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Welcome to the HF Panel, a resource to study the propagation status in the HF bands, with applications to radio communications. Please choose an option:
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Current Space Weather
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| Interplanetary Magnetic Field (IMF) and Solar Ionosphere Potential | |||
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Current space weather. Source: Rice University
Last data of solar activity and geomagnetism. Source: SIDC
Table of Contents
Ionosphere Status |
MUF & foF2 |
Space Weather |
Magnetosphere |
Absorption |
Aurora |
Grey Line |
Optimal Frequencies |
Bulletins |
Links |
Notes |
User's Manual (ES) |
HF Glossary (ES) |
HF Central |
EA4FSI Home |
Contact |
Ionosphere Status
Information about the grade of ionization in the ionosphere, showing total electron content (TEC) maps.
Grade of Ionization - TEC Maps 
The Total Electron Content (TEC) gives an idea about the ionization grade of the ionosphere. Its unit of measurement is the TECU (1 TECU = 10E+16 electrons per square meter). The zones with the highest TEC indicate the occurence of different ionization phenomena, such as photoionization, absorption, etc.
Wold Total Electron Content (TEC) Map - Updated every 60 min. Source: IPS (IRI-90 ionospheric model)
European maps of Total Electron Content (TEC): Current and last 24 hours - Updated every 60 min. Source: IPS (IRI-90 ionospheric model)
The maps are colored by total electron content. Warmest colors indicate higher TEC values, i.e. within regions of direct solar incidence (photoionization).
Access to the TEC global map - Updated every 5 min. Source: Jet Propulsion Laboratory (JPL)
Evolution of the TEC over Europe during the last day - Updated every 24 hours. Source: Deutsches Zentrum fuer Luft (DZL)
The maps are colored by total electron content. Warmest colors indicate higher TEC values, i.e. within regions of direct solar incidence (photoionization). As a general rule, the F2 layer cut frequency (foF2) will be higher with a great TEC. This way, those maps can give an idea of the hours of the day in which the foF2 is expected to be low or high. The DZL maps are derived from measurements of the L1 carrier of the GPS.
Real-time MUF and foF2
Measurements of the F2 layer cutoff frequency (foF2), used in NVIS communications. Variations of foF2 due to geomagnetic activity. Maximum usable frequency (MUF) computation for given paths.
Ionograms - Latest data
If the radio wave reaches the ionosphere following a vertical o near vertical path (NVIS), reflection will occur in the F2 layer only if the working frequency is below a threshold known as F2 layer critical or cut frequency (foF2), which can be measured using ionosondes. Two inonosondes provide public data in Spain: The Ebro Observatory (Roquetes, Tarragona, NE) and the National Institute for Aerospace Technology (El Arenosillo, Huelva, SW). The corresponding latest ionograms are shown. If you look for data from other ionosondes around the world, please see the world map below.
Latest ionogram from the Roquetes Station (Tarragona, Spain) - Updated every 15 min. Source: Observatorio del Ebro.
Latest ionogram from the El Arenosillo Station (Huelva, Spain) - Updated every 1 hour. Source: INTA
The intepretation of all the data collected by an ionosonde is a quite difficult process. Frequency (MHz) is represented on the X-axis and the virtual height (km) on the Y-axis. If the ionosonde detects ionospheric reflection for a particular frequency, a point is drawn on the coordinates corresponding to that frequency and virtual height. On the left side we can find derived empiric data such as the measured critical frequency foF2 (MHz) and the standard MUF for radio links of 3000 km (MUF(D)). On the bottom side we can find an estimation of the MUF derived for different distances, very useful if your goal is to establish HF radio links from points near the ionosonde to other stations located at the indicated distances, using oblique paths.
Worldwide network of Lowell ionosondes. Source: Center for Atmospheric Research, University of Massachussets
foF2 - Latest data
If the radio wave reaches the ionosphere following a vertical o near vertical path (NVIS), reflection will occur in the F2 layer only if the working frequency is below a threshold known as F2 layer critical or cut frequency (foF2), which can be measured using ionosondes. The following experimental maps are built using data from ionosondes located in Australia, Japan, South Africa, Italy, Argentina and the United States.
