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The propagation of radio signals in the medium frequency band (MF: 300kHz-3MHz), the high frequency band (HF: 3MHz-30MHz) and even the very high frequency band (VHF: 30MHz-300MHz) is largely influenced by the condition of our sun and, through the emissions of our sun, also the earth magnatic field that captures these. Because of its importance for certain radio communications, a number of observatories continuously monitor the condition of the sun and the geomagnetic field. Follow the steps outlined on this page to get an instant view on how propagation conditions are right now. If you are completely new to the topic of shortwave propagation, then have a look at AE4RV's HF Radio Propagation Primer (Flash movie!).

Step 1: Collect Real-Time Solar-Geophysical Data

Sunspots	Sunspots & Coronal Holes	Coronal Holes
SIDC Belgium	DXLC Norway & SOHO	SpaceWeather & SOHO
Solar Flux		Geomagnetic Field
N3KL		N3KL

In general, the augmented electromagnetical solar flux originating from sunspots has a positive effect on HF propagation by improving the ionisation of the ionosphere and thereby increasing the maximum useable frequency (MUF) of the ionospheric layers, as well as their hop distance.

However, sunspots may exhibit a propensity to produce giant solar flares, staying for minutes to hours. The X-rays and particles originating from these flares are capable of causing sudden shortwave radio fadeouts on sunlit paths due to increased D-layer absorption starting at the lower bands and moving up with flare intensity. In the case of an or an be sure to monitor the absorption curve on SEC's D-region absorption chart. During quiet episodes of solar activity, this graph will remain void.

Next update in minute(s). SEC

In an other, slightly more delayed mechanism, particles escaping from the Sun's coronal holes or freed during coronal mass ejections travel at high speed through space along the Sun's interplanetary magnetic field. This is called the solar wind. If these particles get trapped by the Earth's geomagnetic field they cause aurora upon entering the Earth's atmosphere at the magnetic poles. The effect is more pronounced when the z-component of the interplanetary magnetic filed B_z is pointing south relative to the Earth's magnetic poles (see leftmost dial). Geomagnetic disturbances , reflected in higher A- and K-indices, might bring good DX to the VHF enthusiasts among us, but will have detrimental effects for propagation starting at the lower bands (≤10MHz).

An explanation for the experts: The Earth's magnetic field causes the ionosphere to become anisotropic. Hence, incident plane waves entering the ionosphere will split in an ordinary and an extraordinary wave. Upon exiting the ionosphere, both modes would normally recombine into a single plane wave, if it were not for the polarisation changes caused by the geomagnetic disturbances. This results in signal loss. The effect is called Faraday rotation.

Every day, the DX Listeners Club of Norway produces an excellent forecast and description of recent solar events, relating these to the measured values of solar flux and geomagnetical indices. If you want to find out how last week's solar and geomagnetic activity was affecting propagation conditions on HF, then read Tad Cook's, K7RA, weekly solar report (updated on Fridays). His report also includes a forecast. An overview of the current solar and geomagnetical condition is presented below.

The first step towards some serious real-time HF propagation forecasting is collecting the solar-geophysical data of the moment (i.e. solar flux and geomagnetic planetary A- & K-indices) from the Latest Geophysical Alert Message - WWV Broadcast printed in the white frame below.

This information is automatically refreshed every 10 minutes past the hour. Next update in minute(s). Make sure your PC's clock is accurate with Atomic Clock Sync.

Sunspot Number Progression 10.7cm Radio Flux Progression Planetary Ap Index Progression

You are eager to learn more about the terms that are used in solar-geophysical reports?
If you are in a hurry, have a quick look at this Glossary of Solar Terrestrial Terms of the .

For those who have more time to read, David A. Rosenthal upon request by Radio Netherlands, has compiled a very instructive and more comprehensive primer for helping us to understand solar-geophysical alert broadcasts. See below.

The Solar Guide - 3rd Edition Preface Geophysical Alert Broadcasts The Broadcasts Explained (1) The Broadcasts Explained (2) Further Information

by David A. Rosenthal (Radio Netherlands)

Step 2: Introduce the Solar-Geophysical Data into K1TTT's Java Applet

David Robbins, K1TTT, did a wonderful job writing a java applet for on-line Maximum and Lowest Operational Frequency (MOF and LOF) prediction (see below inset for definitions). Click here for K1TTT's detailed account of the program's development history.

