Friday, June 20, 2014

Propagation Planning for IARU/WRTC 2014

If you are planning to participate in this year's IARU HF Championship contest or the WRTC 2014 contest, you might be interested to know that I have today expanded my VOACAP Propagation Planner site at

Besides running batch predictions from one TX site to all CQ Zones, it's now possible also to run batch predictions to ITU Zones (short path & long path) as well. There are one analysis tool (Win & Mac) and Excel Workbooks available to make the prediction data into more readable form.

Currently, more than 110 locations covering most of the ITU Zones are included.

The Propagation Planner gives you a good start for planning your operating strategy, especially if you run the predictions for two different sunspot numbers (SSN): 70 and 140. For low bands, use the W6ELProp software or use grayline maps for planning the best operating times.

For those who want to make predictions for WRTC 2014, use the following coordinates for the TX site: 42.29N, 71.57W.

Tuesday, June 3, 2014

New features at VOACAP Online

I have added a couple of new features (some of which are requested by users) at VOACAP Online, . The changes in the page can be seen in the screenshot below.

New sections at VOACAP Online: Propagation Params and Today's Sunrise/Sunset Times.
The Year/Month section has been moved below the Google Map.

Propagation Parameters

First, there is a new section labeled "Propagation Params", or parameters that may affect propagation. In this section you can have access to parameters which earlier were not user-adjustable.

1. Es, or setting the ionospheric sporadic E layer (Es) on and off. This may (or may not) prove useful during summer months when Es propagation conditions are quite common. Please note that the use of the Es layer is otherwise discouraged as the sporadic-E model was not fully tested during the development of VOACAP. Nevertheless, the effects of the sporadic-E layer are not totally excluded in VOACAP calculations although the layer is not set.

2. Model, or selecting the propagation model. Three choices are available here: Auto, Ducted, and Ray-hop.

  • The default "Auto" or automatic model refers to Method 30 in the VOACAP speak. It's a propagation model that chooses automatically either the ray-hop model or the ducted (forward scatter) model to predict the signal power. There is also a smoothing function for ranges of 7,000 km or greater.
  • The (forced) "Ducted" model refers to Method 21 in the VOACAP speak. Typically, this model is used for paths of 10,000 km or more. The Ducted model forces VOACAP to simulate the ducted or forward-scatter mechanisms that can prevail usually at distances having 3 or more hops. This model may produce unrealistic results at shorter distances where the ray-hops should occur.
  • The (forced) "Ray-hop" model refers to Method 22 in the VOACAP speak, typically used for all circuits less than 10,000 km. It's a model that contains multiple ionospheric reflections, and includes all of the ionospheric and earth bounce losses. This model may produce extremely pessimistic predictions at the distances beyond the third ionospheric hop where ducted/forward scatter mechanisms can occur.

3. SSN, or user-settable smoothed sunspot number. Here you can set a specific SSN (i.e. sunspot number) to be used for calculations. Note that VOACAP Online knows about the current smoothed sunspot numbers so it may be advisable not to set any value to the SSN field unless you wish to conduct propagation experiments. After you have entered a value in the SSN field, press the TAB key (instead of the ENTER key) to run a prediction.

4. Min. TOA, or setting the minimum takeoff or arrival angle for antennas at steps of 1 degree, starting from 0.1 degrees (the default), up to 5 degrees. My default value has always been 0.1 degrees due to practical reasons. However, in the VOACAP literature, a value of 3 degrees is commonly recommended, as it can be a common lowest angle for arriving skywave signals due to the roughness of the terrain. Also, 3 degrees may be a good choice if your antennas are not located in a flat, unobstructed area. And if you are using isotropic antennas, you should avoid huge amounts of antenna gain at angles below 3 degrees. You are encouraged to experiment between 0.1 and 3 degrees to see differences in predictions, using different antennas.

Sunrise and Sunset Times

The second new section is labeled as "Today's Sunrise/Sunset Times (UTC)". The label itself is pretty self-explanatory per se. In this section, the Sun's rise and set times are calculated at both the transmitter and the receiver coordinates. All times are UTC.

These calculations were originally inspired by Steve's (G0KYA) 12-year-old article about grayline propagation. In short, the best predictions for grayline propagation or trans-terminator enhancement on low bands can probably be achieved by a close examination of grayline maps. Some also swear by W6ELProp.

