Transcript DXU - K9LA

Propagation Considerations
Carl Luetzelschwab K9LA
DXU at W9DXCC 2014
DX’ing from the Black Hole
Carl Luetzelschwab K9LA
Carl was licensed as WN9AVT in October
1961. He selected K9LA in 1977 when the FCC
offered 1 x 2 call signs to Extra Class licensees.
Carl enjoys propagation, DXing, contesting (he
was the Editor of The National Contest Journal
from 2002-2007), antennas and vintage rigs.
He earned a BSEE and MSEE from Purdue
University, and retired in late 2013 as an RF
design engineer with Motorola (from 1974-1988)
and Raytheon (formerly Magnavox, from 19882013).
WN9AVT/WA9AVT
Carl is a card checker for both ARRL and CQ
awards, and is at the Top of the DXCC Honor
Roll,
DX’ing from the Black Hole
What We’ll Cover – Five Issues
• What do the numbers mean?
• Sf (solar flux), ssn (sunspot number), K and A
• When is the best time to work the DX station?
• When no one else is calling, of course
• Which way should I point my antenna?
• Short path? Long path? Skewed path? At the moon?
• What should I do when propagation is disturbed?
• Read a good book?
• What’s Cycle 24 Doing?
• And how about the CQ WW and ARRL DX contests?
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10.7 cm Solar Flux
• Measurement at 2800 MHz - objective
• From Planck’s Law, energy of one photon at
10.7 cm is 0.0000115 eV
• Need about 34 eV to ionize O (atomic oxygen) in
the F2 region
• Thus 10.7 cm solar flux has nothing to do with
ionization
• 10.7 cm solar flux is a proxy for the true
ionizing radiation, which is at wavelengths from
10 – 100 nm (EUV) for the F region
–Sunspots are also a proxy – and are a subjective
measurement
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10.7 cm Solar Flux
• This is why our
propagation
predictions are
statistical
(probabilities)
over a month’s
time frame
Correlation Between Daily MUF and Daily Solar Flux
3000 km MUF over Boulder, November 2011, 2100 UTC
40
2
R = 0.0475
daily MUF (MHz)
• Daily 10.7 cm
solar flux does
not correlate
well to daily
MUF
35
30
25
20
100
110
120
130
140
150
160
170
180
190
daily solar flux
Similar plot if use daily sunspot number
Similar plot if use EUV
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200
10.7 cm Solar Flux
• Reiterate: no short-term (daily) correlation to daily
MUF (two other parameters involved)
• Excellent long-term correlation to monthly median
MUF
• If 10.7 cm solar flux has been high for a long time,
higher bands should be better – and vice versa
• Short-term variation in 10.7 cm solar flux does not
necessarily indicate better or worse propagation on
the higher bands
–If solar flux goes up, MUF may go down
–If solar flux goes down, MUF may go up
Sunspot numbers behaves similarly
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K Index
• Variation of Earth’s
magnetic field in a 3hour period relative to a
quiet day
–Measured in nT
(nanoTeslas)
–Measurement of currents
flowing at E region
altitudes
–Values from 0 (quiet) to 9
(extremely disturbed)
• Plot of nT vs K is quasilogarithmic
each observatory has
its own range of nT
–nT on log scale, K on
linear scale
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K Index
F2 MUF at Jicamarca (12S/77W)
every hour for Aug 4-6, 2011
• When K is elevated
35
MHz or K-index
30
25
20
15
10
5
0
Augus t
4
Augus t 5
Augus t
6
F2 MUF at Eglin AFB (30N/87W)
every hour for Aug 4-6, 2011
40
35
MHz or K-index
–High latitude E region
ionization can increase
–Increased D region
absorption can occur in
and near auroral oval
–Usually the F region
ionization decreases at
mid and high latitudes
–The F region ionization
can increase at low
latitudes
30
25
20
15
10
5
0
Augus t
4
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Augus t 5
Augus t
6
A Index
• K index is a 3-hour index
• A index averages the eight 3hour K indices to arrive at a daily
index
–Have to convert each quasi-log K
index to a linear index (‘a’ index)
–Now can average the a indices to
get the daily A index
• A index values from 0 (quiet) to
400 (extremely disturbed)
• Plot of nT vs a is linear
–nT on linear scale, a on linear
scale
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What We Desire
• High bands and 6m F2
–High long-term 10.7 cm solar flux
–Low K and A indices
• Low bands
–Low long-term 10.7 cm solar flux
•But how much does it really matter since we DX on
160m in the dark ionosphere?
–Low K and A indices
• VHF aurora
–High K and A indices
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When Is the Best Time?
•HF propagation is due to refraction in the ionosphere
•The ionosphere varies considerably
•Amount of ionization varies by latitude
• Highest MUFs at low latitudes (around the equator)
• Lowest MUFs at high latitudes (polar regions)
• Most of us are in between those two extremes
•Amount of ionization varies over time
• Long-term – over a solar cycle
• Mid-term – throughout the seasons
• Short-term – throughout the day and even day-to-day
•And then there are anomalies!
