↑ Terms related to HF radio propagation

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

  1. Frequency (f): The number of cycles of a radio wave that occur in one second, measured in Hertz (Hz).
  2. 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.
  3. 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.
  4. 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.
  5. 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.
  6. 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.
  7. 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.
  8. 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.
  9. LUF (Lowest Usable Frequency): The lowest frequency at which skywave propagation is reliably achievable under specific ionospheric conditions.
  10. Fading: The variation in signal strength and quality experienced during radio transmission due to changes in ionospheric conditions, interference, or other factors.v
  11. 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.
  12. 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.
  13. 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.
  14. Critical Frequency (fc): The highest frequency that can be transmitted vertically and still return to Earth via skywave propagation.
  15. Optimum Working Frequency (OWF): The frequency that provides the best propagation conditions for a given HF communication path.
  16. 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.
  17. 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:

  1. A-Index
  2. Absorption
  3. ACE - Advanced Composition Explorer
  4. Amateur Radio
  5. Amateur Radio Bands
  6. Amateur Radio Propagation today
  7. Angle Elevation/Transmission
  8. Applications for analyzing and forecasting HF propagation
  9. Applications used for forecasts and predictions (references)
  10. Aurora
  11. Band Conditions
  12. Beacons
  13. Blackouts
  14. Blind zone
  15. Bt - total strength of the Interplanetary Magnetic Field (IMF)
  16. Bz - orientation of the IMF
  17. Can HF Radio Propagation be predicted?
  18. Carrington Event
  19. ChatGPT learns about forecasting tools for radio amateurs
  20. Chirping
  21. Clouds of plasma in the ionosphere
  22. CME - Coronal Mass Ejection
  23. Compare DR2W propagation tool with VOACAP
  24. Compare forecasting tools for HF radio propagation
  25. Compare forecasting tools for radio amateurs
  26. Communication conditions
  27. Complex HF Propagation Modes
  28. Conductive ground
  29. Coronal Mass Ejection (CME)
  30. Current Band Conditions
  31. Current Ham Radio Conditions
  32. Current HF Band Conditions Maps for Radio Operators
  33. Current HF Band Conditions Online Map
  34. Current HF Radio Conditions Overview
  35. Current HF Propagation Conditions
  36. Current HF Radio Propagation
  37. Current Propagation Conditions
  38. Current Shortwave Propagation Conditions
  39. Current Solar Activity
  40. Current Solar Events
  41. Critical Frequency Map
  42. D-layer
  43. Dead Zone
  44. Digisonde Directogram
  45. Direct Wave propagation
  46. DX Clusters DX Spots
  47. DX Propagation map
  48. DX propagation Online Map
  49. DX Propagation Prediction
  50. DXMAPS
  51. DXWatch
  52. DXZone
  53. E-layer
  54. Earth Observing System (EOS)
  55. Earth Magnetic Field
  56. Electron densities
  57. Electon Flux (Ef)
  58. Electromagnetic Radiation
  59. Electromagnetic Spectrum
  60. EME Deg - Earth-Moon-Earth Degradation
  61. EsEU - Sporadic E Europe
  62. EsNA - Sporadic E North America
  63. EUV sunlight
  64. FAQ about HF Propagation
  65. F10.7
  66. F area
  67. F layer
  68. F spot
  69. Flare (Solar Physics)
  70. foF2 - Critical Frequency
  71. foF2 map
  72. Forecast HF Propagation Conditions
  73. Forecast HF Radio Propagation - Applications
  74. Forecast propagation for radio amateurs
  75. Forecast vs Prediction of HF Band Conditions
  76. Forecasting HF Propagation for Radio Amateurs
  77. Forecasting MUF for a 3000 Km path
  78. Forecasting Tools For Radio Amateurs