Current foF2 - World Map - Updated every 1-hour intervals. Source: IPS
Current foF2 in Europe - Updated every 1-hour intervals. Source: IPS
Current foF2 in North America - Updated every 1-hour intervals. Source: IPS
Current foF2 in Australasia - Updated every 1-hour intervals. Source: IPS
Current foF2 in the Western Pacific - Updated every 1-hour intervals. Source: IPS
Each map shows an extrapolation of the foF2 derived for each region, using data from the nearest ionosondes. Those values can be used as MUF thresholds for NVIS (Near Vertical Incident Skywave) links, that is, using a very high elevation angle aerial system, reaching up to 500 km of distance.
MUF(3000) - Latest data
URSI defines the MUF as "the maximum frequency for inospheric transmission using an oblique path, for a given system". Using oblique paths, we will have a different MUF for each link distance. The following map offers MUF data for radio links larger than 3000 km.
Near-real-time MUF(3000) global map - Updated every 5 minutes. Source: Solar Terrestrial Dispatch.
Press here to know how to use this map.
foF2 variations due to geomagnetic activity
When the geomagnetic activity is high, as a consequence of solar storms started by solar flares or coronal mass ejections (CME), the F2 layer cut frequency foF2 may suffer important variations which could affect the HF radio links, both NVIS and long-distance. A solar storm may cause the ionosphere's grade of ionization to be increased (higher foF2 and MUFs) or diminished (lower foF2 and MUFs). The following graph from NASA's SWPC shows the F region critical frequency (foF2) scaling factor, to be applied to the foF2 mean value in real-time. This graph will give an idea of the influence of a solar storm over the foF2 and the MUFs, showing their tendency to increase or decrease. However, to get the exact value of foF2 in real-time, it is better to use the ionograms provided in this panel.
STORM Time Empirical Ionospheric Correction Model. Source: NASA Space Weather Prediction Center.
Online MUF Calculators
Free online software available on the Internet for MUF calculations using a variety of parameters.
- ESA/AMSAT - Ionosphere Project - MUF calculation for radio links.
- K1TTT MOF/LOF Propagation program.
Space Weather
Solar wind parameters, solar X-rays, energetic particle flare monitor, solar activity monitor, images of the Sun and sunspot numbers.
Solar Wind
The solar wind is made of electrically charged particles originated by solar flares, which are travelling at very high speed towards the Earth. Altough the magnetosphere works as a protecting shield, in the cases of very intense solar flares, part of this wind impacts on the upper ionosphere, affecting radiocommunications in the HF and satellite bandsF.
Last data from SWEPAM (Solar Wind Electron, Proton and Alpha Monitor). Source: NASA/NOAA - ACE spacecraft
Current solar wind data. Source: NOAA/SEC
Last 6 hours data of the following solar wind parameters: Temperature (ºK), speed (km/s), proton density (/cm3), angle of incidence of the Bz component (Phi, degrees) and Interplanetary Magnetic Field (Bt, Bz). Please take a look here for further information.
Accumulated data of solar wind during the last 2 days. Source: Maryland University - SOHO Spacecraft
Solar X-Ray Flux
The Earth is subject to the radiation coming from the Sun. Part of this radiation is ionizing and can excite the oxygen and hydrogen molecules in the ionosphere, causing them to oscillate. This oscillation may cause those molecules to be dissociated into two atoms or even those atoms to detach some of their electrons. The most ionizing radiations generated by the Sun are within the range of ultraviolet (UV, wavelength between 20-300 angstroms) and the X-Rays (wavelength between 8-20 angstroms). The electron density in the ionosphere increases, causing radio waves absorption in the HF bands, making communications difficult to establish. The following graph shows real-time data of ionizing radiation density flux in the X-Ray band, coming from the Sun and measured by the NASA GOES spacecrafts.
Current solar X-ray flux - Updated every 5 minutes. Source: NOAA/SEC - GOES Spacecraft
The graph shows real-time data of the ionizing radiation density flux (watts per square meter) in the X-Ray band, measured by the GOES10 and GOES11 spacecrafts. The rightmost scale shows the intensity of solar flares as a function of the measured radiation flux density: threshold A and B indicate normal flares. The C threshold is an indicator of a small solar flare, M is related to medium flares, X with big flares and over X indicates a so far unseen flare.