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Best Time
• Ionosphere varies over a solar cycle
• Approximately 11 years from min to max
• Higher bands (15m/12m/10m) depend on
ionization (MUF) - best at solar max – where
we are now – during day
• Lower bands (160m/80m/40m) depend on
ionospheric absorption – best at solar min –
during night
• Mid bands (30m/20m/17m) hold up throughout
solar cycle
• If you can only put up one antenna for one band, go
for 20m
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Best Time
•High bands - needed ‘long-term’
solar flux or sunspot number for F2
openings
The Big Picture – sf, ssn, Ap
• 6-Meters: sf > 200 or ssn > 100
• 10-Meters: sf > 100 or ssn > 50
• 12-Meters: sf > 75 or ssn > 35
• 15-Meters: sf > 50 or ssn > 25
•All bands - Ap index less than 7
indicates quiet geomagnetic field
• Over the pole paths (high latitude)
are best
http://www.solen.info/solar/
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Best Time
• Ionosphere varies
throughout the seasons
• Composition of the
atmosphere changes
throughout the year
• More F2 region ionization
targets (atomic oxygen)
in the fall, winter and
spring months in the
northern hemisphere
generally results in
higher MUFs in these
months
Fall and winter are best for QSOs
in the northern hemisphere
DX’ing from the Black Hole
Best Time
• Ionosphere varies throughout the day
• The MUF maximizes during the day and minimizes during the night –
but not the same values on consecutive days
• Anomalies in the ionosphere
• For example, there are three areas in the world where the MUF
maximizes during the night
• Around Japan, off the northeast coast of North America and over the
Weddell Sea near Antarctica
• So how do you make sense of all this variability?
• On the lower bands, the best times are when the path is in darkness –
especially around sunrise/sunset times
• On the higher bands, the best times are when the path is mostly in
daylight – in other words, point your antenna towards the Sun
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Best Time
•For specific predictions, propagation prediction software
packages available
• For example, two free ones are
• VOACAP
• Voice of America’s version of IONCAP
• W6ELProp
• More user friendly than VOACAP
• Has a very useful mapping application that includes great
circle paths (and the terminator) so you can see how your
RF usually gets from Point A to Point B
•Tutorials for these two are available at http://k9la.us
• Includes download instructions, set up instructions and
interpretation of results
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Best Time
• If you don’t want to roll your own . . .
• Use the predictions by N6BV
• Over 240 locations worldwide
Predictions from any
pin to any other pin
• Over six phases of a solar cycle
• Summary predictions to seven continental areas (EU, FE, SA, AF, AS,
OC, NA) on 80m, 40m, 20m, 15m, 10m
• Detailed predictions to all forty CQ zones on 160m – 10m (including
30m, 17m and 12m)
• http://radio-ware.com/books/N6BV.html
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Which Way Should I Point Antenna?
•Purpose of an antenna is to put the most energy
• at the required azimuth angle (N, NE, E, etc)
• at the required elevation angle (10o, 20o, etc)
• with the required polarization (horizontal, vertical, something else?)
•The ionosphere dictates these three parameters
•Biggest misconception may be that the higher the antenna, the
lower the ‘radiation angle’ and thus the better the signal strength
• But the ionosphere determines the elevation angle that gets
from Point A to Point B, not the antenna
• At times a higher angle (lower antenna) is best
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Which Way - Azimuth
• An electromagnetic wave travels in a
straight line unless it is refracted,
reflected, or scattered
• Shortest distance between two points
on a globe is a great circle path
• This is short path - airliners generally
fly short great circle paths to use the
minimum amount of fuel (exceptions
due to storms, winds, etc)
ANTIPODE
• Other way around is long path
• Location on opposite side of Earth to
your location is called your antipode
• Short path and long path are equal –
approx 20,000 km (12,500 miles)
Most of the time short path is
best – sometimes long path
is better – at other times gray
line is best
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Which Way - Azimuth
• Most of the time a great circle path is dictated
• Skewed paths and scatter paths sometimes available
• Use W6ELProp mapping feature to see the great
circle paths (and the terminator)
• With respect to polarization, circular polarization is
predominant on the HF bands
• Horizontal or vertical equally good
• Only down 3 dB if the gains are the same
• My preference is horizontal antenna
• Vertical antenna picks up more man-made noise and is more
ground dependent
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Which Way - Azimuth
Example: W6 to EU on 75-Meter LP via gray line
• Generally occurs from
November thru March
• Around W6 sunrise
• Good signal strengths
without high power
levels and without big
antennas
• Example shown is
classical “gray line”
propagation
Good example of the mapping
application in W6ELProp
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Which Way - Azimuth
Example: 10-Meter LP for North America
factor
solar activity
month
sunrise end of path
sunset end of path
headings
condition
smoothed 10.7 cm solar flux > about 120
smoothed sunspot number > about 70
mostly March thru September
first F2 hop in daylight