  79. G1-G5 - scale of Geomagnetic storms
  80. Gamma Rays
  81. "GeoMag" (index) - Earth`s Geomagnetic Field Activity
  82. Geomagnetic
  83. Geomagnetic Conditions
  84. Geomagnetic Field Activity
  85. Geomagnetic Indices
  86. Geomagnetic Storm
  87. Geophysical Activity
  88. Global and Regional HF propagation Conditions
  89. Global Conditions
  90. Global HF Propagation
  91. Global Radio Propagation Conditions
  92. Greyline Propagation
  93. Ground Wave
  94. Ground Wave Propagation
  95. Ground Waves
  96. Groundwave
  97. Hale cycle
  98. Ham Bands' Activity
  99. Ham Propagation Map
  100. Ham Radio Propagation Conditions
  101. Ham Radio HF Propagation (Real-time)
  102. Helium Lines
  103. HF bands allocated for radio amateurs
  104. HF bands allocated for radio amateurs and their characteristics
  105. HF Band Conditions
  106. HF Band Conditions Maps
  107. HF Bands Info affected by Solar Conditions
  108. HF Bands Monitoring
  109. HF Conditions
  110. HF Propagation
  111. HF Propagation App
  112. HF Propagation Calculator
  113. HF Propagation Chart
  114. HF Propagation Conditions
  115. HF propagation conditions at a glance
  116. HF Propagation Experts
  117. HF Propagation Explained
  118. HF propagation for radio amateurs
  119. HF propagation for radio hams
  120. HF Propagation Forecast for Radio Amateurs
  121. HF Propagation Forecast tools
  122. HF Propagation: Fundamentals
  123. HF Propagation Live Map
  124. HF Propagation Map
  125. HF Propagation Online Map
  126. HF Propagation Overview
  127. HF Propagation Predictions
  128. HF Propagation Prediction Online
  129. HF Propagation Prediction Software
  130. HF Propagation Model
  131. HF Propagation Modes
  132. HF Propagation Now (Real-time)
  133. HF Propagation Reporter
  134. HF Propagation Status
  135. HF Propagation: The Basics
  136. HF Propagation today
  137. HF Propagation Tools
  138. HF radio propagation tutorial for radio amateurs
  139. HF propagation widget
  140. HF Radio Conditions
  141. HF Radio Propagation - Global Conditions and Regional conditions
  142. HF Radio Propagation Forecast
  143. HF Radio Propagation Today
  144. HF Wave Propagation
  145. HF radio propagation forecasting
  146. HF radio propagation forecasts
  147. HF Radio Waves
  148. HF radio propagation prediction
  149. HF Skywave Propagation For Radio Amateurs
  150. Helium Lines
  151. High Frequency
  152. How are HF signals propagated?
  153. How Can We Forecast HF Propagation Conditions?
  154. How do the seasons affect HF radio propagation?
  155. How do you read HF band conditions?
  156. How does HF propagation work?
  157. How does the ionosphere affect HF Radio Propagation?
  158. IMF - Interplanetary Magnetic Field
  159. Important frequencies relevant to skywaves
  160. Incident angle
  161. Interplanetary Magnetic Field (IMF)
  162. Introduction to HF propagation
  163. Ionisation
  164. Ionization
  165. Ionogram
  166. Ionospheric Reflection
  167. Ionospheric Storm
  168. Ionosonde
  169. Ionosphere
  170. Ionosphere Layers
  171. Ionosphere Propagation Of Radio Waves
  172. Ionosphere, radio waves
  173. Ionosphere Probing
  174. Ionospheric Absorption
  175. Ionospheric Clouds
  176. Ionospheric disturbances
  177. Ionospheric Layers Summary
  178. Ionospheric Propagation
  179. Ionospheric Reflection
  180. Ionospheric Refraction
  181. Ionospheric Skywave propagation
  182. ITU model
  183. K Index
  184. KiwiSDR Remote Public SDR Receivers accessible via the Internet
  185. KiwiSDR world map distribution
  186. Kp index
  187. Lagrange Points
  188. Layers of Ionization
  189. Line-Of-Sight Propagation (LOS)
  190. Live HF Propagation Map
  191. Long Distance Communication
  192. Live Solar Events and Past Solar Activity
  193. LOS
  194. LOS - Line of sight propagation
  195. LUF - Lowest Usable Frequency
  196. Magnetic Field
  197. Magnetosphere (MS)
  198. Mode of Radio Propagation
  199. Monitor Band Activity of Radio Amateurs
  200. Monitring HF propagation
  201. Maximum Usable Frequency (MUF)
