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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. Groundwave 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.v
  7. Skip Zone / Dead Zone : The region between the groundwave 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-layer is responsible for sporadic E-skip propagation, which can enable HF communication at higher frequencies.
  13. F-layer: The F-layer of the ionosphere consists of two sub-layers, F1 and F2, and is the primary layer 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

The following is an alphabetical list of terms related to HF radio propagation:

  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 used for forecasts and predictions
  9. Aurora
  10. Band Conditions
  11. Beacons
  12. Blackouts (due to X-ray bursts)
  13. Bt - total strength of the Interplanetary Magnetic Field (IMF)
  14. Bz - orientation of the IMF
  15. Can HF Radio Propagation be predicted?
  16. Carrington Event
  17. ChatGPT learns about forecasting tools for radio amateurs
  18. Chirping
  19. CME - Coronal Mass Ejection
  20. Compare DR2W propagation tool with VOACAP
  21. Compare forecasting tools for HF radio propagation
  22. Compare forecasting tools for radio amateurs
  23. Communication conditions
  24. Complex HF Propagation Modes
  25. Conductive ground
  26. Current Band Conditions
  27. Current HF Band Conditions
  28. Current HF Propagation Conditions
  29. Current HF Radio Propagation
  30. Current Propagation Conditions
  31. Current HF Radio Conditions
  32. Critical Frequency Map
  33. D-layer
  34. Dead Zone
  35. Digisonde Directogram
  36. Direct Wave propagation
  37. DX Clusters DX Spots
  38. DX Propagation map
  39. DX propagation map online
  40. DX Propagation Prediction
  41. DXMAPS
  42. DXWatch
  43. DXZone
  44. E-layer
  45. Earth's Magnetic Field
  46. Electron densities
  47. Electon Flux (Ef)
  48. Electromagnetic Radiation
  49. Electromagnetic Spectrum
  50. EME Deg - Earth-Moon-Earth Degradation
  51. EsEU - Sporadic E Europe
  52. EsNA - Sporadic E North America
  53. EUV sunlight
  54. FAQ about HF Propagation
  55. F10.7
  56. F-layer
  57. foF2 - Critical Frequency
  58. foF2 map
  59. Forecast HF Propagation Conditions
  60. Forecast HF Radio Propagation - Applications
  61. Forecast propagation for radio amateurs
  62. Forecasting HF Propagation for Radio Amateurs
  63. Forecasting MUF for a 3000 Km path
  64. Forecasting Tools For Radio Amateurs
  65. G1-G5 sacale of Geomagnetic storms
  66. GeoMag - Earth`s Geomagnetic Field Activity
  67. Geomagnetic Conditions
  68. Geomagnetic Field Activity
  69. Geomagnetic Indices
  70. Geomagnetic Storms
  71. Geophysical Activity
  72. Global Conditions
  73. Global HF Propagation
  74. Global and Regional HF propagation Conditions
  75. Greyline Propagation
  76. Ground Wave
  77. Ground Wave Propagation
  78. Ground Waves
  79. Groundwave
  80. Hale cycle
  81. Ham Bands' Activity
  82. Ham Radio Propagation Conditions
  83. Ham Radio HF Propagation Real Time
  84. Helium Lines
  85. HF Band Conditions
  86. HF Band Conditions Maps
  87. HF Bands Info affected by Solar Conditions
  88. HF Bands Monitoring
  89. HF Conditions
  90. HF propagation
  91. HF Propagation App
  92. HF Propagation Calculator
  93. HF Propagation Chart
  94. HF Propagation Conditions
  95. HF propagation conditions at a glance
  96. HF propagation explained
  97. HF propagation for radio amateurs
  98. HF propagation for radio hams
  99. HF Propagation Forecast for Radio Amateurs
  100. HF Propagation Forecast tools
  101. HF Propagation Live Map
  102. HF Propagation Map
  103. HF propagation modes
  104. HF Propagation Predictions
  105. HF Propagation Prediction Online
  106. HF Propagation Prediction Software
