radio propagation
here you can find a collection of many websites and resources related to radio propagation reports and predictions.
My first intention is to collect them but also to explain how to interprete data and terms. The focus is mainly on HF ionospheric radio propagation.
Introduction to HF radio propagation
added on 07-Jan-2021
The first step to understand how the HF radio waves propagate and the tools listed in the following articles is to have a clear idea about what is the ionosphere and what are the ionized layers involved in the radio waves reflection.
I found this educational page of SWS really useful and well made to explain the main concepts.
hamqsl.org
added on 03-Jan-2021
source: http://www.hamqsl.org/
This is probably the table that is widely known related to HF/VHF propagation prediction, it is not a static picture but a realtime status in your location???
The first column reports some “mysterious” numbers used to produce the more intuitive visual results in the second and third columns. Details of each table section can be found in the below tabs.
The fields related to the 80-10 m bands are quite intuitive (Good, Fair, Poor).
Geomag Field: indicates how quiet or active the earth’s magnetic field is based on the K-Index value. Reports as Inactive, Very Quite, Quiet, Unsettled, Active, Minor Storm, Major Storm, Severe Storm, or Extreme Storm. Higher indications can cause HF blackouts and auroral events. Updated every three hours.
Sig Noise Lvl: indicates how much noise (in S-units) is being generated by interaction between the solar wind and the geomagnetic activity. A more active and disturbed solar wind, the greater the noise. Updated every ½ hour.
MUF US Boulder: provides the maximum usable frequency in MHz at one of 11 locations worldwide. Updated every 15 minutes.
Solar Flare Prb: reports the probability (in %) of a solar flare within the next 24 hours (0-100%). Updated every hour.
Aurora: reports Band Closed for No/Low Auroral activity, High LAT AUR for Auroral activity >60°N, or MID LAT AUR for Auroral activity from 60° to 30°N. Updated every ½ hour.
EsEU/EsNA (sporadic E – Europe / North America): reports Band Closed, High MUF when 2M only is open, or 50/70/144MHz ES when the respective band is reported open. Updated every ½ hour.
EME Deg: Reports EME path attenuation as Very Poor (>5.5dB), Poor (4dB), Moderate (2.5dB), Good (1.5dB), Very Good (1dB), Excellent (<1dB). Updated every ½ hour.
MUF bar: provides the Maximum Usable Frequency in a colored bar. Gray indicates No Sporadic E (ES) activity , blue indicates ES reported @ 6M, green indicates ES reported @ 4M, yellow indicates conditions support 2M ES, and red indicates reported @ 2M. Updated every ½ hour.
MS bar: provides the Meteor Scatter activity in a colored bar. Gray indicates no activity. See the color coded graph at the bottom of the bar for activity level. Updated every 1/4 hour.
Impact on BANDS OPENING
SFI (Solar Flux Index): intensity of solar radiation measured at 2800MHz. Good indication of the F layer ionization (layer that gives us most of our DX on HF). The higher the number, the greater the level of ionization is, and the higher the frequency. Measured three times daily, and the last received value is reported.
304A: relative strength of total solar radiation at a wavelength of 304 angstroms, emitted primarily by ionized helium in the sun’s photosphere. Responsible for about half of all the ionization of the F layer in the ionosphere. 304A does correlate to SFI. Updated hourly.
SN (Spots Number): daily Sunspot Number provided by NOAA, it does loosely correlate to SFI. Updated once daily.
Below a correlation between SFI and A values and bands opening:
- 64-70 (SN=0-10) – bands above 40m unusable
- 70-90 (SN=10-35) – poor to fair conditions all bands up through 20m
- 90-120 (SN=35-70) – fair conditions all bands up through 15m
- 120-150 (SN=70-105) – fair to good conditions all bands up through 10m
- 150-200 (SN=105-160) – excellent conditions all bands up through 10m w/6m openings
- 200-300 (SN=160-250) – reliable communications all bands up through 6m
Impact on GEOMAGNETIC STORMS and SIGNAL NOISE LEVEL
A,K indexes: A-index provides an indication of the level for geomagnetic activity, K-index measures disturbances in the horizontal component of earth’s magnetic field. Both high indicate geomagnetic field is unstable, and HF signals are prone to sudden fades, and some paths may close while others open up abruptly and with little warning. High K index/Low A indicates a sudden, abrupt disturbance in the geomagnetic field, which can cause an intense but brief disruption in HF propagation, but can cause an auroral event. Updated once daily.
Aurora, Aur Lat: indicates how strong the F-Layer ionization is in the polar regions. Higher values cause auroral events (including northern/southern lights) to move to lower latitude. “Aur Lat” gives an estimation of the lowest latitude impacted by the auroral event. Updated every 15 minutes.
Bz component: strength and direction of the interplanetary magnetic field as impacted by solar activity. Positive is same direction as the earth’s magnetic field, and negative is the opposite magnetic polarity. Cancels out earth’s magnetic field when negative, which increases the impact of solar particles in the ionosphere. Updated hourly.
SW (Solar Wind): speed (km/s) of the charged particles as they pass earth. The higher the speed, the greater the pressure is exerted on the ionosphere. Values greater than 500 km/sec have impact on HF communications. Updated hourly.
- (K=0-2) (Aur=<5) (SW=200-400) (Bz=0-+50) – Inactive/Quiet. No impacts on HF. Aurora 67-62°. Noise S0-S2.
- (K=3-4) (Aur=6-7) (SW=200-400) (Bz=0-+50) – Unsettled/Active. Minor HF fade higher lats. Aurora 60-58°. Noise S2-S3.
- (K=5) (Aur=8) (SW=400-500) (Bz=0 -10) – HF fade higher lats. Aurora to 56°. Noise S4-S6.
- (K=6) (Aur=9) (SW=500-600) (Bz=-10 -20) – HF fade higher lats. Aurora to 55°. Noise S6-S9.
- (K=7) (Aur=10) (SW=600-700) (Bz=-20 -30) – HF intermittent. Aurora to 50°. Noise S9-S20. (K=8) (Aur=10+) (SW=700-800) (Bz=-30 -40) – HF sporadic. Aurora to 45°. Noise S20-S30.
- (K=9) (Aur=10++) (SW=>800) (Bz=-40 -50) – HF impossible. Aurora to 40°. Noise S30+.
Impact on RADIO BLACKOUTS
X-Ray: intensity of x-rays hitting the earth’s ionosphere, impacts primarily the D-layer (HF absorption). Updated eight times daily.
A1-B9 No/Small Flare – No or very minor impact to HF signal
C1 Moderate Flare – Low absorption of HF signals
M1 (2000 per cycle) – Occasional loss of radio contact on sunlit side
M5 (350 per cycle) – Limited HF blackout on sunlit side for tens of minutes
X1 (175 per cycle) – Wide area HF blackout for about an hour on sunlit side
X10 (8 per cycle) – HF blackout on most of sunlit side for 1 to 2 hours
X20 (1 per cycle) – Complete HF blackout on entire sunlit side lasting hours
Impact on SOLAR RADIATION STORMS
Elc Flx, Ptn Flx (Electron Flux, Proton Flux): Density of charged electrons and protons in the solar wind. The higher the numbers, the more the impact the ionosphere, primarily impacts the E-Layer of the ionosphere. Updated hourly.
sws.bom.gov.au
added on 03-Jan-2021
In the HF Systems section of the Australian Government Bureau of Meteorology you can find the Ionospheric Map.
This is a critical ionospheric frequency (foF2) map produced using automatically scaled ionogram profiles around the world. The map shows colour contours of foF2 in units of MHz.

