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Knowing the terminology used in HF radio propagation can help you understand long-distance communication via skywaves.
Find below a glossary of basic terms and an extended index of terms related to HF radio propagation:
A glossary of basic terms
- Frequency (f): The number of cycles of a radio wave that occur in one second, measured in Hertz (Hz).
- Wavelength (λ): The distance between two consecutive points in a wave, usually measured in meters (m). In radio, wavelength and frequency are inversely related: longer wavelengths correspond to lower frequencies, and vice versa.
- Ionosphere: A region of the Earth's upper atmosphere (approximately 30 to 250 miles above the surface) where ionization occurs due to solar radiation. The ionosphere plays a crucial role in HF radio propagation by reflecting and refracting radio waves.
- Skywave Propagation: The phenomenon in which HF radio waves are refracted back to Earth's surface by the ionosphere. This allows for long-distance communication beyond the line of sight.
- Ground Wave Propagation: Radio waves that travel along the Earth's surface, providing communication over relatively short distances, typically up to a few hundred miles.
- Skip Distance: The minimum distance from the transmitter at which a radio wave can be received after undergoing skywave propagation. This distance depends on the frequency and angle of incidence.
- Skip / Blind / Dead Zone : The region between the ground wave coverage area and the first hop of the skywave propagation, where reception is poor or nonexistent.
- MUF (Maximum Usable Frequency): The highest frequency at which skywave propagation is reliably achievable between two points on Earth during a specific time and under specific ionospheric conditions.
- LUF (Lowest Usable Frequency): The lowest frequency at which skywave propagation is reliably achievable under specific ionospheric conditions.
- Fading: The variation in signal strength and quality experienced during radio transmission due to changes in ionospheric conditions, interference, or other factors.v
- D-layer: The lowest layer of the ionosphere, located at an altitude of approximately 30 to 60 miles. The D-layer absorbs HF radio waves during daylight hours, affecting propagation.
- E-layer: Located above the D-layer, the E-redion is responsible for sporadic E-skip propagation, which can enable HF communication at higher frequencies.
- F-layer: The F-region of the ionosphere consists of two sub-layers, F1 and F2, and is the primary region for HF propagation. The F2 layer is particularly important for long-distance communication.
- Critical Frequency (fc): The highest frequency that can be transmitted vertically and still return to Earth via skywave propagation.
- Optimum Working Frequency (OWF): The frequency that provides the best propagation conditions for a given HF communication path.
- Solar Flux Index (SFI): A measure of the sun's radio emissions at a specific wavelength (usually 10.7 cm). It is used as an indicator of solar activity, which affects ionospheric conditions and HF propagation.
- A-index: A daily measure of geomagnetic activity on a scale from 0 to 400, with lower values indicating quieter geomagnetic conditions. Geomagnetic activity can disrupt HF propagation.
Extended index of terms
An alphabetical list of terms addressed on this website:
- A-Index
- Absorption
- ACE - Advanced Composition Explorer
- Amateur Radio
- Amateur Radio Bands
- Amateur Radio Propagation today
- Angle Elevation/Transmission
- Applications for analyzing and forecasting HF propagation
- Applications used for forecasts and predictions (references)
- Aurora
- Band Conditions
- Beacons
- Blackouts
- Blind zone
- Bt - total strength of the Interplanetary Magnetic Field (IMF)
- Bz - orientation of the IMF
- Can HF Radio Propagation be predicted?