  107. HF Propagation Map Online
  108. HF Propagation Model
  109. HF Propagation Modeling
  110. HF Propagation Modes
  111. HF Propagation Real Time
  112. HF Propagation Reporter
  113. HF Propagation today
  114. HF radio propagation tutorial for radio amateurs
  115. HF propagation widget
  116. HF Radio Propagation - Global Conditions and Regional conditions
  117. HF Radio Propagation For Radio Amateurs
  118. HF Radio Propagation Today
  119. HF Wave Propagation
  120. HF radio propagation forecasting
  121. HF radio propagation forecasts
  122. HF Radio Waves
  123. HF radio propagation prediction
  124. Helium Lines
  125. How are HF signals propagated?
  126. How Can We Forecast HF Propagation Conditions?
  127. How do the seasons affect HF radio propagation?
  128. How do you read HF band conditions?
  129. How does the ionosphere affect HF Radio Propagation?
  130. IMF - Interplanetary Magnetic Field
  131. Important frequencies relevant to skywave
  132. Incident angle
  133. Introduction to HF propagation
  134. Ionisation
  135. Ionization
  136. Ionogram
  137. Ionosonde
  138. Ionosphere
  139. Ionosphere Definition
  140. Ionosphere Facts
  141. Ionosphere Layers
  142. Ionosphere Propagation Of Radio Waves
  143. Ionosphere, radio waves
  144. Ionosphere Probing
  145. Ionospheric Clouds
  146. Ionospheric disturbances
  147. Ionospheric Layers (summary)
  148. Ionospheric Propagation
  149. Ionospheric Reflection
  150. Ionospheric Refraction
  151. Ionospheric Skywave propagation
  152. K-Index
  153. KiwiSDR
  154. KiwiSDR map
  155. Lagrange Points
  156. Layers of Ionization
  157. Line-Of-Sight (LOS)
  158. Live HF Propagation Map
  159. Live Solar Activity
  160. Live Solar Events
  161. Long Distance Communication
  162. Live Solar Events and Past Solar Activity
  163. LOS
  164. LOS - Line of sight propagation
  165. LUF - Lowest Usable Frequency
  166. Magnetic Field
  167. Magnetosphere (MS)
  168. Measuring HF propagation
  169. Mode of Radio Propagation
  170. Monitring HF propagation
  171. Maximum Usable Frequency (MUF)
  172. MS - Meteor Scatter Activity
  173. MUF = Maximum Usable Frequency
  174. MUF Indicators
  175. MUF Factor
  176. MUF 3000 Km Map
  177. MUF Propagation map by KC2G
  178. MUF Propagation Map Online
  179. Near Real-Time Regional Maps
  180. NOAA
  181. Noise Level
  182. NVIS map
  183. NVIS Propagation
  184. Observations - Geo (Terrestrial) & Solar
  185. Online propagation tools
  186. OWF - Optimum Working Frequency
  187. Plasma
  188. Plasma Clouds
  189. Polar cap absorption (PCA)
  190. Practical Applications
  191. Predict skywave propagation now
  192. Predicted Sunspot Numbers
  193. Predicting Propagation
  194. Propagation Conditions
  195. Propagation DX
  196. Propagation forecast
  197. Propagation modes
  198. Proton Flux
  199. Propagation | modes of HF radio propagation
  200. Propagation Forecast
  201. Propagation of Radio Waves explained
  202. Propagation Prediction
  203. Propagation Prediction Programs and Forecasts
  204. Proton Flux (Pf)
  205. PSK Reporter
  206. PSKR - PSK Reporter
  207. R1-R5 Radio Blackouts
  208. Radio Amateur
  209. Quick Guide to HF Propagation Using Solar Indices
  210. Radio Blackout conditions
  211. Radio Propagation - Free Software
  212. Radio Propagation Forecasting
  213. Radio Propagation Online Tools
  214. Radio Propagation Software
  215. Radio Propagation Tool
  216. Radio wave propagation in the ionosphere
  217. Radio Waves
  218. Radio Waves Propagation
  219. RBN - Reverse Beacon Network
  220. Real Time Activity of Radio Amateurs
  221. Real-time Data
  222. Real Time DX Propagation Conditions
  223. Real Time HF Propagation map
  224. Real-Time HF Propagation Prediction
  225. Real-Time MUF and Solar Indices
  226. Recent Geophysical & Solar Observations
