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Propagation Prediction Programs:
Their Development and Use
Carl Luetzelschwab K9LA
[email protected]://mysite.verizon.net/k9la
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What Were Going to Cover
How the ionosphere forms Measuring the ionosphere
Solar-ionosphere correlationVariability of the ionosphere Sample prediction
Understanding prediction outputsThis presentation will be on the PVRC website
visit http://www.pvrc.org/index.html
click on the PVRC Webinars link at the top
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How the Ionosphere Forms
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The Atmosphere Composition of the atmosphere
78.1% nitrogen, 20.9% oxygen, 1% other gases
Species that are important in the ionosphere
Maximum wavelength is longest wavelength of radiation thatcan cause ionization Related to ionization potential through Plancks Constant
10.7 cm = 107,000,000 nm 10.7 cm solar flux doesnt ionize anything It is a proxy (substitute) for the true ionizing radiation
The sunspot number is also a proxy Visible light = 400 to 700 nm
ionization potential maximum wavelength
O (atomic oxygen) 13.61 eV 91.1 nm
O2 (molecular oxygen) 12.08 eV 102.7 nm
N2 (molecular nitrogen) 15.58 eV 79.6 nm
NO (nitric oxide) 9.25 eV 134 nm
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True Ionizing Radiation
As radiation progresses down through the atmosphere,it is absorbed by the aforementioned species in theprocess of ionization
Energy reduced as it proceeds lower Need higher energy radiation (shorter wavelengths) to getlower
True ionizing radiation can be summarized as follows .1 to 1 nm and 121.5 nm for the D region
121.5 nm (Lyman- hydrogen spectral line) is the result of aminimum in the absorption coefficient of O2 and N2
It goes through the higher altitudes easily, and ionizes NO at loweraltitudes to give us daytime absorption
1 to 10 nm for the E region 10 to 100 nm for the F2 region Sunspots and 10.7 cm solar flux are
proxies for the true ionizing radiation
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Measuring the Ionosphere
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Introduction to Ionosondes
To make predictions, you need a model of theionosphere
Model developed from ionosonde data
Most ionosondes are equivalent to swept-frequencyradars that look straight up Co-located transmitter and receiver Also referred to as vertical ionosondes or vertically-incident
ionosondes
There are also oblique ionosondes Transmitter and receiver separated Evaluate a specific path
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What Does an Ionosonde Measure?
It measures the time for awave to go up, to be turnedaround, and to come backdown
Thus the true measurement istime, not height
This translates to virtual heightassuming the speed of lightand mirror-like reflection
The real wave does not get ashigh as the virtual height
An ionosonde measures time of flight,not altitude, at each frequency
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Sample Ionogram Red is ordinary wave, green
is extraordinary wave
Critical frequencies arehighest frequencies that arereturned to Earth from eachregion at vertical incidence
Electron density profile isderived from the ordinarywave data (along with acouple assumptions aboutregion thickness) Electron density anywhere
in the ionosphere is
equivalent to a plasmafrequency through theequation fp (Hz) = 9 x N
1/2
with N in electrons/m3 E region and F2 region have maximums in electron density F1 region is inflection point in electron density D region not measured Nighttime data only consists of F2 region and sporadic E due
to TX ERP and RX sensitivity (limit is ~1.8 MHz)
foE
foF1
foF2fxF2
electron density profile
daytime data
http://digisonde.haystack.edu
Note that we dont seelayers with gaps in between
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Characterizing the Ionosphere
Ionosphere is characterized in terms of criticalfrequencies (foE, foF1, foF2) and heights ofmaximum electron densities (hmE, hmF2) Easier to use than electron densities
Allows us to calculate propagation over obliquepaths MUF(2000)E = foE x M-Factor for E region
MUF(3000)F2 = foF2 x M-Factor for F2 region Rule of thumb: E region M-factor ~ 5, F2 region M-factor ~ 3
for more on the M-Factor, visit http://mysite.verizon.net/k9la/The_M-Factor.pdf
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SolarIonosphere Correlation
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Whats the Correlation?
Many years of solar data andworldwide ionosonde datacollected
The task of the propagationprediction developers was todetermine the correlation betweensolar data and ionosonde data
It would have been nice to find a
correlation between what theionosphere was doing on a givenday and what the Sun was doingon the same day
solar data
ionosonde data
???