Energetic Particle Flare Monitor
Another way of measuring the impact of the solar wind on the Earth is counting its number of electromagnetically charged energetic particles (protons and electrons).
Energetic particles monitor - Data from the last 2 days. Source: Maryland University - SOHO spacecraft
The monitor shows the amount of energetic particles, according to the PM_Min formula. The solar wind with very high density or temperature can cause high values of PM_Min. However, it is considered that only values higher than 6000 are related to solar flares. In normal conditions (quiet solar wind), the values are under 100. During solar storms this value increases.
Electron and proton density cummulative data during the last 24 hours. Source: NOAA/SWPC - ACE spacecraft
The graphs show the measured proton and electron densities for each energeting range between 35 and 1900 MeV. All values increase during solar storms. ACE RTWS EPAM stands for "Advanced Composition Explorer Real Time Solar Wind Energetic Ions and Electrons".
Solar Activity Monitor
When a Solar Wind Flare (SWF) of sufficient intensity occurs, the solar wind will impact on a concrete region of the Earth within minutes or hours. This impact on the ionosphere causes its ionization to change and absorption increases on large segments of the HF bands, leading to fading and radio blackouts. The following map shows the solar wind impact regions in real-time and the Absorption Limited Frequency (ALF).
Current HF fading due to solar activity - Updated every 5 minutes. Source: IPS
The map shows the Absorption Limited Frequency (ALF), defined as the minimum frequency of a radio wave able to propagate over about 1500 km paths. Make an estimation of the first reflection point in the ionosphere in the working path and identify the ALF in the contour lines. If the frequency you pretend to use is lower than the ALF, it is very unlikely that your radio link could be established. If it is greater than the ALF, possibilities grow.
Images of the Sun
Images of the Sun taken by the SOHO Extreme Ultraviolet Imaging Telescope (EIT), at different wavelenghts. Solar Data Analysis Center, NASA Goddard Space Flight Center.
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Coronameter image from the Mauna Loa Solar Observatory (Hawaii). The coronameter offers a clear view of the solar flares generating solar wind at very high speed.
Current solar corona image. Source: Mauna Loa Solar Observatory
Sunspots
The sunspots are solar regions radiating approximately half the energy of the rest of regions in the solar surface. The higher number of sunspots, the higher grade of ionization, causing the MUF to increase and making easier to establish ionospheric reflection radiocommunications in the higher HF bands.
Current Michelson Doppler Imager (MDI) picture. Source: SOHO/NASA
The image shows the latest picture taken with the SOHO's MDI instrument, in which you can see the current sunspots and sunspot groups. During the solar cycle minimums the sunspot number is very small to the point that in some cases there are no sunspots at all. Every solar cycle can be identified by the magnetic polarity of their sunspots: for a given solar hemisphere (North or South), all the sunpots have the same polarity during the cycle. The sunspots in the other hemisphere will have the opposite polarity during the same cycle. Every 11 years, when one cycle finishes and the next one begins, the Sun flips its magnetic polarity and the orientation of the sunspots is also inverted.
Sunspot cycle - Updated once a month. Source: SIDC
The graphs show the sunspot number evolution during the last years. This number follows periodic cycles of an estimated duration of 11 years. On the cycle peaks the sunspot number is higher and the propagation conditions are better. Due to the fact that some sunspots may appear grouped, the "Wolf number" is used in the computation, which takes into account both the groups and the isolated sunspots.
Sunspot Numbers (ISN, SSN)
The sunspot number is necessary as a parameter for many HF propagation calculator programs. This number can be presented in a variety of formats.
Link to the NOAAA's National Geophysical Data Center (NGDC) pages, where you can get current data about the Sunspot Number in different formats, including ISN (International Sunspot Number, compiled by the Sunspot Index Data Center in Belgium), American Relative Sunspot Numbers, ancient sunspot data and Group Sunspot Numbers..
