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HF (High Frequency) radio propagation, used for long-distance communication, involves several key concepts and terminology. Knowing this terminology can help you understand long-distance communication via skywaves.
Find below a glossary of basic terms and an extended index of terms, all related to HF radio propagation:
A glossary of basic terms
- Frequency (f) is the number of cycles of a radio wave that occur in one second, measured in hertz (Hz).
- Wavelength (λ) is the distance between two consecutive points in a wave, usually measured in meters (m).
The relationship between wavelength and frequency is inverse, with higher frequencies corresponding to shorter wavelengths and vice versa.
- Groundwave propagation is the use of radio waves that travel along the earth's surface, providing communication over relatively short distances, typically up to a few hundred kilometers; effective below 1 MHz, over salty smooth seawater, or conductive ground, but ineffective above 2 MHz.
- Skywave propagation is the phenomenon in which HF radio waves are bounced back to earth's surface, via the ionosphere, allowing long-distance communication beyond the line of sight.
- The ionosphere is the region of the earth's upper atmosphere (approximately 50 to 800 kilometers above the ground) where ionization occurs due to solar radiation. This region plays a crucial role in HF radio propagation by bouncing radio waves back to Earth. The ionosphere is continuously changing due to natural storms, as explained below:
A storm represents a disrupted state of the natural environment, characterized by significant disruptions to normal conditions. In this project, we specifically refer to:
- Solar storms occur on the sun.
- Space weather storms occur in the space between the sun and Earth.
- Geomagnetic storms (also known as magnetic storms) are temporary disturbances of the Earth's magnetosphere caused by a solar wind shock wave.
- Ionospheric storms involve varying densities of energized free electrons in the ionosphere due to geomagnetic storms.
Understanding the dynamics of solar and space weather storms reveals the intricate relationship between our sun and Earth. Solar storms, originating on the sun, unleash powerful energy that travels through space, affecting not only the celestial environment but also our planet's magnetic field. When these solar winds encounter Earth's atmosphere, they can trigger geomagnetic storms, which are temporary disturbances that disrupt communication systems and power grids. Additionally, the presence of energized free electrons in the ionosphere gives rise to ionospheric storms, further complicating our technological landscape.
- Skip distance is the minimum distance from the transmitter for receiving skywaves, while blind, or dead zone, refers to the region with poor or nonexistent reception.
- MUF (Maximum Usable Frequency) is 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) is the lowest frequency at which skywave propagation can be used effectively.
- Fading (QSB) is the variation in signal strength and clarity experienced during radio transmission due to changes in ionospheric conditions, interference, or other factors.
- The F-region is the upper region of the ionosphere that consists of two sub-regions, F1 and F2, and is the primary region for HF propagation. The F2 is particularly important for long-distance communication.
- The E-region is the middle region located below the F-region. It is responsible for sporadic E propagation, which can enable HF communication at higher frequencies.
- The D-region is the lowest region of the ionosphere, located at an altitude of approximately 48 to 90 kilometers. The D-region absorbs HF radio waves during daylight hours, affecting propagation.
- The ionosphere bounces a radio wave at vertical incidence below the critical frequency (fc), regardless of transmitter power.
- The Optimum Working Frequency (OWF) is the frequency that provides the best propagation conditions for a given HF communication path.
- The Solar Flux Index (SFI) is 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.
- The A-index is 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.
- The K-index represents short-term (3-hour) geomagnetic activity at a specific geomagnetic station. It quantifies disturbances in Earth’s horizontal magnetic field by comparing geomagnetic fluctuations, measured by a magnetometer, to a quiet day. The K-scale is logarithmic, a scale from 0 to 9.