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But That Didnt Happen
August 2009
August 2009 Zero sunspots Constant 10.7 cm flux
No correlation between daily values Low of 11.6 MHz on August 14 High of 21.5 MHz on August 16
Indicates there are other factors indetermining the ultimate ionization
Comment about CQ WW Phone 2007, 2008
MUF(3000)F2 over Wallops Island (VA) Ionosonde at 1700 UTC
0
5
10
15
20
25
1 3 5 7 9 11 1 3 15 1 7 1 9 21 2 3 25 2 7 2 9 31
day of August 2009
M
Hz
http://www.solen.info/solar/
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So Now What?
Not too good - the developerswere forced to come up witha statistical model over amonths time frame
Good smoothed solar flux(or smoothed sunspotnumber) and monthlymedian parameters
R2 = .0615
R2 = .8637
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How Do You Determine theMonthly Median?
day foF2
1 5.4
2 4.3
3 4.8
4 4.6
5 4.7
6 4.6
7 4.8
8 4.4
9 4.4
10 0
11 4.212 4.9
13 4.2
14 4.6
15 4.5
16 4.9
17 0
18 4.4
19 5.2
20 4.8
21 4.922 4.9
23 4.8
24 4.7
25 4.4
26 4.4
27 4.3
28 4.8
29 4.9
30 4.9
31 4.6
day foF2
11 4.2
13 4.2
2 4.3
27 4.3
8 4.4
9 4.4
18 4.4
25 4.4
26 4.4
15 4.5
4 4.6
6 4.6
14 4.6
31 4.6
5 4.7
24 4.7
3 4.8
7 4.8
20 4.8
23 4.8
28 4.8
12 4.9
16 4.9
21 4.9
22 4.9
29 4.9
30 4.9
19 5.2
1 5.4
raw data
put foF2 inascending order
median implies50%
half of thevaluesbelowmedian
half of thevaluesabovemedian
median
Variation aboutthe median
follows a Chi-squareddistribution, thusprobabilities canbe calculated(more on this
later)
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Correlation Between SF and SSN
Smoothed solar flux12 = 63.75 + 0.728 R12 + 0.00089 (R12)
2
Smoothed sunspot numberR12= (93918.4 + 1117.3 12)
1/2 406.37
Using these equations to convert betweendaily solar flux and daily sunspot numberresults in a lot of uncertainty
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Variability of the Ionosphere
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What Causes this Variability?
Rishbeth and Mendillo, Journal of Atmospheric and Solar-TerrestrialPhysics, Vol 63, 2001, pp 1661-1680 Looked at 34 years of foF2 data Used data from 13 ionosondes Day-to-day daytime variability (std dev/monthly mean) = 20%
Solar ionizing radiation contributed about 3% Solar wind, geomagnetic field activity, electrodynamics about 13% Neutral atmosphere about 15% [20%]2 = [3%]2 + [13%]2 + [15%]2
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Is the Ionosphere In Step?
3000 km MUFover Millstone Hilland WallopsIsland
Separated by 653km = 408 miles
Several periodsshow up whenthe ionospherewas goingopposite ways
Worldwideionosphere notnecessarily instep
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We Dont Have Daily Predictions
Day-to-day variability just too great We have a good understanding of the solar influence Were beginning to better understand the geomagnetic field
influence Its a bit more than just low K = good and high K = bad We are lacking a good understanding of how events in the
lower atmosphere couple up to the ionosphere This is a major reason why prediction programs dont cover 160m
(along with the effect of the Earths magnetic field through the
electron-gyro frequency) 160m RF doesnt get as high into the ionosphere as the higher
frequencies
Doesnt help that ionosondes dont measure the lower ionosphere especially at night when we chase DX on the low bands
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Summary So Far
Our propagation prediction programs are based on the correlationbetween a smoothed solar index and monthly median ionosphericparameters Monthly median parameters can be represented in different ways
Database of numerical coefficients Equations International Reference Ionosphere
Our predictions programs are pretty accurate when the geomagneticfield is quiet
Real-time MUF maps seen on the web are kind of a misnomer If they use a smoothed solar index, then theyre monthly median MUFs If they use todays solar flux or todays sunspot number (maybe even
with todays A index), I dont know what they are!