- Carrington Event
- ChatGPT learns about forecasting tools for radio amateurs
- Chirping
- Clouds of plasma in the ionosphere
- CME - Coronal Mass Ejection
- Compare DR2W propagation tool with VOACAP
- Compare forecasting tools for HF radio propagation
- Compare forecasting tools for radio amateurs
- Communication conditions
- Complex HF Propagation Modes
- Conductive ground
- Coronal Mass Ejection (CME)
- Current Band Conditions
- Current Ham Radio Conditions
- Current HF Band Conditions Maps for Radio Operators
- Current HF Band Conditions Online Map
- Current HF Radio Conditions Overview
- Current HF Propagation Conditions
- Current HF Radio Propagation
- Current Propagation Conditions
- Current Shortwave Propagation Conditions
- Current Solar Activity
- Current Solar Events
- Critical Frequency Map
- D-layer
- Dead Zone
- Digisonde Directogram
- Direct Wave propagation
- DX Clusters DX Spots
- DX Propagation map
- DX propagation Online Map
- DX Propagation Prediction
- DXMAPS
- DXWatch
- DXZone
- E-layer
- Earth Observing System (EOS)
- Earth Magnetic Field
- Electron densities
- Electon Flux (Ef)
- Electromagnetic Radiation
- Electromagnetic Spectrum
- EME Deg - Earth-Moon-Earth Degradation
- EsEU - Sporadic E Europe
- EsNA - Sporadic E North America
- EUV sunlight
- FAQ about HF Propagation
- F10.7
- F-layer
- Flare (Solar physics)
- foF2 - critical frequency
- foF2 map
- Forecast HF Propagation Conditions
- Forecast HF Radio Propagation - Applications
- Forecast propagation for radio amateurs
- Forecast vs Prediction of HF Band Conditions
- Forecasting HF Propagation for Radio Amateurs
- Forecasting MUF for a 3000 Km path
- Forecasting Tools For Radio Amateurs
- G1-G5 - scale of Geomagnetic storms
- Gamma Rays
- "GeoMag" (index) - Earth`s Geomagnetic Field Activity
- Geomagnetic
- Geomagnetic Conditions
- Geomagnetic Field Activity
- Geomagnetic Indices
- Geomagnetic Storm
- Geophysical Activity
- Global and Regional HF propagation Conditions
- Global Conditions
- Global HF Propagation
- Global Radio Propagation Conditions
- Greyline Propagation
- Ground Wave
- Ground Wave Propagation
- Ground Waves
- Groundwave
- Hale cycle
- Ham Bands' Activity
- Ham Propagation Map
- Ham Radio Propagation Conditions
- Ham Radio HF Propagation (Real-time)
- Helium Lines
- HF bands allocated for radio amateurs
- HF bands allocated for radio amateurs and their characteristics
- HF Band Conditions
- HF Band Conditions Maps
- HF Bands Info affected by Solar Conditions
- HF Bands Monitoring
- HF Conditions
- HF Propagation
- HF Propagation App
- HF Propagation Blackout
- HF Propagation Calculator
- HF Propagation Chart
- HF Propagation Conditions
- HF propagation conditions at a glance
- HF Propagation Experts
- HF Propagation Explained
- HF Propagation Fadeouts
- HF propagation for radio amateurs
- HF propagation for radio hams
- HF Propagation Forecast for Radio Amateurs
- HF Propagation Forecast tools
- HF Propagation: Fundamentals
- HF Propagation Live Map
- HF Propagation Map
- HF Propagation Online Map
- HF Propagation Overview
- HF Propagation Predictions
- HF Propagation Prediction Online
- HF Propagation Prediction Software
- HF Propagation Model
- HF Propagation Modes
- HF Propagation Now (Real-time)
- HF Propagation Reporter
- HF Propagation Status
- HF Propagation: The Basics
- HF Propagation today
- HF Propagation Tools
- HF radio propagation tutorial for radio amateurs
- HF propagation widget
- HF Radio Conditions
- HF Radio Propagation -
Global Conditions and Regional conditions
- HF Wave Propagation
- HF Radio Propagation Forecast
- HF Radio Propagation Forecasting
- HF Radio Propagation Forecasts
- HF Radio Propagation Today
- HF Radio Waves
- HF Radio Propagation Prediction
- HF Skywave Propagation For Radio Amateurs
- Helium Lines
- High Frequency
- How are HF signals propagated?
- How Can We Forecast HF Propagation Conditions?
- How do the seasons affect HF radio propagation?
- How do you read HF band conditions?
- How does HF propagation work?
- How does the ionosphere affect HF Radio Propagation?
- How to predict MUF?