Extended index of terms
A list of terms that are explained on this website in alphabetical order:
A
- A-Index
- A collection of books, articles, and presentations on HF propagation
- Absorption of skywaves
- ACE - Advanced composition explorer
- ALE — Automatic link establishment
- Amateur radio
- Amateur radio bands
- Amateur radio operators in the world
- Amateur radio propagation today
- Amateur radio publications: books, articles, and presentations on HF propagation
- Angle elevation/transmission
- Applications for analyzing and forecasting HF propagation
- Applications used for forecasts and predictions (references)
- Aurora
B
- Band activity
- Band conditions
- Band conditions banners
- Band openings
- Band plan
- Beacons
- Beyond line of site (BLOS)
- Blackouts; R1-5 scale
- Blind zone
- BLOS (Beyond line of site)
- Bt - total strength of the Interplanetary Magnetic field (IMF)
- Bz - orientation of the IMF
C
- 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 global ham band conditions
- Current ham band conditions
- Current ham band propagation
- Current ham radio conditions
- Current HF band conditions maps for radio operators
- Current HF band conditions online map
- Current HF bands conditions—charts for radio hams
- Current HF propagation
- Current HF propagation conditions
- Current HF radio propagation
- Current LUF
- Current maximum useable frequency
- Current minimum useable frequency
- Current MUF
- Current propagation
- Current propagation conditions
- Current regional ham band conditions
- Current shortwave propagation conditions
- Current solar activity
- Current solar events
- Critical frequency
- Critical frequencies concept
- Critical frequency map
D
- D-region
- Dead zone
- Digisonde directogram
- Direct wave propagation (LOS - Line Of Site)
- DRAP
- Ducting
- DX clusters
- DX propagation map
- DX propagation online map
- DX propagation prediction
- DX Spots
- DXlook
- DXMAPS
- DXWatch
E
- E-region
- Earth's magnetic field
- Earth's Magnetosphere
- Earth Magnetosphere vs Earth's magnetic field
- Earth observing system (EOS)
- Earth's magnetic field
- Effects of solar activity on amateur radio
- Electron densities
- Electron flux (Ef)
- Electromagnetic Radiation
- Electromagnetic Spectrum
- Electromagnetic Wave
- Electromagnetic Spectrum
- Electromagnetic Radiation
- Electromagnetic Wave
- Elevation Angle
- EME Deg - earth-Moon-Earth Degradation
- EsEU - Sporadic e europe
- EsNA - Sporadic e North America
- EUV sunlight
F
- Factors affecting HF propagation
- FAQ: HF propagation
- FAQ: Current HF propagation conditions
- F10.7
- F-region
- Flare
- foF2 - critical frequency
- foF2 map
- Forecast HF propagation conditions
- Forecast HF radio propagation - applications
- Forecast propagation
- 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
- Free Electron Density
G
- G1-G5 - scale of Geomagnetic storms
- Gamma rays
- Gama rays bursts (GRB)
- GRB - Gama-rays bursts
- "GeoMag" (index) - earth`s agnetic field activity GMF activity
- Geomagnetic
- Geomagnetic activity | What is Geomagnetic activity
- Geomagnetic conditions
- Geomagnetic data
- Geomagnetic field activity
- Geomagnetic indices K, A
- Geomagnetic storms and HF communications
- Geomagnetic storms; G1-5 scale
- Global conditions
- Global HF propagation
- Global radio propagation conditions
- Greyline
- Greyline radio propagation explained
- Greyline vs "Solar Terminator"
- Ground wave
- Ground wave propagation
- Ground waves
H
- HAARP Project for Radio Hams
- Hale cycle
- Ham Activity
- Ham Band Conditions | Ham band conditions
- Ham bands' activity
- Ham conditions
- Ham propagation
- Ham propagation map
- Ham radio bands
- Ham radio bands and frequencies | Ham radio bands & frequencies
- Ham radio communications
- Ham radio conditions map
- Ham radio frequency chart
- Ham radio HF propagation (real-time)
- Ham radio propagation conditions
- Ham radio propagation tutorial
- Ham radio operators in the world
- Ham Radio Range
- Ham solar
- 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 Radio Propagation Basics
- 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 explanation
- HF propagation fadeouts
- HF propagation for beginners and advanced radio hams
- HF propagation for radio amateurs
- HF propagation for radio hams
- HF propagation forecast for radio amateurs
- HF propagation forecast tools
- HF Propagation Forecasting
- HF propagation: fundamentals
- HF propagation live map
- HF propagation map
- HF propagation modeling
- HF propagation models
- HF propagation modes
- HF propagation online map
- HF propagation overview
- HF propagation now (real-time)
- HF propagation predictions
- HF propagation prediction online
- HF propagation prediction software
- HF propagation preface
- HF propagation reporter
- HF propagation Status
- HF propagation status and alerts
- HF propagation — The basics
- HF Propagation Today
- HF Propagation Tools
- HF radio propagation indices and scales
- HF radio propagation prediction