not later than about 4 hours after sunset
in the morning: southeast through south
in the evening: south through southwest
For W9, morning long
path to SE Asia is most
productive
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Which Way - Elevation
EU
JA
AF
SE Asia
OC
SA
USA
30
Elevation angles (N6BV data) required
on 10-Meters for Indianapolis
25
percetn of the time
20
15
10
5
0
1
2
3
4
5
6
7
8
9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31
elevation angle, degrees
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Which Way - Elevation
Antenna elevation patterns
5-el a t 25 ft
5-el a t 50 ft
5-el a t 100 ft
20
perc etn of the time or g ain in
dB i
15
10
5
0
1
2
3
4
5
6
7
8
9
10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32
elev atio n an g le, d eg rees
5-element HyGain monobander over average ground
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Which Way - Elevation
Superimpose required elevation angles on antenna patterns
all elevation angles
5-el at 25 ft
5-el at 50 ft
5-el at 100 ft
percetn of the time or gain in dBi
20.0
• Data available on
other bands
• To cover all the
elevation angles,
probably need
stack of antennas
15.0
10.0
5.0
0.0
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32
• Tough to achieve
low angle
radiation on low
bands
elevation angle, degrees
• At 25 ft (red) – doesn’t cover the low angles (< 10o) very well
• At 100 ft (purple) – covers the low angles, but has two nulls at 10o and 20o
• At 50 ft (blue) – probably the best height overall for a single Yagi – 1.5 λ
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Disturbances to Propagation
• Review summary conditions at http://www.swpc.noaa.gov/
• G = Geomagnetic storm - disturbance in the Earth’s magnetic field caused by
gusts in the solar wind that blow by Earth (CMEs and coronal holes)
• S = Solar radiation storm – disturbance in the polar cap due to increased levels of
energetic protons (from big solar flares)
• R = Radio blackout – disturbance on the daylight side of Earth due to increased
electromagnetic radiation at X-ray wavelengths (from big solar flares)
• Each is on a scale of 1 (minor) to 5 (extreme)
• More details at http://www.swpc.noaa.gov/NOAAscales/
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Disturbances
Disturbances to Propagation
– A Visual Picture
1a) Geomagnetic
storm – decreased F2
region MUFs at high
and mid latitudes both
day and night
3) Radio blackout –
increased absorption
on daylight side of
Earth due to
extremely short
wavelength
electromagnetic
radiation from a big
solar flare
X
2) Solar radiation
storm (a.k.a. PCA) –
increased D region
absorption in the
polar cap due to
energetic protons
from a big solar
flare
North magnetic pole
Solar flares and CMEs not
necessarily concurrent
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1b) Geomagnetic
storm – increased
auroral ionization
causing increased
absorption and
horizontal refraction
(skewed path)
Disturbances - Mitigation
•Geomagnetic storm – effect can last up to a week
• Check for auroral propagation at VHF
• Check for skewed paths on 160m
• Move down in frequency on HF paths thru mid and high latitudes
• Look for enhanced low latitude paths (e.g., southern USA to VK/ZL)
•Solar radiation storm – effect can last up to several days
• For paths over the poles, try long path if the short path is degraded and vice
versa (since the effect is not necessarily similar in the north and south polar
caps)
•Radio blackout – effect can last up to several hours
• Move to the higher frequencies
• Use paths that are in darkness
DX’ing from the Black Hole
Cycle 24
Cycle 24 in terms of 10. 7 cm solar flux
180
latest monthly
August 2014
10.7 cm Solar Flux
160
latest smoothed
February 2014
140
120
100
80
60
Jan
Jul
Jan
2009
Jul
2010
Jan
Jul
2011
Jan
Jul
2012
Jan
Jul
Jan
2013
Jul
2014
Jan
Jul
Jan
2015
K9LA - Mar 2014
•We’re in the second peak
•Higher bands should be good this fall/winter
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Summary
• Understand the numbers
• Generally we desire high solar flux, and low K and A
• When is the best time to work the DX station?
• Lower bands – solar min, night, special attention around
sunrise/sunset
• Higher bands – solar max, path mostly in daylight (can tolerate some
darkness)
• Use propagation predictions to pin down more specific times
DX’ing from the Black Hole
Summary - continued
• Which way should I point my antenna?
• Use propagation predictions and mapping feature to identify short
path, long path and gray line path
• Short great circle path best most of the time
• Don’t ignore elevation angles
• Polarization is an issue on 160-meters – vertical is best for mid
latitude and high latitude stations in the northern hemisphere
• What should I do when propagation is disturbed?
• Try the suggestions on the “disturbances” slide – no guarantees!
• Get on the higher bands now!
• Second peak of Cycle 24 won’t last forever
• Read, read, read to understand more
DX’ing from the Black Hole
References for Your Library
Books
Robert Brown NM7M (SK) “The Little Pistol’s Guide to HF
Propagation” - available at http://k9la.us – moderate
reading
The NEW Short Wave Propagation Handbook (W3ASKN4XX-K6GKU, CQ, 1995) – light reading
Radio Amateurs Guide to the Ionosphere (Leo McNamara,
Krieger Publishing, 1994) – moderate reading
Ionospheric Radio (Kenneth Davies, Peter Peregrinus Ltd,
1990) – heavy reading
Visit http://k9la.us – timely topics, basic concepts, tutorials,
general, 160m, HF, VHF, contesting and webinars on
propagation
DX’ing from the Black Hole