- IMF - Interplanetary Magnetic Field
- Important frequencies relevant to skywaves
- Incident angle
- Interplanetary Magnetic Field (IMF)
- Introduction to HF propagation
- Ionisation
- Ionization
- Ionogram
- Ionosonde
- Ionosphere
- Ionosphere Layers
- Ionosphere Propagation Of Radio Waves
- Ionosphere, radio waves
- Ionosphere Probing
- Ionospheric Absorption
- "Ionospheric clouds"
- Ionospheric disturbances
- Ionospheric layers summary
- Ionospheric propagation
- Ionospheric reflection
- Ionospheric refraction
- Ionospheric skywave propagation
- Ionospheric storm
- ITU model
- K Index
- Kp index
- KiwiSDR map of remote public SDR receivers accessible via the Internet
- Lagrange Points
- Layers of ionization
- Line-Of-Sight propagation (LOS)
- Live HF propagation map
- Long-distance communication
- Live solar events and past solar activity
- LOS
- LOS - Line of sight propagation
- LUF - Lowest Usable Frequency
- Magnetic Field
- Magnetosphere (MS)
- Mode of Radio Propagation
- Monitor Band Activity of Radio Amateurs
- Monitring HF propagation
- Maximum Usable Frequency (MUF)
- MS - Meteor Scatter Activity
- MUF = Maximum Usable Frequency
- MUF Indicators
- MUF Factor
- MUF 3000 Km Map
- MUF Propagation map by KC2G
- MUF Propagation Online Map
- Near real-time regional maps
- NOAA
- Noise level
- NVIS map
- NVIS propagation
- NVIS tutorial
- Observations - Geo (Terrestrial) & Solar
- On-Line HF Propagation Prediction
- Online propagation tools
- Optimal Sending Frequency
- OWF - Optimum Working Frequency
- Plasma
- "Plasma clouds"
- Polar cap absorption (PCA)
- Practical applications
- Predict conditions
- Predict propagation
- Predict skywave propagation now
- Predict sunspot numbers
- Prediction of sky-wave propagation conditions
- Predicting propagation
- Prediction vs Forecast of HF Band Conditions
- Propagation conditions
- Propagation DX
- Propagation forecast
- Propagation modes
- Propagation of high frequency radio waves
- Propagation of shortwave radio
- Proton Flux
- Propagation | modes of HF radio propagation
- Propagation forecast
- propagation of high frequency radio waves | the rebirth of hf
- propagation of radio waves explained
- Propagation prediction
- Propagation prediction programs and forecasts
- Proton flux (Pf)
- PSKR - PSK Reporter
- Quick guide to HF propagation using solar indices
- R1-R5 - scale of Radio Blackouts
- Radio Amateur
- Radio amateurs HF bands charactaristics
- Radio blackout
- Radio frequency
- Radio propagation beacon
- Radio propagation - free software
- Radio propagation forecasting
- Radio propagation online tools
- Radio propagation software
- Radio propagation tool
- Radio wave propagation in the ionosphere
- Radio waves
- Radio Waves Propagation
- Radio Wave propagation model
- Radio-wave HF propagation models
- Radio-wave propagation modes
- Ray tracing (Optics)
- RBN - Reverse Beacon Network
- Real-time activity of radio amateurs
- Real-time band conditions
- Real-time DX data
- Real-time DX propagation conditions
- Real-time HF band conditions
- Real-Time hf propagation charts
- Real-time HF propagation prediction
- Ham radio HF propagation real-time
- Real-time HF propagation reports
- Real-Time MUF and solar indices
- Real-time MUF map
- Real-time propagation and band conditions
- Real-time radio propagation reports
- Real-time reports of HF propagation
- Real-time Reports of Radio propagation
- Real-time reports of space weather
- Real-time space weather reports
- Real-time watching of worldwide hams' activity
- Recent geophysical & solar observations
- Recent MUF distribution
- Recent observations - Geo (Terrestrial) & Solar
- Recent sunspot number
- Regional conditions
- Regional HF conditions
- Regional MUF and solar indices
- Regions of ionization
- Remote sensing of the ionosphere
- Reports of space weather
- S1-S5 - scale of
Solar radiation storms
- SDO - Solar Dynamic Obervatory (NASA)
- SDR - Software Defined Radio
- SDR spectrum
- Seasonal variations in HF radio propagation
- SEP
- SFI - Solar Flux Index
