I always seem to find the coolest stuff when I’m looking for something else! While researching for a future Off Grid Ham article I happened across two on line propagation calculators that can determine what HF bands are best for any time or operating condition. There are many other similar calculators, but these are especially well done and highly recommended.
The Voice of America Coverage Analysis Program (VOACAP) was developed by the VOA to predict propagation paths and frequencies for VOA broadcasts. This algorithm would be useful to hams too, if only someone would put together a civilian version and offer it on line for anyone to use.
Click here to access the VOACAP calculator.
Well, that “someone” has come forward. All you need to do is enter data for the transmitter and receiver on the main entry page. They offer numerous choices for the TX and RX QTH in a drop down window, or you can drag-and-drop points on the world map. From there it will produce a graph with a curve for each ham band and how well it will work between the two entered points. VOACAP is capable of numerous different calculations, but the one that means the most to hams is “circuit reliability”. This factor tells you how likely it is you will be able to make a contact, expressed as a percentage. The x axis (horizontal) is the UTC time. The y axis (vertical) is the percentage.
The example below is for a path between Florida, USA and eastern Africa. It tells me that on 15 meters (the pink line) I have a 77% chance of making a contact at 1900 UTC.
The VOACAP propagation calculator will also take into account the type of TX and RX antenna, TX power, and noise levels. All these variables are easily entered:
You can produce charts predicting propagation out into the future. I’m not sure how accurate the predictions are, but if the government uses them, they are probably good. This is ideal for preppers and survivalists who have concerns about not having internet access in a SHTF scenario. All you need to do is prepare a chart going out a week, a month, or however long you feel you’ll need the data, then print hard copies and save them. You’ll have to run updates periodically to keep the charts fresh.
There is a well written user guide linked from the main page. You will need it to use all the other built in features. VOACAP is complex and has a learning curve but the amount of data one can get is breathtaking. There is more in VOCAP than you’ll probably ever need. This is a very powerful tool.
Proppy HF Circuit Prediction.
In another moment of serendipity I came across the Proppy calculator. This little gem is not as complex and will not go into as much detail as VOACAP, nor does it have nearly the depth of features, but it’s super-simple to use and will produce the most common data hams want.
As with VOACAP, you can either drag and drop your desired QTHs anywhere on the world map or enter coordinates manually. Then, enter the appropriate operating parameters in the System field. From there Proppy does it a little differently than VOACAP. The x axis is UTC time and the y axis is frequency. The color coded fields on the graph indicate the likelihood (as a percentage) of contact.
In the example below, I ran a chart for a coast-to-coast transmission across the USA. It’s a little hard to see on the screenshot, but my best odds for a successful contact are between 0200 and 1200 UTC on the lower HF bands (40, 80, 160 meters):
Proppy also has a very handy feature that will generate prediction charts a month out and present them in a downloadable .pdf file. This is one aspect where Proppy is better than VOACAP. Survivalists/Preppers can simply create a new chart every thirty days and save it on a flash drive, or print them directly. Proppy also has a well written manual but the features are so intuitive you may not need it. You can even prepare a chart to up to 12 other locations at the same time, which is great if you’re organizing a net.
What you need to know.
Having real data is always better than guessing. These calculators will help you determine a communications path to any point in the world, any time of the day. And if conditions are not good enough to make contact, you’ll know that too so you won’t be wasting your time and electrical power. For preppers/survivalists, this is invaluable data for contacting distant stations on a preplanned schedule. DXers, & contesters can see how a band’s effectiveness goes up and down over time. Both of these websites are worth a bookmark.
Fabulous. Proppy looks excellent. Thanks!!!!
I’m glad I could help. I think you’ll be very happy with the results.
That’s neat. I have to admit I’d never heard of any of these. They’re going to make useful tools when I’m looking to try to make contacts in specific parts of the world. My favorite is Psk Reporter at https://pskreporter.info/pskmap.html You can plug in a specific mode of communication such as SSB, CW, PSK, etc, a specific band, and a time period; the last hour, two hours, ten hours, etc. and it will show who is monitoring what, from where, all over the world. I use it by plugging in my call sign so I can see where my signal is reaching when I’m operating.