Note: In order to run java applets in your browser, you will need to install Sun's Java software. Once downloaded, close all browser windows during installation. If after installation, you only see a little "java cup" in a grey field instead of the applet, then go to Start > Settings > Control Panel > Java Plug-in > Proxies, configure the proxy settings and apply changes. Previously, a similar Virtual Machine (VM) was shipped by default with Microsoft's IExplorer. However, in consequence of a legal dispute, Microsoft is no longer permitted to ship nor support its VM.

Simply point and click on your QTH on the map, introduce the values for solar flux and geomagnetic A-index & K-index you obtained in Step 1 and, if necessary, convert the time to UTC. Select Polar QTH and hit the Compute button.

IF YOU ARE SEEING THIS TEXT YOUR BROWSER EITHER CAN'T OR WON'T SHOW YOU THE JAVA APPLET. CHECK YOUR CONFIGURATION TO BE SURE YOU HAVE JAVA ENABLED IF YOU THINK YOU SHOULD BE SEEING IT. THIS IS JAVA NOT JAVASCRIPT SO IT MAY NOT WORK WITH 16 BIT OPERATING SYSTEMS.

Legend: MOF LOF 10m 160m 15m 80m 20m 40m SP: Short Path LP: Long Path LP = SP + 180°

Reminder: Basic MUF(3000)F2 is the Maximum Useable Frequency for a 3000km single hop refraction off the F2-layer with a probability of about 50%. The value of basic MUF is independent of antenna gain, transmitted power, emission class or required information rate. MOF (LOF) is the Maximum (Lowest) Operational Frequency that will allow tropospheric radiocommunications with a probability of 90%. As a rule of thumb, MOF = 0.85 MUF. foF2 (not shown on this page) is the maximum (or critical) ordinary mode radiowave frequency capable of perpendicular reflection from the F2-region of the ionosphere.

Alternative to Step 1 & 2:
Have a Look at a Real-Time Basic MUF(3000)F2 Forecast Map

provides us with this great world-wide basic MUF(3000)F2 map.

Click on the map to learn more about its interpretation.

This image is automatically refreshed every 5 minutes. Next update in minute(s). Make sure your PC's clock is accurate with Atomic Clock Sync.

For those living in Europe, a real-time European basic MUF(3000)F2 forecast map for the next hour, based on real-time ionosphere soundings has been reproduced below, by courtesy of , the Radio Communications Research Unit. Visit their website for more and future forecasts.

This image is automatically refreshed every minute past the hour. Next update in minute(s). Make sure your PC's clock is accurate with Atomic Clock Sync.

Monthly Propagation Charts

If you are living in Europe and not far from Belgium, you may also be interested in these monthly propagation charts of the UBA.

The ARRL provides a similar product for US amateurs here.

Alternative to Step 1 & 2:
Connect to a DX Cluster

Perhaps the most straight-forward manner to get know current on-air activity, is to connect to a DX cluster, like the DX-Summit WebCluster, maintained in Finland by OH9W. Antonio Pernas, EA1CSI of Radioaficion.com made a really nice control window for this cluster. With his permission, an adapted and translated version in English is presented below.

The main advantages of above web cluster are the user-friendly spot filters and the fact that the connection never times out. A disadvantage is that you will see DX spots from DX spotters from all over the world! Therefore, to determain whether certain decametric bands are "open" at your QTH, it might be a better idea to acces your nearest DX cluster which you can locate with the help of The DX Cluster Telnet Directory. Type the command SH/DX to see the most recently spotted DX stations.

You can also obtain solar-geophysical data from your local DX cluster. For example, my nearest DX cluster is ON0DXK-5, located in Kortrijk, Belgium. After opening the telnet session, login with your call sign. Use the commands SH/WCY or SH/WWV to obtain the latest solar-geophysical reports. The result should be similar to this:

ON4BAA de ON0DXK-5 26-Dec-2001 1556Z > sh/wcy Date Hour SFI A K Exp.K R SA GMF Aurora Logger 26-Dec-2001 15 259 7 2 1 246 act qui no <DK0WCY>

Note: If in Windows, HyperTerminal starts instead of the standard black telnet application, open a Windows Explorer window (not Internet Explorer) and go to Tools > Folder Options > File Types. Select extension N/A with file type URL:Telnet Protocol. Click on Advanced, then select Open and click on Edit. Change application used to perform action to: rundll32.exe url.dll, TelnetProtocolHandler %1 Click twice on OK and then Close. Note: Launching HyperTerminal would reset these changes.