The abbreviation GND (for Ground) refers to sunrise and sunset at the sea level. The letter "D" refers to sunrise and sunset at the bottom of the ionospheric D region. Similarly, the letter "F" refers to sunrise and sunset in the ionospheric F region.

In the summer, if you place the TX or RX marker close to the Arctic Circle, you will see that "--:--" will appear in the D and F region fields. This simply means that sunrise and sunset times cannot be calculated for those regions (because the sun does not set/rise during the summer at high latitudes. Alternatively, in the winter, the sun may not rise/set.).

Thursday, May 22, 2014

New version of PropPlanner software released for Windows and Intel Macs

In 2012, I opened a web-based service at - VOACAP Propagation Planner ( This service provides VOACAP HF propagation predictions as numeric data, instead of fancy graphics. The reason is that the numeric data when filtered and processed properly offer more accurate HF predictions. And for this purpose you will need some extra software to help you. This is where my PropPlanner software for Windows and Intel Macs comes in. I also offer an Excel template which gives you CQ zone-specific summaries and thus helps create your own contest or DX operation plan.

As you know, making predictions boils down to making optimum use of the openings — being in the right place at the right time. So, the better predictions you have, the better basis for operating planning.

Nevertheless, we must remember that predictions are just that — predictions, not exact science. And in particular, due to the nature of VOACAP, you must visualize low-band openings with the help of grayline map software such as DX Atlas by Alex VE3NEA or GeoClock by Joe Ahlgren. VOACAP predictions are of less help there.

The resources needed for successfully running VOACAP Propagation Planner are as follows:
  1. Web site ( that calculates VOACAP predictions and outputs the result as numeric data, and
  2. Windows or Mac software called PropPlanner (together with an Excel template) that helps you work on the VOACAP prediction data on your own computer and make it more understandable.
The VOACAP Propagation Planner manual is available in PDF format.
Give it a go, and let me know what you think.

Thursday, May 1, 2014

Comparing VOACAP predictions - or are we?

Today, I happened to read KY6R's blog entry about VOACAP HF predictions for a path from FT4TA (Tromelin) to his QTH. Rich was comparing VOACAP Online predictions to those of Stu K6TU. Here they are:

Tromelin prediction by Stu K6TU
Tromelin prediction by VOACAP Online

To be frank, I don't know what to say after reading Rich's piece. Predictions are just predictions but, nevertheless, I felt he seemed to be convinced that Stu's VOACAP prediction is much superior to what VOACAP Online is able to produce in general, but especially on the low bands. It's of course a known fact that VOACAP cannot predict low-band long-distance propagation accurately. There are many factors involved, specifically that VOACAP does not recognize grayline propagation which will play a major role in this particular case.

But what puzzles me is this: are we actually comparing apples to apples? I believe Stu's HF prediction is not at all a pure VOACAP-generated prediction on all bands. It seems to be a mixture of VOACAP-based predictions - and something else. And that "something else" is notably visible on the low bands. It would be enlightening to know where Stu's low-band openings with the predicted signal strengths are actually coming from. Is he using a tuned-up version of VOACAP?

Please note that Stu's prediction strangely ignores a potential opening on 30 meters at 14-17 UTC, or on 40 meters at 15 UTC for that matter, both predicted by the latest officially released VOACAP. This is the time for grayline propagation, too.

I ran a comparison prediction (the same path Rich used) with VOACAP on my PC, using extremely powerful 17-dBi isotropic antennas on both ends. This was to see whether the online version of VOACAP agrees with the PC version (yes, it does), and to see whether VOACAP can predict an opening on 80M if extremely powerful antennas are used. No, it cannot.

The PC version was the latest version of the publicly available VOACAP software package. The above is the result for November 2014, SSN 85.

Sunday, March 9, 2014

VP8ADE, Antartica's only ham radio beacon heard in Finland

Today, 9 March 2014 at 1900 UTC, I had the pleasure of hearing the VP8ADE beacon on 28284.9 kHz (nominally 28285 kHz). VP8ADE is the only amateur radio beacon in Antarctica. The distance between VP8ADE and OH6BG is over 16,000 km.