Ionospheric Station of Rome - AIS INGV Ionosonde
added on 03-Jan-2021
My Country is Italy, so here I present the data available from the ionosonde located in Rome; the main results are the critical frequency (foF2), the maximum usable frequency (MUF) and the height of layers responsible of radio waves ionospheric reflection.
If you compare the foF2 frequency of the plot below and the value of the Australian Bureau of Meteorology from the map above you should find comparable results.
- Critical Frequency (f0F2)

- Maximum Usable Frequency (MUF)

Other interesting data that I found really useful are the daily plots of f0F2 and MUF of the last 6 days; these plots clearly indicate the ionization effect of the sun exposure during the day, both frequencies are higher in the central part of the days.
Below the plots of critical frequency (f0F2), the white line is a monthly median expected value:
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Below the plots of Maximum Usable Frequency (MUF):
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pskreporter.info - a direct way to check the real time propagation (of Your signals)
added on 07-Jan-2021
There is also a “direct” way to verify the radio propagation, in this case the realtime performance of your station.
The main concept is to send a beacon message (CW, WSPR, FT8, PSK31, RRTY, etc) that includes your callsign and check on pskreporter map how far your signal goes.There is nothing magic, it is achieved by gathering and organizing data of all the SDR receivers that are connected on internet.
- if you have a rig capable to automatically transmit a CW message you can send a message like this: CQ CQ CALLSIGN/B CALLSIGN/B at a speed of around 20WPM, this is the easiest way because you don’t need a PC;
- if you are a fan of FT8 you can send a WSPR beacon or directly a FT8 CQ message with WSJT software.
Here some tips to visualize just the information you need...
- if you want to check how far your transmitted signal is received select the “sent by” option (red circle), otherwise you’ll see also the station received by you (if you’re playing with WSPR/FT8 for example).
- to have a clean view of the map start by checking the “display options” like in my image example, the default map shows also the location of all the receivers and lead to confusing results.
- you can monitor several bands, they are showed in different colors.

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