Step 3: At Dusk or Dawn, Point your Antenna along the Grey Line

The grey line (US: gray line), also called twilight zone or terminator, is a contour band around our globe that separates the sunlit portion from nocturnal darkness. These zones of dusk and dawn are somwhat diffused regions since the Earth's atmosphere tends to scatter the light into the darker areas. Furthermore, there are some time delays involved with the ionisation and de-ionisation of the ionosphere by sunlight.

Propagation of the lower shortwave frequencies (upto about 10MHz) is more efficient along the grey line then at other times. The reason is that the D-layer, which absorbs HF signals below 10MHz, dissappears rapidly after sunset and needs time to build up after sunrise, while the other, refractive layers E, F1 and F2 are still, respectively already, ionised.

It is important to note that, except at the equinoxes (21 March & 21 September), the grey-line direction will be different at sunrise from sunset, meaning different areas of the world can be contacted in the evening from those in the morning. Over the span of a year, the grey-line direction will vary 23° either direction, reaching this maximum tilt on the 21 June and 21 December, respectively.

In order to deal with this complexity, a tool like the GlobeView java applet, designed Chris Bruns, proves to be indispensable. Chris, a cartography expert, was even so kind to apply a few changes to his applet in order to render it even more useful to us radio-amateurs.

The grey line tool will be at its most useful when you select the Azimuthal Equidistant projection as indicated below. In this projection, the direction of the grey line coincides with the necessary antenna heading.

Note: In order to run java applets in your browser, you will need to install Sun's Java software. Once downloaded, close all browser windows during installation. If after installation, you only see a little "java cup" in a grey field instead of the applet, then go to Start > Settings > Control Panel > Java Plug-in > Proxies, configure the proxy settings and apply changes. Previously, a similar Virtual Machine (VM) was shipped by default with Microsoft's IExplorer. However, in consequence of a legal dispute, Microsoft is no longer permitted to ship nor support its VM.

Step 4: Call CQ «Seek You» according to your Regional Bandplan

When calling CQ «Seek You», make sure to be calling on the right calling frequencies! Furthermore, one should adhere to one's regional IARU (International Amateur Radio Union) bandplan.

Click either left image for viewing, or below link for printing the IARU Region 1 HF bandplan (PDF 318kB).  Region 1

Also available for downloading: US amateur bandplan (PDF 49kB).  Region 2

(PDF 128kB)  Region 3

Or Shout into a Contest

Find out when, on what frequency and in which mode by visiting this great contest service site:

Step 5: Who am I talking to? - QSL Info

Step 6: Reap the Rewards immediately with eQSL

Optionally: Use Professional HF Propagation Prediction Code for Free!!!

In the opinion of many, VOACAP (Voice of America Coverage Analysis Program) is simply the best choice around when having to select a HF propagation prediction code. It simply takes so many more factors into account such as the required signal to noise (S/N) factor and the properties of the transmitter and receiver antennas. The good news is that you can download this marvelous piece of software for free! But before you head off, it is a good idea to read this excellent Propagation Theory and Software primer by Jim Coleman, KA6A. It explains very well how to use VOACAP and for those who have not made up their mind yet, many screenshots of VOACAP are shown.

Propagation Theory and Software Part I - Introduction Part II - VOACAP (IONCAP) Part III - CAPMAN Part IV - Contest Planning

by Jim Coleman, KA6A

You can also read what antenna-modelling guru Brian Beezley, K6STI has to say about VOACAP.
Brian is the author of the MININEC and Antenna Optimizer (AO) antenna-modelling software codes.

Here it is: Download HFWIN32 (Contains amongst other, similar programs, a 32-bit version of VOACAP for Windows-NT/2000 & 95/98/ME). Be careful: Unlike above applet, this program requires the current Smoothed Sunspot Number (SSN) as input, not the Solar Flux (SF). The current SSN can be obtained from this page. Most useful are the Signal-to-Noise Ratio (SNR) area plots. Make sure you understand and apply the fundamental relationship between signal bandwidth and required SNR normalised at 1Hz bandwidth. The latter is greater than the required SNR at signal bandwidth. Alternatively, simply use the RECAREA program instead (also included with this download). In this program you can specify signal bandwidth directly. Bandwidth, bit rate and SNR at bandwidth are, in turn, related by Shannon's Theorem. Finally, review the gain of the sample antennas using the included HFant program. If necessary, modify the antennas.

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