Dominican Society of Amateur Radio INC (SDRA)

HF Band Conditions

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Understanding the Condition Banner on HF Bands

The above Solar-Terrestrial Data graphic was created and produced by Paul Herrman, NØNBH, and I refer to it as the Band Conditions Banner. Many of us have seen this on websites, Facebook group pages, and even in magazines. But it occurs to me that most of us find much of the information presented in the banner above our heads. While not all of the information on the banner is immediately relevant, I'd like to take a few minutes to decipher the content, based on the names of the fields it presents, grouped here more by function than by appearance on the banner.

This article does not explain all the details of the band condition banner. For example, some versions of the banner show photographs of the solar surface through one filter or another, but I won't go into details. For the most part, I describe the left and right columns, plus part of the center column in the graphic above. You can download your own free banner from Paul's website.

Date and time

UTC The date and time shown represent the last time the banner was updated at the time your browser was last refreshed, in GMT (Greenwich Mean Time), which today is called UTC. So, in the banner above, the time equals November 24, 2018 at 8:36 p.m. MST.

SFI (70 = poor / 160 = good / 280 = fabulous)

Solar Flux Index (SFI) ( 62.5 to 300) is the amount of solar radio noise measured at 2800 MHz (10.7 cm) and is updated daily. The SFI gives us an idea of how well the ionospheric F-layer can support HF radio communications, and more especially on 20 to 10 meters. Numbers below 75 are quite poor, while those above 160 are very good.

SN (2 = poor / 90 = good / 220 = fabulous)

Sunspot Number, The SN (0 to 250) is a calculation that is approximately 10 times the number of sunspot groups we face + the number of individual sunspots we face, and is updated daily. The SN usually follows the SFI and provides another indicator of F-layer ionization.

304A (80 = poor / 150 = good / 240 = fabulous)

304 Angstroms The 304A (0 to unknown) is the relative intensity of total solar radiation in the UV (ultraviolet) range, which originates mainly from ionized helium in the Sun's photosphere and often follows the SFI value. The designation following the 304A value (@ EVE, @ SOHO, @ SEM) indicates the instrument used to take the measurement and the value is updated hourly.

A Plntry (4 = calm / 40 = minor storm / 80 = severe)

A, planetary The Ap index is the long-term daily average stability of the Earth's magnetic field; the subscript "P" stands for planetary, or averaged from various locations around the Earth. The value ranges from 0 to 400; any value greater than 100 indicates unfavorable conditions for radio propagation and is updated once a day.

K Plntry (1 = calm / 5 = minor storm / 7 = severe)

K, planetary The Kp index is the daily average of short-term stability of the Earth's magnetic field, the subscript "P" stands for planetary, or averaged from various locations around the Earth. The value ranges from 0 to 9, any value greater than 5 indicates unfavorable conditions for radio propagation and is updated once a day.

Geomag Field

Geomagnetic field Relative label of the Earth's magnetic field activity, reflecting the Kp index. Labels include INACTIVE, VR QUIET, QUIET, UNSETTLD, ACTIVE, MIN STORM, MAJ STORM, SEV STORM, and EX STORM, in order of disruptive impact on radio propagation, and is updated every three hours.

Bz (20 = good / 2 = ok / -2 = not ok / -20 = disruptive)

B sub Z Vector of interplanetary magnetic field (strength and direction) perpendicular to the plane of the Earth's orbit, where positive values enhance the Earth's magnetic field and negative values cancel it. Values range from 50 to -50, updated hourly.

X-RAY (A1.1 = good / C5.0 = moderate / X2.3 = severe)

X-rays X-ray emissions impact most strongly on the ionospheric D-layer, so the stronger the radiation, the lower the ability of radio waves to propagate by refraction of the ionospheric waves. The intensity of X-ray radiation incident on the atmosphere, ranging from A0.0 to X9.9, is defined by a class (A, B, C, M and X), followed by a logarithmic quantity (0.0 to 9.9). ) which defines the intensity within the class, updated eight times a day.

Ptn Flx (0.10 = good / 2.0 = moderate / 20.0 = heavy)

Proton flux Density of protons in the solar wind, so the higher the value, the greater the impact on the ionospheric E layer. Values range from 0 to unknown and are updated hourly.

Elc Flx (<1000 = poco impacto / >1000 = fuerte impacto)

Electron flux Electron density in the solar wind, so the higher the value, the greater the impact on the ionospheric E-layer. Values range from 0 to unknown and are updated hourly.


SW (100 = good / 500 = moderate / 700 = disruptive)

Solar wind Average solar wind particle velocity in km/s, with numbers above about 500 affecting HF communications. Values vary from 0 to 1000 and are updated hourly.

Aurora (1/n=1.99: weak... 6/n=0.8: moderate)

Posibilidad de Aurora Fuerza relativa en GW de la capa F ionosférica, que afecta a DX sobre regiones polares, de modo que cuanto más fuerte es la ionización, mayor es la probabilidad de que se produzcan auroras en latitudes más bajas. Si se completan, los valores oscilan entre 0 y 10++ (por encima del factor de normalización, de modo que n < 2,0 muestra una confianza alta y n > 2,0 muestra una confianza baja), actualizados cada 15 minutos.