Hearing is believing, so here is the recording of VP8ADE at my QTH in Vaasa, Finland.

This is also the first time my Skimmer Server logs this beacon. The first spot was already at 1820 UTC:

OH6BG  28284.9  VP8ADE   5 dB  9 wpm   2014-03-09 18:58:00
OH6BG  28284.9  VP8ADE   6 dB  9 wpm   2014-03-09 18:38:00
OH6BG  28284.9  VP8ADE   9 dB  9 wpm   2014-03-09 18:20:00

Tuesday, July 23, 2013

VOACAP Online Next Generation: User Manual

VOACAP Online has got a face-lift, and, on this occasion, I decided to write a brief User Manual for the service.


VOACAP Online is a web-based HF propagation prediction service which uses VOACAP (Voice of America Coverage Analysis Program) as its calculation engine.

Unlike the previous version, this new service requires that SVG (Scalable Vector Graphics) is supported in your web browser. The latest versions of Microsoft Internet Explorer, Mozilla Firefox, and Google Chrome are known to work. The earlier versions may not be supported. If you encounter problems with the page, please try first to upgrade your browser to the latest version available. If you think you have found a bug, please report it to

The web interface is divided into three parts:
  1. a Google Map for setting the transmitter (TX) and receiver (RX) site coordinates. The easiest way to set the coordinates is to drag the markers to appropriate locations on the map. Under the map, the distance from TX to RX is given in kilometers and miles, and the bearing in degrees from True North. If you need to zoom in or zoom out the map for better details, just scroll the mouse wheel up and down.
  2. a circular prediction chart which is divided into 24 hours and which shows all the amateur radio bands from 10 meters (28 MHz) to 80 meters (3.5 MHz). The prediction shows the probability for a QSO between the TX and RX site, illustrated as colors. The white and blue colors indicate poor probability whereas orange and red indicate good probability. The exact probabilities can be seen by hovering the mouse over the chart. The prediction details (UTC hour, band and probability (%)) will be shown in the centre of the chart.
  3. the input values for the prediction can be set in the area below the Google Map and the prediction chart. There are three sections:
    1. Date
    2. Transmitter Site, and
    3. Receiver Site.
The new circular 24-hour prediction chart, which is updated as soon as any of the input values (coordinates, power, antenna, year, month, etc.) changes.

The Date Section

In the Date section you can choose the year (currently 2013, 2014, 2015) and month. In this section, it is also possible to set a specific SSN or sunspot number to be used for calculations. Note that VOACAP Online knows about the current sunspot numbers so it is advisable not to set any value to the SSN field unless you are conducting some experiments. After you have entered a value in the SSN field, press the TAB key (instead of the ENTER key) to run a prediction which is shown in the prediction chart.

Press the "This month" button to quickly re-set to the current year and month.

The Transmitter Site

In the Transmitter Site section you can, besides dragging the red marker to the appropriate location on the map,  choose the location from a list of DXCC countries. Basically, you use the Name field for entering a label for the TX site. But you can also enter the Maidenhead grid locator in the Name field, and press the "Loc calc" key: the corresponding coordinates will automatically be calculated from the grid locator and entered in the Latitude and Longitude fields. The latitude and longitude values can also be entered manually. When you do that, please press the TAB key to run the prediction.

In this section, you can also select the most appropriate antenna for the TX site. At the moment, only one antenna can be chosen for all amateur bands. The default is a dipole at the height of 10 meters (33 ft) above the ground. All TX and RX antennas are artificial in the sense that they are omnidirectional, which allows the user to see all possible openings to all parts of the world. In dipole-type of antennas, the height of the antenna is related to the elevation angle and the number of elements to the gain. When you choose an antenna, you should think about the elevation angles and gain, rather than the physical structure of the antenna.

In the TX power, you can select powers from 1 watt to 1500 watts at the given steps. 100 W is the default selection. Some line loss is assumed so that the actual power used in the calculation is 80% of the chosen power. In the TX mode, you can choose from CW, SSB and AM. CW is the default selection.