Note for VOACAP users: please use the Smoothed International Sunspot Number (SSN) via this direct link: Smoothed International Sunspot Number at NGDC
Magnetosphere Status
Real-time information about the interplanetary magnetic field (IMF) and the geomagnetic field (the Earth's magnetic field).
Interplanetary Magnetic Field (IMF)
The Interplanetary Magnetic Field (IMF) is the name of the magnetic field created by the Sun. Due to the solar rotation (one complete rotation every 27 terrestrial days), it has an spiral shape. The Earth creates its own magnetic field, which works a a shield against the solar wind. The region of the space in wich both magnetic fields interact is called magnetopause. If the IMF reaches the Earth following the southwards direction, it in part cancels the Earth's magnetic field, making easier for the solar wind to reach the ionosphere (solar storm).
Total IMF (Bt) - Updated every 2 min. Source: Solar Terrestrial Dispatch |
IMF on the 'z' axis (Bz) - Updated every 2 min. Source: Solar Terrestrial Dispatch |
The IMF is a vectorial field wich three dimensions named x, y, z, being the yz plane orthogonal to the plane of the ecliptic. Following this coordinate system, if the Bz component of the IMF is negative, the IMF points towards the South of the Earth anf if it is powerful enough can make easier for the solar storms to appear. The graphs show the total IMF (Bt) and the IMF along the 'z' axis (Bz).
Geomagnetic Field Perturbation (Kp)
The geomagnetic field (the Earth's magnetic field) is perturbed due to its interaction with the solar's magnetic field (IMF). Those perturbations can be measured using magnetometers, installed all along the Earth, wich offer the 'K indices' as a result of their measurements. The combination of the K indices measured by different magnetometers every 3 hours results in the 'Kp planetary index', which is represented in the following NOAAA graph.
Kp planetary index in the last 2 days and 1-day forecast - Updated every 15 minutes. Source: NOAA/SWPC
Please refer to the following table to know how to interpret the Kp values:
| Kp=0: Inactive geomagnetic field | Kp=5: Minor solar storm |
| Kp=1: Very quiet geomagnetic field | Kp=6: Moderate solar storm |
| Kp=2: Quiet geomagnetic field | Kp=7: Severe solar storm |
| Kp=3: Unsettled geomagnetic field | Kp=8: Very severe solar storm |
| Kp=4: Active geomagnetic field | Kp=9: Extremely severe solar storm |
Geomagnetic Field Perturbation (Ap)
Apart of the Kp index, the geomagnetic field perturbations can be measured also using a similar parameter known as Ap planetary index. The following graph shows the near-real-time Ap planetary index computed by the Australian Government IPS Radio and Space Services:
Ap planetary index in the last month - Updated every 24 hours. Source: IPS
Please refer to the following table to know how to interpret the Ap values:
| 0<Ap<30: Quiet geomagnetic field | 50<Ap<100: Major solar storm |
| 30<Ap<50: Minor solar storm | Ap>100: Severe solar storm |
Ionospheric Absorption
Absorption Limited Frequency (ALF) measurements, D-Layer absorption, per-band absorption maps.
Absorption Limited Frequency (ALF)
During a solar storm the ionization of the ionosphere's D layer increases, causing higher levels of absorption of the radio waves. This phenomena is called fading.
Current HF fading due to solar activity - Updated every 5 minutes. Source:IPS
The map shows the Absorption Limited Frequency (ALF), that is, the minimum frequency able to propagate along about 1500 km paths during absorption events. To interpret the map during one of those events, estimate the first reflection point in the ionosphere for the working path and identify the ALF using the contour lines. If the working frequency is lower than this estimated ALF, it is most probably that the radio link will not work. Using a working frequency higher than the ALF increases the probability of establising the radio link.
D-Layer Absorption Prediction
During a solar storm the ionization of the ionosphere's D layer increases, causing higher levels of absorption of the radio waves (fading).
"D" Region absorption due to solar activity - Maximum affected frequency. Source: NOAA/SEC
The D region is the lower region in the ionosphere and the radio waves suffer from absorption (never reflection) when crossing it. The higher the ionization degree in this region, the higher the absorption level. This is common during the daylight. In the images, all the frequencies under the "Maximum affected frequency" are subject to high absorption in the D Region. Absorption in this region rarely affects frequencies higher than 10 MHz.