  202. MS - Meteor Scatter Activity
  203. MUF = Maximum Usable Frequency
  204. MUF Indicators
  205. MUF Factor
  206. MUF 3000 Km Map
  207. MUF Propagation map by KC2G
  208. MUF Propagation Online Map
  209. Near Real-Time Regional Maps
  210. NOAA
  211. Noise Level
  212. NVIS map
  213. NVIS Propagation
  214. NVIS Tutorial
  215. Observations - Geo (Terrestrial) & Solar
  216. On-Line HF Propagation Prediction
  217. Online propagation tools
  218. Optimal Sending Frequency
  219. OWF - Optimum Working Frequency
  220. Plasma
  221. Plasma Clouds
  222. Polar cap absorption (PCA)
  223. Practical Applications
  224. Predict skywave propagation now
  225. Predicted Sunspot Numbers
  226. Prediction of sky-wave propagation conditions
  227. Predicting Propagation
  228. Prediction vs Forecast of HF Band Conditions
  229. Propagation Conditions
  230. Propagation DX
  231. Propagation forecast
  232. Propagation modes
  233. Propagation of high frequency radio waves
  234. Propagation of Shortwave Radio
  235. Proton Flux
  236. Propagation | modes of HF radio propagation
  237. Propagation Forecast
  238. Propagation of High Frequency Radio Waves | The Rebirth of HF
  239. Propagation of Radio Waves explained
  240. Propagation Prediction
  241. Propagation Prediction Programs and Forecasts
  242. Proton Flux (Pf)
  243. PSK Reporter
  244. PSKR - PSK Reporter
  245. Quick Guide to HF Propagation Using Solar Indices
  246. R1-R5 - scale of Radio Blackouts
  247. Radio Amateur
  248. Radio Amateurs HF Bands Charactaristics
  249. Radio Blackout
  250. Radio frequency
  251. Radio Propagation Beacon
  252. Radio Propagation - Free Software
  253. Radio Propagation Forecasting
  254. Radio Propagation Online Tools
  255. Radio Propagation Software
  256. Radio Propagation Tool
  257. Radio wave propagation in the ionosphere
  258. Radio Waves
  259. Radio Waves Propagation
  260. Radio Wave Propagation Model
  261. Radio-wave HF Propagation Models
  262. Radio-wave Propagation Modes
  263. Ray Tracing (Optics)
  264. RBN - Reverse Beacon Network
  265. Real-time Activity of Radio Amateurs
  266. Real-time Band Conditions
  267. Real-time Data
  268. Real-time DX Propagation Conditions
  269. Real-time HF band conditions
  270. Real-Time HF Propagation Charts
  271. Real-Time HF Propagation Prediction
  272. Ham Radio HF Propagation Real-time
  273. Real-time HF Propagation Reports
  274. Real-Time MUF and Solar Indices
  275. Real-Time MUF Map
  276. Real-time propagation and band conditions
  277. Real-time Radio Propagation Reports
  278. Real-time Reports of HF Propagation
  279. Real-time Reports of Radio Propagation
  280. Real-time Reports of Space Weather
  281. Real-time Space Weather Reports
  282. Real-time watching of worldwide hams' activity
  283. Recent Geophysical & Solar Observations
  284. Recent MUF distribution
  285. Recent Observations - Geo (Terrestrial) & Solar
  286. Recent Sunspot Number
  287. Regional Conditions
  288. Regional HF Conditions
  289. Regional MUF and Solar Indices
  290. Regions of Ionization
  291. Remote sensing of the ionosphere
  292. Reports of Space Weather
  293. S1-S5 - scale of Solar Radiation storms
  294. SDO - Solar Dynamic Obervatory (NASA)
  295. SDR - Software Defined Radio
  296. SDR Spectrum
  297. Seasonal variations in HF radio propagation
  298. SEP
  299. SFI - Solar Flux Index
  300. Shortwave propagation conditions
  301. Shortwave propagation forecast
  302. Shortwave radio propagation
  303. Skip distance
  304. Skip zone
  305. Sky Wave
  306. Skywave Propagation
  307. Skywave propagation conditions
  308. Skywave propagation forecast
  309. Software for HF Propagation Prediction
  310. Solar Activity
  311. Solar Conditions affect HF Radio Propagation
  312. Solar Cycle
  313. Solar Data
  314. Solar Events
  315. Solar Energetic Particle (SEP)
  316. Solar Flares
  317. Solar Flux Index (SFI)
  318. Solar Indices
  319. Solar Observations
  320. Solar maximum
  321. Solar minimum