Propagation is a fascinating thing. I’ve made contacts on bands that were supposedly “dead” and apparently had no radio traffic at all by calling CQ just for the heck of it. One morning I couldn’t sleep and was up around 4 AM local time, turned on the rig for the heck of it, and ended up working Australia with 40 watts and an antenna that was little more than a wire strung up in the back yard at 8 feet off the ground.
Anyway, thanks a lot for the information. These calculators are going to be very useful.
Hi Randall, as your experience suggests, it’s not always a good idea to go by what some algorithm says. Sometimes, just taking a shot in the dark produces very pleasant results. Still, as I mention in my article, data is better than guessing. Hopefully these calculators will come in useful when you can’t rely on your wits.
First time I’ve seen these. Thanks for links
You’re most welcome, Robbie. Thanks for stopping by Off Grid Ham.
Chris the VOACAP package is also downloadable. I did not run it, but it will probably will NOT require internet access to run on one’s PC.
Hi Greek, I was not aware that VOACAP had a download version. Thanks for passing the tip along.
Chris and Fellow HAMS:
This is my experience with several excellent propagation programs. Internet access is not available at my rural QTH. Satellite works well in the ad copy but not the real world. I do however, have power line RFI at times so it is not paradise.
All propagation programs are based on statistical models for a given month. The program will tell you that a path is open X% of the time that month, and the best times. Hint: even if the chance is low get on the air and call CQ. It may be your lucky day. Have made several All Time New One’s when the odds were not in my favor.
Based on my experience, there is not a lot of difference in the output of the three programs listed below.
Bear in mind that I’m not a hard core DX’er or contester. I frequently mentor new and not so new HAMS and these are my propagation software recommendations in order of complexity and features.
W6EL. One of my favorites as it is simple, thorough, and easy to use. I’ve had no problems running it on any version of WIN from WIN 2K to WIN 7 (32 or 64 bit) including WIN 7 Pro. The only very minor glitch is that it may or may not properly display the Great Circle map depending on your version of WIN 7. If I was lucky enough to be stranded on a desert island with food, water, etc, and my radio, vertical, PC, and just one propagation program, this is the one I’d use.
VOAPROP by G4ILO. This is a ‘front end’ for VOACAP. It requires installing VOACAP but not using it directly. This also works well on WIN 2K – WIN 7.
VOACAP. This is the Gold Standard that our tax dollars paid for. It can be downloaded directly. Since links change as often as the weather a web search will locate it. An excellent site for VOACAP information is: http://www.voacap.com (good link as of 4/6/18). There is a lot of information regarding the on-line and stand alone versions of VOACAP there. For the stand alone version I suggest reading and studying the VOACAP Quick Guide and Overview. It works well on WIN 2K – WIN 7.
The program takes some time to learn but the effort is worth it.
K9LA has written tutorials for W6EL and VOACAP. They’re well worth downloading and reading.
73 & Good DX
Hi Lew. For starters, thank you very much for your detailed reply and the insights you provided. The extra information offered by readers like you goes a long way in advancing the hobby and is a big part of what makes amateur radio so great.
Every article on Off Grid Ham is carefully researched but there will always be something missed. And even if I did have all the information available on a topic, I’d have to leave a lot out to keep articles from running too long. There’s just too much out there to possibly cover it all so having readers patch up the holes is greatly appreciated.
Thanks again for your contribution and I hope you’ll stop by Off Grid Ham again soon.
Hi Chris. I haven’t really looked into any of these propagation forecasting tools, so I welcome the information. I’ll brush up on ‘propagation,’ and check out Proppy initially. Given my poor hearing, any advantage (ie. better propagation) will be well-worth it! Maybe I can do a demo at Field Day this June 23-24. Even if only a few folks are interested, it would be worthwhile! Thanks for all the info!!
Hello Mike, Off Grid Ham is mainly focused on alternative energy for amateur radio. Propagation isn’t particular to off grid power, but anything I can do to advance the hobby in general is worth doing. That’s why I occasionally drift away from the main focus of this website.
I strongly suggest you follow through with your Field Day demo. You’ll learn something yourself even if the audience is not large. I know you are relatively new to ham radio and it’s gratifying to see you making an effort to pass knowledge to others. You don’t have to be an expert on everything to be helpful to others.
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