Per-band Absorption Maps
During a solar storm the ionization of the ionosphere's D layer increases, causing higher levels of absorption of the radio waves (fading).
Absorption (dB) at 5 MHz - Updated every 5 minutes. Source: Solar Terrestrial Dispatch
Absorption (dB) at 10 MHz - Updated every 5 minutes. Source: Solar Terrestrial Dispatch
Absorption (dB) at 15 MHz - Updated every 5 minutes. Source: Solar Terrestrial Dispatch
Absorption (dB) at 20 MHz - Updated every 5 minutes. Source: Solar Terrestrial Dispatch
Absorption (dB) at 25 MHz - Updated every 5 minutes. Source: Solar Terrestrial Dispatch
Absorption (dB) at 30 MHz - Updated every 5 minutes. Source: Solar Terrestrial Dispatch
Each map shows the current absorption levels for the corresponding HF band (5, 10, 15, 20, 25 and 30 MHz).
Auroral Activity
Information about aurorae and their effect on HF radio communications: auroral oval and aurora forecasts.
Auroral oval
Aurorae borealis occur during episodes in which the interplanetary magnetic field (IMF) module is powerful enough and its Bz component points southwards when reaching the Earth, The solar wind reaches the polar areas and collides with the atoms and molecules of the upper layers of the atmosphere, causing the emission of radiation at different wavelengths (colors). Aurorae borealis activity causes the electric currents within the ionosphere to increase, making higher the probability of fading in the radio paths crossing the aurora due to absorption, especially in the 160 meters HF band.
Auroral oval in the North Pole. Source: NOAA/POES
Auroral oval in the South Pole. Source: NOAA/POES
Auroral oval in the North Pole - Updated every 5 minutes during significative activity conditions. Source: Canadian Space Science Data Portal - Red de magnetómetros CARISMA
Aurora Forecasts
Aurorae borealis occur during episodes in which the interplanetary magnetic field (IMF) module is powerful enough and its Bz component points southwards when reaching the Earth, The solar wind reaches the polar areas and collides with the atoms and molecules of the upper layers of the atmosphere, causing the emission of radiation at different wavelengths (colors). Aurorae borealis activity causes the electric currents within the ionosphere to increase, making higher the probability of fading in the radio paths crossing the aurora due to absorption, especially in the 160 meters HF band.
Visible auroral activity estimation - Updated every 1 hour. Source: Solar Terrestrial Dispatch
Latest aurora forecast. Source: Geophysical Institute, UAF
The maps show an estimation of the geographic locations with higher probability of aurora borealis occurrence.
Grey Line
Real time information about the current geographic ubication of the grey line.
Current Grey Line Plot
The grey line is the threshold between day and night. The D Region in the ionosphere (in which HF signals absorption occurs) quickly disappears in the dark side of the grey line, rising again in the opposite side. Propagation conditions are optimal in radio paths following the grey line.
Grey Line - Please reload the page to update the image. Source: F6KIM Webcluster
The current grey line position in the world map is shown.
Optimal Working Frequencies (OWF)
Real time spectrum monitors and information about the optimal frequencies to establish radio links in the HF bands.
Spectrum Monitors
Spectrum monitors analyze the intensity of the radio signals received all along the HF bands, showing the results in graphs. Those graphs can provide an idea of the better working frequencies for each hour of the day. The image shows the measurements from the HAARP site in Alaska (U.S.A.) during the last 36 hours in the 0-40 MHz segment.
HAARP project spectrum monitor (Alaska). Source: HAARP Project
For each time instant (horizontal axis) and each frequency (vertical axis), a brighter point indicates higher received signal intensity.
Optimal Working Frequencies Forecast
Current optimal working frequencies for global radio links. Reliable during 80% of time of the corresponding month, unless geomagnetic storms or solar flare events. Select the region in wich one of the sides of the link is located.
Optimal Working Frequencies in each geographic area. Source: Propagation Resource Center - NW7US (HFRadio.org)
Click on the region where one of the radio stations is located. A table will show the optimal working frequencies to establish a radio link with any of the other regions.