  227. Recent MUF distribution
  228. Recent Observations - Geo (Terrestrial) & Solar
  229. Regional Conditions
  230. Regional HF Conditions
  231. Regional MUF and Solar Indices
  232. Remote sensing of the ionosphere
  233. S1-S5 Solar Radiation storms
  234. SDO - Solar Dynamic Obervatory (NASA)
  235. SDR - Software Designed Radio
  236. SDR Spectrum
  237. Seasonal variations in HF radio propagation
  238. SFI - Solar Flux Index
  239. Short Wave
  240. Skip distance
  241. Skip zone
  242. Skywave
  243. Sky Wave Propagation
  244. Software for HF Propagation Prediction
  245. Solar Conditions affect HF Radio Propagation
  246. Solar Cycle
  247. Solar Data
  248. Solar Events
  249. Solar Flares
  250. Solar Flux Index (SFI)
  251. Solar Indices
  252. Solar Observations
  253. Solar Phenomena
  254. Solar Radiation
  255. Solar Radio Flux
  256. Solar Spectra
  257. Solar Storms
  258. Solar Synoptic Map
  259. Solar Terminator (i.e. Greyline)
  260. Solar Wind
  261. Solar Wind Reports
  262. Solar X-Ray
  263. Solar X-Ray Flux levels
  264. Space Wave
  265. Space Weather
  266. Space Weather Events
  267. Space Weather Prediction Center (NOAA)
  268. SWPC - Space Weather Prediction Center (NOAA)
  269. Space Weather Scales
  270. Sporadic E
  271. Sudden Ionospheric Diaturbance (SID)
  272. Sunlight
  273. Sunspots
  274. Sunspot Cycle
  275. Sunspot Number (SSN)
  276. Surface wave propagation
  277. Surface wave
  278. Space Weather Prediction Center (NOAA)
  279. T Index Map
  280. TEC - Total Electron Content
  281. Terminator line
  282. Terrestrial Geomagnetic Indices
  283. Terrestrial Observations
  284. Thermosphere
  285. Total Electron Content
  286. Troposphere
  287. Twilight zone
  288. Ultraviolet
  289. Understanding Ham Bands Conditions Banner
  290. Understanding Ham Radio Propagation
  291. Understanding HF Propagation Numbers
  292. Understanding HF Radio Propagation
  293. Usable HF Frequencies
  294. Using HF Beacon Tracking Programs
  295. Variations in HF radio propagation
  296. Vertical polarization
  297. Very High Frequency (VHF)
  298. Very Low Frequency (VLF)
  299. VHF Propagation Map
  300. View HF Bands Conditions at a glance
  301. VOACAP
  302. Wave Propagation
  303. What are Band Conditions Banners?
  304. What are the Solar Indices?
  305. What are radio waves?
  306. What are the current HF propagation conditions?
  307. What are the Geomagnetic Indices?
  308. What are the modes of HF Radio Propagation?
  309. What are the modes of Radio Propagation?
  310. What are HF band conditions?
  311. What factors influence HF Radio Propagation?
  312. What is Earth's magnetic field?
  313. What is Earth's Magnetosphere?
  314. What is Greyline propagation?
  315. What is Hale cycle?
  316. What is HF Radio Propagation Prediction?
  317. What is HF Radio Propagation?
  318. What is HF Wave Propagation?
  319. What is Ionization?
  320. What is NVIS?
  321. What is Plasma?
  322. What is Radio Propagation?
  323. What is Solar Activity?
  324. What is Solar cycle?
  325. What is Solar Wind?
  326. What is Space Weather?
  327. What is the current HF propagation?
  328. What is the difference between earth's magnetosphere and earth's magnetic field?
  329. What is the difference between the Greyline and the Solar Terminator?
  330. What is the difference between Global versus Regional HF propgation conditions?
  331. What is Total Electron Content? TEC
  332. Wide-Band WebSDR
  333. Why is HF used for long range communication?
  334. World Wide Space Weather Agencies & Services
  335. WSPR - Weak Signal Propagation Reporter
  336. WSPR Live
  337. WSPR Rocks
  338. WSPRnet
  339. X-ray bursts > Blackouts
  340. X-Ray Flux levels
  341. X-Ray flares
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