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 : www.voacap.com/dx.html . 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.

Added April 28, 2017: 60 meters!

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 : www.voacap.com/qth.html . 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, www.voacap.com/planner.html



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: http://www.voacap.com/s-meter.html .

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.