Conditions in the 160m band for medium and high latitude radio paths in the Northern Hemisphere. Source: Solar Terrestrial Dispatch
Bulletins
Bulletins and last minute information from several organizations worldwide, about the current solar activity status, the space weather and their impact on the radio and satellite communication systems.
National Atmospheric and Oceanic Administration
Latest bulletins from NOAA (USA):
NOAA/SWPC - Today's Space Weather.
NOAA/SWPC - 3-day Report of Solar and Geophysical Activity.
NOAA/SWPC - Space Weather Advisory Bulletins.
NOAA/USAF - Joint USAF/NOAA Solar and Geophysical Activity Summary.
NOAA/SWPC - Latest Solar-Geophysical Data.
NOAA/SWPC - Solar Cycle Progression.
NOAA/SWPC - Radio User's Page.
NOAA/NGDC (National Geophysical Data Center) - Solar Data Services.
NOAA/SWPC - Auroral Activity Extrapolated from NOAA POES.
NOAA/NWS - Space Weather for Aviation Service Providers.
Geophysical message alert, every 3 hours. Source: NOAA/NWS Space Environment Center
European Space Agency (ESA)
Latest bulletins from the European Space Agency (ESA):
ESA/AMSAT - Ionosphere Project - Per-band propagation predictor.
ESA/BAE Systems - Daily Ionospheric Forecasts Service (DIFs).
Rutherford Appleton Laboratory
Latest bulletins from the Rutherford Appleton Laboratory, radio communications research unit (UK):
RCRU/Rutherford Appleton Laboratory - Short-Term Ionospheric Forecasting (STIF).
Other interesting bulletins
SOLAR ACTIVITY:
NASA - Current images of the Sun.
Current geomagnetic storm level (Berkeley University).
USGS - National Geomagnetism Program - Real time geomagnetic data.
Lockheed-Martin: Latest solar events.
Solar activity report (Big Bear Observatory, New Jersey Institute of Technology).
AURORA:
STD - Hourly SDT DMSP/POLAR Auroral Activity Report.
HAARP (High Frequency Active Auroral Research Project) - Data Index.
SuperDARN - Real time global convection maps.
University of IOWA - VIS current images (POLAR spacecraft).
John Hopkins University - Latest auroral data.
GREY LINE:
PROPAGATION:
Monthly propagation forecast by EA3EPH (spanish).
THUNDERSTORMS:
AEMET (Agencia Estatal de Meteorología) - Latest lightning map in Spain.
Links
Links to forecast centers, research, education and others of interest about HF radio communications.
Forecast Centers
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European Space Agency (ESA) |
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Space Weather Prediction Center (SWPC) National Oceanic and Atmospheric Administration (NOAA, USA) |
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Rutherford Appleton Laboratory (United Kingdom) |
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Daily Ionospheric Forecast Service (DIFS) BAE Systems |
Research and Education
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COST 724 (Europe) |
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International Space Environment Services (ISES) Federations of Astronomical and Geophysical Data Analysis Services (FAGS) |
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NOAA National Geophysical Data Center National Oceanic and Atmospheric Administration (NOAA, USA) |
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National Space Weather Program Interagency program (USA) |
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Space Weather - The International Journal of Research and Applications American Geophysical Union (AGU, USA) |
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Space Science Institute (SSI, USA) |
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SWENET - Space Weather European Network European Space Agency (ESA) |
Civil Protection
General Directorate of Civil Protection and Emergencies (DGPCE, Spain).
Emergency Radio Network (REMER, Spain).
Amateur Radio
Spanish Government
National Frequency Plan (CNAF).
Notes
The goal of this page is to offer real-time interesting information for the Radio HF band users.
This is a non-official page.
All images displayed are property of their respective authors. The source is shown below every image.
Please check the date of publication of each image for validation purposes.
You can find a brief description of every image on the paragraphs marked as ""
You can find how to interpret the data on the paragraphs marked as ""
If you need further detailed information regarding each data, refer to the tutorial (in spanish) clicking "".
For any questions or comments, please contact me using this form.
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Page last updated: 29-Jul-2009.