Now its time to run a sample prediction
We dont have daily predictions
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Sample Prediction
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K9LA to ZF
Latitudes / longitudes K9LA = 41.0N / 85.0W ZF = 19.5N / 80.5W
October 2004 Smoothed sunspot number ~ 35 (smoothed solar flux ~ 91)
Are we ever going to see that again? Antennas
Small Yagis on both ends = 12 dBi gain
Power 1000 Watts on both ends
Bands and Path 20m, 17m, 15m on the Short Path Well use VOACAP
When you download VOACAP (comes with ICEPAC and REC533),read the Technical Manual and Users Manual lots of good info
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VOACAP Input Parameters
Method Controls the type of program analysis and the predictions performed
Recommend using Method 30 (Short\Long Smoothing) most of the time
Methods 1 and 25 helpful for analysis of the ionosphere
Coefficients CCIR (International Radio Consultative Committee) Shortcomings over oceans and in southern hemisphere Most validated
URSI (International Union of Radio Scientists) Rush, et al, used aeronomic theory to fill in the gaps
Groups Month.Day
10.00 means centered on the middle of October 10.05 means centered on the 5th of October
Defaults to URSI coefficients
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VOACAP Input Parameters
System Noise default is residential
Min Angle 1 degree (emulate obstructions to radiation)
Req Rel default is 90% Req SNR 48 dB in 1 Hz (13 dB in 3 KHz: 90% intelligibility)
Multi Tol default is 3 dB
Multi Del default is .1 milliseconds
Fprob Multipliers to increase or reduce MUF
Default is 1.00 for foE, foF1, foF2 and 0.00 for foEs
For more details on setting up and running VOACAP, either visithttp://lipas.uwasa.fi/~jpe/voacap/ by Jari OH6BG (lots of good info) orhttp://mysite.verizon.net/k9la/Downloading_and_Using_VOACAP.PDF
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Prediction Printout13.0 20.9 14.1 18.1 21.2 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 FREQ
1F2 1F2 1F2 1F2 - - - - - - - - MODE
10.0 4.7 5.5 10.0 - - - - - - - - TANGLE
8.6 8.4 8.4 8.6 - - - - - - - - DELAY
347 222 240 347 - - - - - - - - V HITE
0.50 0.99 0.83 0.46 - - - - - - - - MUFday
123 112 113 124 - - - - - - - - LOSS
28 36 37 27 - - - - - - - - DBU-93 -82 -83 -94 - - - - - - - - S DBW
-168 -163 -166 -168 - - - - - - - - N DBW
75 80 83 74 - - - - - - - - SNR
-27 -32 -35 -26 - - - - - - - - RPWRG
0.90 1.00 1.00 0.89 - - - - - - - - REL
0.00 0.00 0.00 0.00 - - - - - - - - MPROB
1.00 1.00 1.00 1.00 - - - - - - - - S PRB
25.0 8.4 12.5 25.0 - - - - - - - - SIG LW
13.1 4.9 5.3 14.0 - - - - - - - - SIG UP
26.8 12.6 15.7 26.8 - - - - - - - - SNR LW
14.3 7.2 7.8 15.2 - - - - - - - - SNR UP
12.0 12.0 12.0 12.0 - - - - - - - - TGAIN
12.0 12.0 12.0 12.0 - - - - - - - - RGAIN
75 80 83 74 - - - - - - - - SNRxx
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Understanding Prediction Outputs
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Focus on 15m at 1300 UTC13.0 20.9 14.1 18.1 21.2 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 FREQ
1F2 1F2 1F2 1F2 - - - - - - - - MODE
10.0 4.7 5.5 10.0 - - - - - - - - TANGLE
8.6 8.4 8.4 8.6 - - - - - - - - DELAY
347 222 240 347 - - - - - - - - V HITE
0.50 0.99 0.83 0.46 - - - - - - - - MUFday
123 112 113 124 - - - - - - - - LOSS
28 36 37 27 - - - - - - - - DBU-93 -82 -83 -94 - - - - - - - - S DBW
-168 -163 -166 -168 - - - - - - - - N DBW
75 80 83 74 - - - - - - - - SNR
-27 -32 -35 -26 - - - - - - - - RPWRG
0.90 1.00 1.00 0.89 - - - - - - - - REL
0.00 0.00 0.00 0.00 - - - - - - - - MPROB
1.00 1.00 1.00 1.00 - - - - - - - - S PRB
25.0 8.4 12.5 25.0 - - - - - - - - SIG LW
13.1 4.9 5.3 14.0 - - - - - - - - SIG UP
26.8 12.6 15.7 26.8 - - - - - - - - SNR LW
14.3 7.2 7.8 15.2 - - - - - - - - SNR UP
12.0 12.0 12.0 12.0 - - - - - - - - TGAIN
12.0 12.0 12.0 12.0 - - - - - - - - RGAIN
75 80 83 74 - - - - - - - - SNRxx
monthlymedianMUF
time
MUFdayfor 15m
signalpower
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15m Openings at 1300 UTC
20.9 MHz (monthlymedian) Enough ionization on
half the days of themonth
21.2 MHz
Enough ionization on.46 x 31 = 14 days ofthe month
14 MHz and below Enough ionization every
day of the month
24.9 MHz
Enough ionization on 1day of the month
28.3 MHz Not enough ionization
on any dayWe cant predict which days are the good days
MUF Plot
5
10
15
20
25
30
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
MUFday(multiply by 31 to get the number of days in the month)
MH
z
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15m Signal Power
-94 dBW (monthly median) = -64 dBm Assume
S9 = -73 dBm (50 microvolts into 50) one S-unit = 5 dB
typical of receivers Ive measured
except below S3 or so its only a couple dB per S-unit -64 dBm = 10 dB over S9 Variability about the monthly median from ionospheric texts (for
example, Supplement to Report 252-2, CCIR, 1978) Signal power could be from one S-unit higher to two S-units lower
on any given day on this path
S9 to 15 over 9 for this path Rule of thumb actual signal power for any path could be from a
couple S-units higher to several S-units lower than median on anygiven day
Dont make assumptions about your S-meter measure it
S9+10 -63 dBmS9 -73 dBmS8 -78 dBmS7 -83 dBmS6 -88 dBmS5 -93 dBmS4 -98 dBmS3 -103 dBm
S2 -108 dBmS1 -113 dBm
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VOACAP vs W6ELProp
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Whats Different with W6ELProp?
Underlying concept is still the correlation between asmoothed solar parameter and monthly medianionospheric parameters
For foF2, W6ELProp uses equations developed byRaymond Fricker of the BBC VOACAP uses database of numerical coefficients to describe
worldwide ionosphere Another option is IRI (PropLab Pro)
W6ELProp rigorously calculates signal strength using
CCIR methods VOACAP calibrated against actual measurements
For more details on setting up and running W6ELProp, visithttp://mysite.verizon.net/k9la/Downloading_and_Using_W6ELProp.PDF
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Comparison - MUF
K9LA to ZF, October 2003
0
5
10
15
20
25
30
1 3 5 7 9 11 13 15 17 19 21 23
time, UTC
MUF,MH
z
W6ELProp
VOACAP
Close, but there aredifferences especiallyaround sunrise andsunset
The difference is how theF2 region is representedin the model VOACAP is database of
numerical coefficients
Frickers equations inW6ELProp simplified
this to 23 equations (1main function + 22modifying functions)
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Comparison Signal Strength
In generalW6ELProppredicts highersignal strengths
VOACAP ismore realisticwith respect tosignal strength
K9LA to ZF, October 2003
-90
-85
-80
-75
-70
-65
-60-55
-50
-45
-40
1 3 5 7 9 11 13 15 17 19 21 23
time, UTC
signalpower,d
Bm
W6ELProp
VOACAP
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The Mapping Feature in W6ELProp
This is a great tool for low band operating Recently on the topband reflector SM2EKM told
of a 160m QSO with KH6AT in late December at
local noon Without digging any farther, this sounds like a
very unusual QSO
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SM to KH6 in Dec at SM Noon
Path on SM end isperpendicular to theterminator RF from SM
encounters the Dregion right aroundthe terminator
But the solar zenithangle is high
Rest of path is indarkness
A index and K indexare important for thisover-the-pole path Were at zero for a
couple days
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Summary
We dont have daily predictions Predictions are statistical over a months time frame All prediction software is based on the correlation between a
smoothed solar index and monthly median ionospheric parameters Many good programs out there with different presentation formats
and different bells and whistles Dont forget the predictions in the 21st Edition of the ARRL Antenna
Book CD by Dean N6BV VOACAP predictions to/from more than 170 locations Only give signal strength and dont include the WARC bands
Choose the one you like the best
VOACAP considered the standard Several use the VOACAP engine
Interested in validating a prediction? Visit mysite.verizon.net/k9la/Validating_Propagation_Predictions.pdf
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Q & A
This PowerPoint presentation is at http://mysite.verizon.net/k9la
And stay tuned for another PVRCpropagation webinar the topic will be
Disturbances to Propagation
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