There are also two special settings: the setting of Es (sporadic E) layer to on or off. The default setting is OFF (No Es). This can be set to ON (Es) during the summer time when the effects of the sporadic E layer are strongest. The second is the setting of Short-Path or Long-Path. Short-path means the shortest distance between the TX and RX, and this so-called great circle path is visualized with a red line on the Google Map. If you set this to Long-path, you will go from TX to RX in the opposite way: the longest great-circle path.

Last but not the least, there are three buttons:
  • Swap TX-RX,
  • Set Home, and
  • Unset Home.
If you click on the Swap TX-RX button, the TX and RX locations will be swapped: the current TX location becomes the RX location, and the RX location becomes the TX location. You can accomplish the same effect by double-clicking the red (TX) or blue (RX) marker on the map. In this way, you will see that the circuits are not always 100% reciprocal. In VOACAP calculations, this is mostly due to the different level of noise power in the RX site.

By clicking on the Set Home button the TX Name, Latitude and Longitude will be stored in a cookie, to be used by your browser automatically when you visit VOACAP Online next time. If you press the Unset Home button, the cookie will be deleted from your browser.

The Receiver Site

In this section, the input options are similar to those of the Transmitter Site. The RX location can be selected from the pre-defined DXCC list, or coordinates can be entered manually in the Latitude and Longitude fields. If you enter the values manually, please remember to press the TAB key.

The Name field is used to give a label for this site, or alternatively you can enter a Maidenhead grid locator in this field and press the "Loc calc" button, and the latitude and longitude values will be calculated automatically.

Also the receiving antenna selection is exactly the same as for the Transmitter Site.

Below the Receiver Site section there is the "Run prediction!" button. This will calculate the detailed propagation prediction graph for the entire frequency range from 2 MHz to 30 MHz, and show the day/night times for each location. This was the only way of getting the prediction in the previous version of VOACAP Online.

That's it ... in a nutshell! If you have questions, please don't hesitate to drop me a note.

Thursday, May 16, 2013

VOACAP Online upgraded!

The online point-to-point HF (3-30 MHz) propagation prediction service VOACAP Online was upgraded this week. The Google Maps portion of the site is now using the API version 3, and some new functionality was added, too.

Perhaps it's a good time to take a more in-depth look at how VOACAP Online works. Consider the following a brief user's manual...

Google Maps for coordinate entry

Easy coordinate entry for the Transmitter (TX) and Receiver (RX) was one of the single most important design features at VOACAP Online. The stand-alone PC version of VOACAP does not offer it, and, in fact, not many others do, either. Choosing Google Maps for this purpose lowered the threshold of using VOACAP considerably.

On the initial map, there are two markers - red and blue - placed on the equator line in Africa. The red marker signifies the transmitter's location and the blue marker is the receive location. Perhaps typically, the transmitter is your QTH and the blue one is the DX station.

Need an easy start? Just drag the markers on the map to the desired locations. Zoom the map in/out with the mouse wheel and fine-tune the markers by dragging them to their exact positions. Then press the "Run the prediction" button. That's it!

Great-circle paths: short-path and long-path
There is always a red line between the red and blue markers, showing, by default, the great-cirle path (short-path) between the two locations. A long-path line can be shown when you choose "Long-path" from the pop-up menu by the "Specials" label. Drawing a long-path line on the map was earlier (in Google Maps API v2) not such a trivial thing. At that time, I received enormous help from Sami OH2BFO who programmed the required code. Now, in Google Maps API v3, there was a much simpler way to do it. Thanks Sami for pointing that out!

Distance and bearing

One of the new features is the on-the-fly calculation of the distance between TX and RX, and the bearing from TX to RX in degrees calculated from True North. The details can be found under the map (see image below).

Image 1. Distance and bearing.

And if you would like to swap the TX and RX locations, there are two ways to do it. The easiest way is to double-click on either of the markers. The bearing value will be re-calculated at once. You can also click on the "Swap TX-RX" button by the "Specials" label.

A closer look at the input values

The second most important design feature for VOACAP Online is that, after setting the TX and RX locations, all the input values have been pre-set as appropriately as possible so that you do not necessarily have to adjust them. You can simply press the "Run the prediction" button.

However, there are, of course, many cases where you need more control. Let's take a look at the input values (see image 2 below).

Image 2. The input pane on the right-hand side of the Google Maps.
There are three sections in the input pane: Date, Transmitter Site, and Receiver Site.

