Download - Wave Propagation
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Wave Propagation
Presented by:
Bob Kenyon - K8LJ
CRES Amateur Radio Club
4/22/2008
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Agenda• Introduction and background
• Basic propagation concepts
• Propagation software overview
• Modeling program examples
• Demo of W6ELProp and Ionoscope
• Open discussion & conclusion
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Primary Propagation Modes• Ground wave
- AM BC band daytime; HF across town
• Space wave- Point to point (ground not involved)
• Sky wave (the focus of this presentation)- Refraction via the ionosphere- Makes world-wide communications possible
•Satellite communications- Artificial propagation (repeater in the sky)
~ 30 mi.
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Other Propagation Modes
• Back scatter and side scatter• Rain scatter• Tropospheric scatter• Tropospheric ducting• Meteor scatter• Gray line (day - night line)• Aurora• Moon bounce
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Some Basic Concepts
• Wave Reflection - Occurs primarily at earth’s surface
• Wave Refraction - Bending that occurs in the ionosphere and elsewhere
• Wave Diffraction - Bending over the earth’s surface or around obstacles
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Reflection and Refraction
=
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Diffraction Around and Over an Object(Not to scale)
....
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Earth
Ionosphere
Stratosphere*
Troposphere
6.5 miles23 miles
250 miles
The Earth and Environs
* Isothermal region
(Not to scale)
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Layers of the Ionosphere(Not to scale)
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Ole Sol (The Sun)
• Visible light (what we can see)• Ultraviolet light (ionizes the F layer)• Soft X-rays (ionizes the E layer)• Hard X-rays (ionizes the D layer - RF sponge)• Solar wind (charged particles that impact the
earth’s magnetic field• Solar flares & coronal mass ejections (CMEs)• Sunspots (increases ionization of the F layer)
A massive nuclear furnace which produces the following:
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The Electromagnetic SpectrumIncreasing Wavelength Increasing Frequency
OpticalWindow
RadioWindow
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Solar Flare Ionospheric Effects
ElectromagneticRadiation Increase
Delay 8. 3 min
UltravioletAnd X-Rays
D-LayerIncrease (SWF)
Solar Cosmic RaysDelay 15 min – Several
Hours
High Energy Protons & Particles
D –LayerIncrease (PCA)
Magnetic StormParticles
Delay 20-40 Hrs
Low Energy ProtonsAnd Electrons
MagneticStorms
Auroras SporadicE
D – Layer Increase(Auroral Absorption)
Sun
SWF = Short Wave Fading PCA = Polar Cap Absorption
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Some Propagation Terms
• Critical Frequency
The highest frequency returned to earth when transmitted vertically • Critical Angle
The highest angle at a given frequency which will be returned to earth
• Maximum Useable Frequency (MUF)The highest frequency returned to earth between two specific points
• Skip ZoneArea between the ground wave end and 1st sky wave reception
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Frequency vs. Ionospheric Refraction
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Frequency vs. Critical Angle
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Critical Angle and the Skip Zone
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Close-up View of Actual Sunspot
Taken by NSO Sacramento Peak Vacuum Tower Telescope
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100,000Kilometers
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More Propagation Terms
• Sunspot number (SN)- Weighted average of actual sunspots and groups of sunspots
• Smoothed sunspot number (SSN) - SN averaged over + and - 6 months (13 months)
• Solar flux - Measurement of solar radio noise at 2800 MHz. (10.7 cm)
• K index (Kp index - planetary) - A mid latitude geomagnetic index updated every 3 hours (scale 0 - 9)
• A index (Ap index - planetary) - A daily measure derived from the K index (scale 0 - 400)
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Some General Principals
• Sunspot impact is a long term phenomenon- Observe months and years, not hours or days
• Geomagnetic activity is more short term - Hours or even minutes can be very important
• Use the planetary (Kp and Ap indices)
A K Conditions
0 0 Quiet2 1 Quiet3 1 Quiet4 1 Quiet to unsettled7 2 Unsettled15 3 Active27 4 Active48 5 Minor storm80 6 Major storm132 7 Severe storm208 8 Very major storm400 9 Very major storm
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Guide to Propagation Conditions Using Solar Indices
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Smoothed Solar Flux vs. Smoothed Sunspot Number (SSN)
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Penticton, B.C. 10.7 cm Solar Flux Monitoring Facility (2800 Mhz)
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Smoothed Solar Flux vs. Smoothed Planetary A Index
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Last Sunspot Cycle (23)
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Comparison of Last Three Solar Cycles (21, 22, & 23)
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400 Years of Sunspot Observations
Pilgrims Landat
Plymouth Rock
AmericanRevolution
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Solar Cycle 24 Sunspot Number Prediction
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Future Sunspot Cycle Predictions
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Propagation Software
Public Domain (Free)
• W6ELProp V2.7 (demo next)
• VOACAP
Commercial • ASAPS V. 4 $275
• HFx V. 1.1 $129 • CAPMan $89
• WinCAP Wizard 2 $29.95
• PropLab Pro $150
(Sample)
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Demonstration
of
W6ELProp V2.7
and
Ionoscope
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Conclusion
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(1) Davies, K., Ionosopheric Radio, London: Peter Pereginus, 1989.
(2) The ARRL Antenna Book, Newington, CT: ARRL, 2002
(3) Jeffrey S. Beasley & Gary M. Miller, Modern Electronic Communication, 9th Edition, Columbus, OH: Prentice Hall, 2008
(4) Jacobs, G., Cohen, T., Rose, R., The NEW Shortwave Propagation Handbook, CQ Communications, Inc., Hicksville, NY: 1995
(5) The ARRL Handbook, Newington, CT: ARRL, 2002
(6) McNamera, L.F., Radio Amateur’s Guide to the Ionosphere, Malabar, FL: Krieger Publishing Co., 1994
References