- HF radio propagation tutorial for radio amateurs
- HF propagation widget
- HF radio conditions
- HF radio propagation
- HF signals propagation
- HF skywave window: LUF—MUF
- HF radio propagation forecast
- HF radio propagation today
- HF radio wave propagation
- HF radio waves (basics)
- HF radio wave propagation factors
- HF radio propagation prediction
- HF real time propagation reports
- HF skywave propagation for radio amateurs
- HF wave propagation
- HFTA - High frequency Terrain Assessment
- Helium lines
- High frequency
- Highest Possible Frequency (HPF)
- How radio waves propagate
- How radio waves travel
- How skywave propagation works
- HPF—Highest Possible Frequency
I
- IMF - Interplanetary Magnetic field
- Impacts of space weather
- Incident angle
- Interplanetary Magnetic field (IMF)
- Introduction to HF propagation
- Ionisation
- Ionization
- Ionogram
- Ionosonde
- Ionosphere
- Ionosphere and HF radio propagation
- Ionosphere propagation of radio waves
- Ionosphere regions
- Ionosphere, radio waves
- Ionosphere probing
- Ionosphere regions
- Ionospheric absorption—D-region
- Ionospheric bubbles
- Ionospheric clouds
- Ionospheric conditions
- Ionospheric data
- Ionospheric disturbances
- Ionospheric irregularities
- Ionospheric propagation
- Ionospheric refraction
- Ionospheric regions
- Ionospheric skywave propagation
- Ionospheric storms
- IRI ionospheric model
- ITU model
K
- K-Index
- Key concepts of HF propagation
- Key Factors Affecting HF Propagation
- Kp index
- KiwiSDR map of remote public SDR receivers accessible via the Internet
L
- Lagrange points
- Latest HF Bands Propagation
- Learning about space weather
- Line of sight propagation (LOS)
- Live HF propagation map
- Local HF propagation conditions vs. global forecast
- Local HF conditions matter more than global conditions
- Long-distance communication
- Live solar events and past solar activity
- LOS
- LOS - Line of sight propagation
- LUF - Lowest Usable frequency
- LUF Chart - The Lowest Usable frequency map
M
- Magnetic field
- Magnetosphere (MS)
- Maximum usable frequency (MUF)
- Maximum usable frequency map
- Minimum usable frequency map
- Modes of HF radio propagation
- Modes of radio propagation
- Monitor band activity of radio amateurs ↗
- Monitor HF propagation
- Monitor propagation conditions
- MS — Meteor Scatter Activity
- MUF — Maximum Usable frequency
- MUF Indicators
- MUF How what, why?
- MUF factor
- MUF map
- MUF propagation map by KC2G for a 3,000 km hop
- MUF propagation online map
- Multipath Propagation
N
- Near real-time regional maps
- Near Vertical Incidence Skywave
- NET ionospheric model
- NOAA National Oceanic and Atmospheric Administration
- Noise level
- NVIS
- NVIS map
- NVIS propagation
- NVIS propagation concept
- NVIS tutorial
O
- Observations - Terrestrial & Solar
- On-Line HF propagation prediction
- Online propagation tools
- Online real-time propagation charts
- Optimal Sending frequency
- OWF - Optimum Working frequency
P
- Past solar activity
- PCA—polar cap absorption
- Plasma
- Plasma clouds
- Polar cap absorption (PCA)
- Practical applications
- Predict conditions
- Predict HF radio propagation
- Predict MUF
- Predict propagation
- Predict skywave propagation now
- Predict sunspot numbers
- Prediction of sky-wave propagation conditions
- Predicting propagation
- Prediction vs forecast of HF band conditions
- Principles of radio wave propagation
- Propagation charts
- Propagation conditions
- Propagation conditions monitoring
- Propagation DX
- Propagation factors and conditions
- Propagation forecast
- Propagation indicators — A review of skywave propagation indicators
- Propagation indices single: propagation index
- Propagation modes
- Propagation of high frequency radio waves
- Propagation of HF radio waves - Global conditions and Regional conditions
- 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
- Propagation report
- Proton flux (Pf)
- PSKR - PSK reporter
Q
- Quick guide to HF propagation using solar indices
R
- Radio
- Radio Amateur
- Radio amateurs HF bands charactaristics
- Radio blackouts / fadeouts; R1-5 scale
- Radio Books on HF Propagation
- Radio Communication Circuit
- Radio frequency
- Radio propagation
- Radio propagation beacon
- Radio propagation conditions today
- Radio propagation explained
- Radio propagation forecast
- Radio propagation free software
- Radio propagation modeling
- Radio propagation models
- Radio propagation online tools
- Radio propagation properties
- Radio propagation software
- Radio propagation tool
- Radio propagation tutorial
- Radio spectrum | Radio spectrum
- 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 HF band activity
- Real time HF band conditions
- Real-time HF band activity
- Real-time HF band conditions
- 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 ham band activity using the internet
- Real-time MUF 3000 km propagation map
- 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 space weather reports
- Real-time watching of worldwide hams' activity
