final contact for the night.
 
There seemed to be no pattern, no shifting around of the available
propagation; it just 'opened up.' I could hear Southern stations
working up into Ontario and Quebec, and I didn't notice them working
anyone to their west.  Overall, I sure had a lot of fun."
 
And finally, regarding my report last week of my casual Field Day
operation as 1C class mobile, it probably didn't meet the
requirements for 1C class.  I was able to drive around the cemetery
dragging the counterpoise wires, but the screwdriver antenna hanging
out the rear passenger window seems a bit much, so it would probably
be classed as a portable operation.
 
For more information concerning radio propagation, see the ARRL
Technical Information Service 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.  More good
information and tutorials on propagation are at http://k9la.us/.
 
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 June 27 through July 3 were 71, 83, 67, 85,
102, 101, and 94, with a mean of 86.1.  10.7 cm flux was 99.5, 101,
100.2, 102.8, 107.8, 114.3, and 124.5, with a mean of 107.2.
Estimated planetary A indices were 8, 22, 51, 11, 8, 4, and 4, with
a mean of 15.4.  Estimated mid-latitude A indices were 8, 20, 40,
11, 10, 5, and 4, with a mean of 14.
NNNN
/EX