Date & Month, and SSN
The year and month values are automatically selected (by the Javascript code on the page) to reflect the current year and the current month. If not or if you would like to change them, just choose the desired year and month from the pop-up menus. At the moment, the selection of years goes to the year 2015. I regularly (manually) update the contents of this pop-up menu.

The SSN (or, Smoothed Sunspot Number) input field is a new feature which has been requested by many users. Now the user can enter any value between 1 and 200. Use integer values only. Please note that you can simply leave this field empty, and let VOACAP choose the correct SSN values.

At this point, I would like to take a few moments to discuss the pros and cons of this feature. By default, VOACAP Online does internally know the current SSN to be used for all the months of the years available. You can ask how can that be as the sunspot number varies day by day? The simple answer is that VOACAP does not operate on daily SSN figures but smoothed monthly SSN figures which are being predicted for many years ahead and which are re-adjusted at regular intervals.

The predicted SSN figures are based on the Lincoln-McNish smoothing function, and they are maintained by the National Geophysical Data Center (NOAA/NGDC). These are the sunspot numbers used in the database reduction for the worldwide ionospheric maps used in IONCAP and now VOACAP. This is why only these figures should be used with with VOACAP. Read George Lane's discussion on the sunspot numbers for VOACAP use.

However, there have been months in the past where the conditions have been well above the average for a couple of months, and a re-adjustment of SSNs would have been appropriate. Now this power has been given to the user. Just remember that, strictly theoretically speaking, entering a daily SSN value in the SSN field does not generally give you better (or more precise) predictions as VOACAP is not suited to real-time predictions at all. Read more about the theoretical background of VOACAP in my Quick Guide.

Transmitter Site
This section contains the input parameters for the Transmitter Site (the red marker on the map). The QTH pop-up menu features 481 locations around the world, including all DXCC entities. When you choose a location from this list, its name and the coordinates (latitude and longitude) will automatically be entered in their corresponding fields below. Much care has been taken to find the exact coordinates of even the smallest of the islands! If you happen to find a location with wrong coordinates, drop me a note!

You can also set the coordinates by entering a Maidenhead grid locator in the "Name" field and then pressing the "Loc calc" (or, Locator Calculator) button. The corresponding coordinates will be calculated and shown in their respective fields, and the TX marker will be set to those coordinates on the map.

Please note that while you are dragging any of the markers, the coordinates (latitude and longitude) will be calculated on the fly. When you release the mouse to place the marker at one particular point on the map, its Maidenhead grid locator will be calculated and shown in the "Name" field. This applies to both the TX and RX markers.

There is a huge collection of pre-calculated antennas to choose from. Choose the antenna that is the closest match to your particular antenna. All available antennas are tailor-made for VOACAP Online purposes: they are all omni-directional so there is no need to set the bearing to the RX location.

Then choose the transmitting power and mode. You can also experiment by adding the Sporadic E ionospheric layer to the picture by selecting "Es" from the pop-up menu to the right of the "TX mode" label. The default value is "No Es". However, especially during the summer, choosing "Es" takes the effect of the Es layer into consideration, explaining many of the short-skip contacts on higher HF bands.

Moving on. We already explained earlier the meaning of swapping TX and RX coordinates, and the choice of short-path and long-path great-circle lines on the map.

The last item in the Transmitter Site section is "Current point" with two buttons: "Set Home" and "Unset Home". If you click on the "Set Home" button, a cookie will be stored in your browser which contains the coordinates and the name of the current Transmitter site. This site will be the default start location when you use VOACAP Online next time (instead of the default coordinates of 0,0). If you want to clear the Home coordinates, just press the "Unset Home" button, and all VOACAP-related cookies will be deleted.

Receiver Site
The input parameters for the receive site (the blue marker) are much fewer but similar to those found in the Transmitter Site section. You can choose a QTH from the pop-up menu, or enter a Maidenhead grid locator in the "Name" field and press "Loc calc", or move the RX marker with the mouse on the map to the desired location. Then just select the receiving antenna.

Everything is now set so press the "Run the prediction" button. After a few seconds you will see the propagation prediction as a graphic. I will explain in a separate blog entry how to interpret the results and how to access the prediction data as text, too!