- Real-time watching of worldwide ham activity
- Recent geophysical & solar observations
- Recent HF Bands Propagation
- Recent MUF distribution
- Recent observations - Geo (Terrestrial) & Solar
- Recent sunspot number
- Regional conditions
- Regional HF conditions
- Regional MUF and solar indices
- Regional vs Global HF propgation conditions
- Regional vs Global propgation conditions
- Regions of ionization
- Region vs. Layer: Earth's Atmosphere and Ionosphere
- Remote sensing of the ionosphere
- Reports of space weather
- RSG scales of Space Weather
S
- Satellites for space weather observations
- SDO - Solar Dynamic Obervatory (NASA)
- SDR - Software Defined radio
- SDR spectrum
- Seasonal variations in HF radio propagation
- Seasons affect HF radio propagation
- SEP
- SFI - Solar flux Index
- Shortwave propagation
- Shortwave propagation conditions
- Shortwave propagation forecast
- Shortwave radio propagation
- SID - Sudden ionospheric disturbances
- Significant frequencies relevant to skywaves
- Skip distance
- Skip zone
- Skywave
- Skywave concept
- Skywave HF radio propagation
- Skywave propagation
- Skywave propagation concept
- Skywave propagation conditions
- Skywave propagation for hams explained
- Skywave propagation for radio amateurs
- Skaywave propagation indicators for radio amateurs
- Skaywave propagation indicators for radio hams
- Skywave propagation forecast
- Skywave propagation tutorial
- Software for HF propagation prediction
- Solar activity
- Solar Activity & Ham radio propagation
- Solar activity affects HF propagation
- Solar activity affects skywaves
- Solar activity for radio amateurs
- Solar conditions affect HF radio propagation
- Solar conditions and ham radio propagation
- Solar conditions and HF radio propagation
- Solar cycle
- Solar Cycle Ham Radio
- Solar data
- Solar electromagnetic spectrum
- Solar events
- Solar energetic Particle (SEP)
- Solar events
- Solar flares
- Solar flux
- Solar flux index (SFI)
- Solar flux today
- Solar Ham
- Solar indices
- Solar observations
- Solar maximum
- Solar minimum
- Solar Particle event (SPE)
- Solar phenomena
- Solar propagation
- Solar radiation
- Solar radiation storms (flares); S1-5 scale
- Solar radio flux
- Solar spectra
- Solar storms
- Solar Storms Ham Radio
- Solar synoptic map
- Solar terminator (i.e. Greyline)
- Solar wind; The impact of the solar wind on HF radio transmission.
- Solar wind reports
- Solar X-Ray (Phenomenon)
- Solar X-ray Imaging system (SXI)
- Solar X-Ray flux levels
- Space wave
- Space weather
- Space Weather (HF propagation)
- Space weather data and plots
- Space weather definitions and explanations
- Space weather events
- Space weather forecasts
- Space weather ground-based observatories
- Space weather observations
- Space weather observations from satellites
- Space weather prediction
- Space weather prediction center (NOAA)
- Space Weather predictions for radio amateurs
- Space weather reports
- Space weather scales
- Space weather status and alerts
- SPE
- Spread F
- Sudden ionospheric disturbances
- Sunspots
- SuperDARN
- SWPC = Space Weather prediction center (NOAA)
- Sporadic e
- Stratosphere
- Sudden ionospheric disturbances (SID)
- Sunlight
- Sunspots
- Sunspot cycle
- Sunspot number
- Sunspots recent days
- Sunspots today
- Surface wave propagation
- Space Weather prediction center (NOAA)
- swx — Space Weather Conditions
T
- T Index map
- TEC - Total electron content
- Terminator line
- Terrestrial geomagnetic indices
- Terrestrial observations
- The current solar wind
- The Holy Cluster
- The Rebirth of Shortwave radio communication
- The recent HF propagation conditions
- The recent propagation conditions
- The recent skywave propagation conditions
- The Super Dual Auroral Radar Network (SuperDARN)
- Thermosphere
- TID (Traveling ionospheric disturbances)
- Tools for analyzing and forecasting HF propagation
- Total electron content — TEC
- Transmission Angle
- Traveling ionospheric disturbances (TID)
- Troposphere
- Tropospheric propagation
- Twilight zone
U
- Ultraviolet
Understanding ham band conditions
- Understanding Ham bands conditions banner
- Understanding Ham radio propagation
- Understanding HF propagation
- Understanding HF propagation review
- Understanding HF propagation Numbers
- Understanding HF radio propagation
- Understanding LUF and MUF
- Understanding NVIS
- Understanding Skywave propagation
- Understanding the basics of HF band conditions
- Usable Frequency Range from LUF to MUF
- Usable HF frequencies
- Using HF beacon tracking programs
V
- 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
W
- Wave propagation
- What is ham radio communications
- Wide-band WebSDR
- Window of useful frequencies from LUF to MUF
- World-wide Space Weather agencies & services
- Worldwide LUF chart
- WSPR - Weak Signal propagation reporter * WSPR Live * WSPR Rocks * WSPRnet
X
- X-Ray flares
- X-Ray flux levels (scale)
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HF radio propagation: