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