- Shortwave propagation conditions
- Shortwave propagation forecast
- Shortwave radio propagation
- Skip distance
- Skip zone
- Sky wave
- Skywave Propagation
- Skywave propagation conditions
- Skywave propagation forecast
- Software for HF propagation prediction
- Solar activity
- Solar conditions affect HF radio propagation
- Solar cycle
- Solar data
- Solar events
- Solar Energetic Particle (SEP)
- Solar flares
- Solar Flux Index (SFI)
- Solar indices
- Solar observations
- Solar maximum
- Solar minimum
- Solar Particle Event (SPE)
- Solar phenomena
- Solar radiation
- Solar radio flux
- Solar spectra
- Solar storms
- Solar synoptic map
- Solar terminator (i.e. Greyline)
- Solar Wind
- Solar wind reports
- Solar X-Ray (Phenomenon)
- Solar X-ray Imaging system (SXI)
- Solar X-Ray Flux levels
- Space wave
- Space Weather
- Space Weather Forecasts
- Space Weather Events
- Space Weather Prediction Center (NOAA)
- Space Weather Predictions for radio amateurs
- Space Weather Reports
- Space Weather Scales
- SPE
- SWPC = Space Weather Prediction Center (NOAA)
- Sporadic E
- Stratosphere
- Sudden Ionospheric Diaturbance (SID)
- Sunlight
- Sunspots
- Sunspot cycle
- Sunspot number (SSN)
- Sunspots recent days
- Sunspots today
- Surface wave propagation
- Space Weather Prediction Center (NOAA)
- T Index map
- TEC - Total Electron Content
- Terminator line
- Terrestrial geomagnetic indices
- Terrestrial observations
- The Rebirth of Shortwave Radio Communication
- Thermosphere
- Tools for analyzing and forecasting HF propagation
- Total Electron Content
- Troposphere
- Twilight zone
- Ultraviolet
- Understanding Ham Bands Conditions Banner
- Understanding Ham Radio Propagation
- Understanding HF propagation
- Understanding HF Propagation Numbers
- Understanding HF Radio Propagation
- Understanding NVIS
- Understanding Skywave Propagation
- Usable HF frequencies
- Using HF beacon tracking programs
- Variations in HF radio propagation
- Very High Frequency (VHF)
- Very Low Frequency (VLF)
- VHF propagation map
- View HF bands conditions at a glance
- Visualizing HF Propagation
- VOACAP
- Wave propagation
- What are band conditions banners?
- What are geomagnetic indices?
- What are geomagnetic storms?
- What are HF band conditions?
- What are radio blackouts?
- What are radio waves?
- What are solar flares?
- What are solar storms?
- What are sunspots?
- What are The Current HF Propagation Conditions?
- What are the modes of HF radio propagation?
- What are the modes of radio propagation?
- What are the solar indices?
- What are radio waves?
- What are the current HF propagation conditions?
- What are the current Shortwave propagation conditions?
- What are the Geomagnetic Indices?
- What are the modes of HF radio propagation?
- What are the modes of radio propagation?
- What factors influence HF radio propagation?
- What is Earth magnetic field?
- What is Earth Magnetosphere?
- What is greyline propagation?
- What is Hale cycle?
- What is HF radio propagation prediction?
- What is HF wave propagation?
- What is ionization?
- What is MUF??
- What is NVIS?
- What is plasma?
- What is radio propagation?
- What is skywave HF radio propagation?
- What is solar activity?
- What is solar cycle?
- What is solar wind?
- What is space weather?
- What is the current HF propagation?
- What is the current Shortwave propagation conditions?
- What is the difference between Earth Magnetosphere and Earth magnetic field?
- What is the difference between the Greyline and the Solar Terminator?
- What is the difference between Global versus Regional HF propgation conditions?
- What is Total Electron Content? TEC
- Wide-band WebSDR
- Why is HF used for long range communication?
- Why is shortwave used for long range communication?
- World-wide Space Weather agencies & services
- WSPR - Weak Signal Propagation Reporter
- WSPR Live
- WSPR Rocks
- WSPRnet
- X-ray bursts > Blackouts
- X-Ray flux levels (scale)
- X-Ray flares
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Terms related to HF radio propagation