  322. Solar Particle Event (SPE)
  323. Solar Phenomena
  324. Solar Radiation
  325. Solar Radio Flux
  326. Solar Spectra
  327. Solar Storms
  328. Solar Synoptic Map
  329. Solar Terminator (i.e. Greyline)
  330. Solar Wind
  331. Solar Wind Reports
  332. Solar X-Ray (Phenomenon)
  333. Solar X-ray Imaging System (SXI)
  334. Solar X-Ray Flux levels
  335. Space Wave
  336. Space Weather
  337. Space Weather Forecasts
  338. Space Weather Events
  339. Space Weather Prediction Center (NOAA)
  340. Space Weather Predictions for radio amateurs
  341. Space Weather Reports
  342. Space Weather Scales
  343. SPE
  344. SWPC = Space Weather Prediction Center (NOAA)
  345. Sporadic E
  346. Stratosphere
  347. Sudden Ionospheric Diaturbance (SID)
  348. Sunlight
  349. Sunspots
  350. Sunspot Cycle
  351. Sunspot Number (SSN)
  352. Sunspots Recent Days
  353. Sunspots Today
  354. Surface wave propagation
  355. Space Weather Prediction Center (NOAA)
  356. T Index Map
  357. TEC - Total Electron Content
  358. Terminator line
  359. Terrestrial Geomagnetic Indices
  360. Terrestrial Observations
  361. The Rebirth of Shortwave Radio Communication
  362. Thermosphere
  363. Tools for analyzing and forecasting HF propagation
  364. Total Electron Content
  365. Troposphere
  366. Twilight zone
  367. Ultraviolet
  368. Understanding Ham Bands Conditions Banner
  369. Understanding Ham Radio Propagation
  370. Understanding HF Propagation
  371. Understanding HF Propagation Numbers
  372. Understanding HF Radio Propagation
  373. Understanding NVIS
  374. Understanding Skywave Propagation
  375. Usable HF Frequencies
  376. Using HF Beacon Tracking Programs
  377. Variations in HF radio propagation
  378. Very High Frequency (VHF)
  379. Very Low Frequency (VLF)
  380. VHF Propagation Map
  381. View HF Bands Conditions at a glance
  382. Visualizing HF Propagation
  383. VOACAP
  384. Wave Propagation
  385. What are Band Conditions Banners?
  386. What are Geomagnetic Indices?
  387. What are Geomagnetic Storms?
  388. What are HF Band Conditions?
  389. What are Radio Blackouts?
  390. What are Radio Waves?
  391. What are Solar Flares?
  392. What are Solar Storms?
  393. What are Sunspots?
  394. What are The Current HF Propagation Conditions?
  395. What are The Modes of HF Radio Propagation?
  396. What are The Modes of Radio Propagation?
  397. What are the Solar Indices?
  398. What are radio waves?
  399. What are the current HF propagation conditions?
  400. What are the current Shortwave propagation conditions?
  401. What are the Geomagnetic Indices?
  402. What are the modes of HF Radio Propagation?
  403. What are the modes of Radio Propagation?
  404. What factors influence HF Radio Propagation?
  405. What is Earth Magnetic field?
  406. What is Earth Magnetosphere?
  407. What is Greyline propagation?
  408. What is Hale cycle?
  409. What is HF Radio Propagation Prediction?
  410. What is HF Wave Propagation?
  411. What is Ionization?
  412. What is NVIS?
  413. What is Plasma?
  414. What is Radio Propagation?
  415. What is Skywave HF Radio Propagation?
  416. What is Solar Activity?
  417. What is Solar cycle?
  418. What is Solar Wind?
  419. What is Space Weather?
  420. What is the current HF propagation?
  421. What is the current Shortwave propagation conditions?
  422. What is the difference between Earth Magnetosphere and Earth Magnetic field?
  423. What is the difference between the Greyline and the Solar Terminator?
  424. What is the difference between Global versus Regional HF propgation conditions?
  425. What is Total Electron Content? TEC
  426. Wide-Band WebSDR
  427. Why is HF used for long range communication?
  428. Why is Shortwave used for long range communication?
  429. World Wide Space Weather Agencies & Services
  430. WSPR - Weak Signal Propagation Reporter
  431. WSPR Live
  432. WSPR Rocks
  433. WSPRnet
  434. X-ray bursts > Blackouts
  435. X-Ray Flux levels
  436. X-Ray flares
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