Friday, July 24, 2015

Introducing VOACAP DX Charts

After I have now more or less finalized the VOACAP Propagation Planner service (...for now...), I decided to create a spin-off service that calculates short-path (SP) and long-path (LP) HF propagation predictions from the user's QTH to some of the upcoming DXpeditions.

I call this service 'VOACAP DX Charts', and the address is : . This service of course uses much of the same technology I created for the Propagation Planner such as:

  • interactive propagation charts that show the QSO probabilities and signal power (hover the mouse over the table cells to see the values)
  • graphical presentation of sunrise and sunset times to help predict low-band openings (hover the mouse over the 'TX' and 'RX' labels on the bottom left of the tables to see the exact sunrise and sunset times in UTC)

An example DX propagation chart.

I have deliberately kept the layout of the results page to a bare minimum to allow the user to copy the charts to word processing, and make them pretty for printing.

To use this service, the user only needs to know his/her Maidenhead grid locator and press the "Run!" button. If you do not know your grid locator, I have created an easier-than-the-easiest Google Map application to help you find your grid locator : . Just zoom into your location on the map, and your coordinates and grid locator are readily visible on the top part of the map.

For the predictions, I have assumed that, on 20M to 10M, the DX uses a 3-ele Yagi at 10 meters AGL, and on low-bands a 1/4 vertical over a good ground. On the user's side, a 3-ele Yagi at 20 meters AGL for 20M to 10M, and a 1/4 vertical over a good ground are assumed.The TX power used is 1.5 kW.

Currently, the following DXpeditions are included:

  • TI9/RA9USU, Cocos Isl (Jul 2015)
  • K6W, Wake Isl (Sep 2015)
  • TX3X, Chesterfield Isl (Oct 2015)
  • 3B9HA, Rodrigues Isl (Nov 2015)
  • 3C7GIA, Equatorial Guinea (Nov 2015)
  • VK9WA, Willis Isl (Nov 2015)
  • 3Y0F, Bouvet (Dec 2015/Jan 2016)
  • KH5, Palmyra (Jan 2016)
  • VP8SGI, South Georgia (Jan 2016)
  • VP8STI, South Sandwich (Jan 2016)
  • FT/J, Juan de Nova (Mar 2016)
  • VK0EK, Heard Isl (Mar/Apr 2016)

Please let me know if you find bugs, or want more DX sites to the list.

73 Jari OH6BG

Saturday, July 18, 2015

VOACAP Propagation Planner Revisited!

VOACAP Propagation Planner is a comprehensive planning tool for HF contesters and DXers. So far, the only problem has been that you really must be a dedicated enthusiast to run all the software required to maximize your efforts either in contests or DXpeditions. Now, things have changed: A new, more user-friendly version — 2.0 beta — is finally available!

Preparing and planning for any worldwide contest or DX expedition (or hunting a DX) require a thorough analysis of propagation predictions. The propagation predictions help you, so to speak, get a good grasp of the playing field, i.e. where to play and when. The predictions tell you when and on what bands the best openings are in the given direction at a suitable signal strength, so that the QSO rates can be maintained at their best; at what times it’s good to use those valuable long-path openings, and when to focus on working those hard-to-reach areas while the band opens elsewhere at the same time.

The new online version now does all heavy-lifting and number-crunching on the VOACAP server, and visualizes the results in two ways: by CQ or ITU Zones (short-path or long-path) and by band-specific zone charts (short-path or long-path, as you wish). Be warned that there are quite a number of charts to analyze but I am confident all your efforts will greatly be paid off. The tables can easily be copied to word-processing software if you wish to make them fit better on paper. I strongly recommend using the Google Chrome browser to browse the pages as I found that some of the mainstream browsers on some platforms have hard time printing (and even copying) table cells with a background color.

It all 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, 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 not so accurate there.

Here are some screenshots of the renewed service:

1. VOACAP Propagation Planner,

The home page of VOACAP Propagation Planner. Please note that you can enter your Maidenhead Grid Locator into the Name ("TX") field and press the "Loc calc" button. The program will calculate the latitude and longitude values respectively.

2. The Propagation Prediction Charts

The results can be viewed zone by zone from the TX site the user provided. The colors indicate the probability of making a QSO between the TX and the Zone in question.

A cropped example of zone-specific predictions.
The elements of the top row are as follows (from left): CQ/ITU zone number, Path from TX to zone, Short-path (SP) or Long-path (LP), month and year, followed by the distance (kilometers & miles) of the circuit, and the bearing (in degrees) from TX to RX.

Below each chart, the sunrise and sunset times for TX and RX locations have been calculated and visually presented as horizontal bars. The silver color denotes night-time and white day-time. The exact sunrise (SR) and sunset (SS) times (in UTC) will come up as you hover the mouse over the TX and RX label texts on the left column. Here, in this example, the TX is "enjoying" the polar night so the sun will not rise at all. The date used in the calculations is always the 15th day of the given month.

All charts are interactive: if you hover your mouse over table cells, you will see a pop-up text, indicating the (VOACAP's REL) probability in percents, and the (VOACAP's S DBW) signal power values in dBW. For instance, the signal power value of -164 can be considered to be on the verge of the noise in remote locations whereas -93 corresponds to S9 on the S meter. Read more about translating the signal power values (S DBW) into S-meter values here: .

The left-hand side column shows the Zone number and the location within the zone. Many zones are geographically wide so, in many cases, a number of locations have been chosen from that zone to give a fair picture of the propagation possibilities.

All colors - except grey - indicate QSO-making probabilities. White means 0%, blueish 10%, greenish 30-40%, yellowish 50-60%, yellow-orangeish 70-80% and orange-reddish 90%, and pure red 100%. The color of grey does not indicate any probability value. Instead, it shows that, although VOACAP does not predict any probability for that specific hour, some signal power has been predicted which may translate into workable conditions. So, in a sense, grey indicates "a grey area" where QSOs may be possible. Typically, these grey areas can mostly be found in low-band predictions charts.

Propagation predictions use a color scheme from white to red.

All predictions charts start at 01 hours UTC. You may ask, "Why not start at 00 UTC?". Well, it's a matter of taste. All VOACAP predictions span 60 minutes but not necessarily the way you may think. A prediction for 01 UTC does not span from 01:00 to 02:00 but, in fact, from 00:30 to 01:30 UTC! So, I decided, being inspired by the original makers of VOACAP, to start at 01 UTC and end at 24 UTC. Following the same logic, 24 UTC means a time frame of 23:30 to 00:30 UTC.

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