Aur Lat (70 = weak / 60 = moderate / 50 = strong)

Latitude of Aurora Lowest estimated latitude impacted by an aurora, in degrees N latitude. Values range from 67.5 to 45.0 o No report, updated every 15 minutes.

VHF Conditions

The VHF Conditions column provides an idea of the preference for SSB operation, at frequencies between approximately 50 MHz and 150 MHz. With the exception of Auroral Activity, the status of each applicable band reports how well E-Esporadic (Es) conditions over the particular continent support the band, and Band Closed for low or no activity is updated every 30 minutes.

These reports do not mention anything about ducts, because tropospheric propagation by duct propagation is primarily a climatic effect and is not directly predictable by solar measurements.


Auroral Activity General report of current auroral activity, shown as AVERAGE LAT AUR to indicate widespread activity between 30 and 60 degrees N latitude, HIGH LAT AUR to indicate activity confined to greater than 60 degrees N latitude, and Closed Band to indicate little or no auroral activity, updated every 30 minutes.

6m EsEU

Activity of 6 meters, Es in Europa 50 MHz ES indicates that 6 meters are open for E's.

4m EsEU

4 meter activity, Es in Europe 70 MHz ES indicates that 4 meters are open for E's.

2m EsEU

2-meter activity, E's on Europe 144 MHz ES, indicates that 2 meters are open for E's or high MUF, to indicate that conditions support Es propagation on 2 meters.

2m EsNA

2 meter activity, Es over North America 144 MHz ES indicates that 2 meters are open for E's, or MUF high to indicate that conditions support 2 meter E's propagation.

HF Conditions

The HF Conditions column is often where people look first to get an idea of the general propagation conditions on the HF bands, and is self-explanatory. Each band pair is listed with a separate overall condition report for daytime and nighttime operation, such as Poor, Fair, and Good, compiled from other banner data. The subjective conclusions are based on the combined contributions of the solar flux index, sunspot number, 304A value, Ap index and Kp index. Overall, this is what the three reports mean:

  • Good: capable of communicating with distant stations (DX) via multiple hops
  • Acceptable: Able to communicate with stations in the country by a maximum of one or two hops.
  • Deficient: largely incapable of communicating via skywave propagation.


Earth-Moon-Earth degradation Measurement of the best attenuation of the Earth-Moon-Earth propagation path (moon bounce), displayed as Very poor (high attenuation), Poor, Fair (medium attenuation), Good and Excellent (low attenuation), updated every 30 minutes.


Maximum Usable Frequency, Es The MUF, relative to sporadic E (Es), is the highest frequency that can be reliably used for skywave communication using sporadic E propagation. In this column, the banner shows the MUF as a color bar for each VHF band: 6 m = blue, 4 m = green, 2 m EU = yellow, 2 m NA = red and gray for no activity, updated every 30 minutes. The SEASON BREAK label indicates that E-Sporadic is normally not active at this time of year.


Meteor Scatter The Meteor Scatter activity bar shows the relative meteor scattering activity for the times of day indicated in UTC, using the MIN...MAX color scale below it. The bar shows colors for active times and gray for non-active times, and is updated every 15 minutes.

Signal Noise Lvl (S0 = excellent / S4 = fair / S7 = horrible)

Signal noise level The signal noise level is a logarithmic measure (in 6 dB increments, as seen on an S-meter) of the noise generated as a result of the solar wind, compared to the background noise. The greater the disturbance in the solar wind, mainly due to interaction with the Earth's magnetic field, the higher the S-value, and it is updated every 30 minutes.

MUF US Boulder (14 = 20 to 10 no-go / 29 = 20 to 10 ok)

Maximum usable frequency From one of eleven locations worldwide, the highest frequency that can be reliably used for communication using skywave propagation. Normally displayed in MHz, but also shows NoRpt if no information is available and is updated every 15 minutes.

Solar Flare Prb

Solar flare probability A solar flare is a sudden burst of radiation, composed of electrons, ions and high-energy electromagnetic radiation, on the surface of the Sun. This enormous emission can reach the Earth and enhance ionization of the ionospheric D-layer, absorbing radio signals and disrupting HF communications. The probability of a solar surface flare gives you an idea of how much your HF communication could be disrupted by a solar storm in the next 24 hours, and the value is updated hourly.


Paul does a great job of explaining the various fields of his banner on his website,, so I've stolen some of his information to compile here. And since Paul is the author, he has given everyone permission to post his banner on their own web sites, as long as they do not remove or hide his name or web site address.

Now you can impress your amateur friends with your knowledge of the information presented in this banner. But perhaps more importantly, you can take a look at the information and get an idea of what to expect when you listen to the radio, hopefully the sky will be in your favor.


Article translated from Noji Ratzlaff, KNØJI, Utah Valley Amateur Radio Club

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