HF Propagation Prediction Tool

LodeRunner sends the following guide to using the online propagation predictor tool. As most of you with HF experience likely know, the solar conditions have been quite a challenge as of late and will likely be so for a while to come. That said, regional and long haul HF communications are definitely possible even at low power levels provided one has a basic grasp of the way propagation works, how to wring the most efficiency out of their antenna arrays, and the best operating techniques for your intended purpose. One easy way to plan your regional communications is by using the HF Propagation Prediction tool.

On-Line Tools for HF Propagation Prediction

HF communications, and particularly NVIS communications on 160/80/40 Meters, are highly dependent upon conditions in the Earth’s ionosphere, which can change rapidly as a result of solar influences. Being able to predict the “Space Weather” is beyond the capability of most amateur radio operators. Thankfully, there are a number of on-line resources which reduce this to a few minutes work for you. Below I give a quick primmer on using one of the easiest on-line tools for this purpose.

Courtesy of the Australian government, you can run a fast and free Hourly Area Prediction (HAP) for your location and desired coverage area. The tool is located at:


You’ll need to select some starting parameters, as follows –

The location of your Base: Simple Click/drag on the map, or enter LAT/LON on the [BASE] tab of the page. The location of you ‘Base’ will be indicated on the map by a small triangle icon.

The Area you want to see the prediction for: Go to the [AREA] tab and enter a center LAT/LON and area size in degrees. Once you have entered these you may go back to the [MAP] tab and drag the selected (pink box) area if desired. The area you can run a prediction set for is limited – 20deg X 30deg works, and provides appropriate resolution for NVIS communications

Frequencies: go to the [FREQS] tab and click the [AMATEUR] button

Date and Conditions: go to the [DATE + T] tab and select the date on the calendar. If you’re running a prediction for tomorrow, then simply click on the [Northern Hemisphere] button to load the current atmospheric conditions for North America. If running a prediction for more than a day into the future, then a little ‘guessing’ is in order – The prediction tool uses what is called a “T-Index” instead of the more familiar SSN# (Smoothed Sunspot Number) so it’s not too difficult – setting the T-Index to 0 simply gives you their predicted value for that day. Positive numbers represent ionospheric enhancement above their predicted conditions, and negative numbers represent depressed ionospheric conditions (compared to their prediction).

Once you have made the selections above, then click the large blue [PREDICT] button in the upper right. Once you have done so, five new tabs will appear.

The [RESULTS] tab is in text format, and simply summarizes your input.

The [0-5UT], [6-11UT], [12-17UT], and [18-23UT] tabs are the charts for those hours in UTC (ZULU time), and look like this –





Reading these area predictions is simple. Simply look at the point on the map where the mobile/remote station is located, and the color of the map overlay at that location indicates the HF band with the best (predicted) conditions for making contact with that location from you Base location.

In this example, the Base is located in northeastern North Carolina. As you can see, the current NVIS conditions favor 80 Meters for communications during daylight hours, and 160M from 90 minutes after sunset [after 1900h/EST or 0000h/UTC] throughout the night, until about 30 minutes after sunrise 0800h/EST 1300h/UTC].

As we proceed towards the Solar Minimum, predicted to occur in 2019 or 2020, propagation will favor 160 Meters for NVIS communications to an increasing degree – near the Minimum, 160 Meters may be THE ONLY effective band for NVIS, 24 hour a day, for a year or more. For this reason I’ve prepared a forthcoming article on using a simple Inverted-L antenna for 160M and 80M NVIS communications.


22 thoughts on “HF Propagation Prediction Tool

  1. LodeRunner

    I should have mentioned in the article: these maps show propagation conditions only. You still need to provision the correct antennas to achieve your coverage requirements; but understanding which bands will best “get you there” in terms of propagation gives you a running start towards selecting and deploying the right antennas(s) to fulfill said requirements with a minimum of cost, time, and effort.

    Liked by 1 person

  2. Great tool. May even be better than the HF propagation tools I’ve used in the past because of its ability to set a target range for the contact. I find it interesting that 80m will have “gone long” at the time of the regional AmRRON nets. Makes me wonder if their SOI is going to have to be updated for conditions the next few years, making 160m their primary band in winter and 80m their summer band. I’ve noticed that the 7290 Traffic net is really struggling lately to support their primary customers (Texas). I’m running 20 watts halfway across the country and have to relay in almost anyone with 100w and a “5” in their call sign to net control, located in TX. My how the atmosphere is making things difficult for us this cycle. Time to go hang up that 160m dipole.

    Liked by 2 people

  3. Jon

    Thanks for this. As a newly minted general licensee I continue to learn the hard way. Very interested in your antenna articles. I am struggling to get a multiband HF wire antenna that actually works.

    Liked by 1 person

    1. Romeo


      In the same boat here….I have to be covert in my HF antenna at my shack due to HOA restrictions but have been able to make both DX/NVIS contacts using the aforementioned GV5R antenna mounted horizontally approx 20′ up…Also, a good antenna tuner like the ldg z-100plus is vital to insure a match to receiver..(just make sure you know how to tune it properly, as i needed a quick lesson, was doing it wrong i discovered)….

      I’ve also had decent results from an end fed unit, just 34′ in length, as a sloper or horizontal for NVIS..

      It is still magic to me, but thru trial and error, experimentation, you will learn what works for your rig, etc.

      Heck, i’ve even tuned up a gutter system…

      Hit a local club, go find a WFD event near you and just watch, ask questions, it will eventually gel.

      Obviously if you can make a class of BB’s, do it, soooo much knowledge to be gleaned….

      Good luck…

      ps… check these out: http://www.hamradiofun.com/yo-yo-vee-model4-6.htm

      Liked by 1 person

  4. Sorry to say, but a little more “Dick and Jane” instructions are needed to navigate thru the Aussie site and accomplish what the text above offers.

    I got to the Aussie site and eventually found the HAP site ( the exact steps were not given) — but after 30 minutes on the HAP page, I never did find a page that had “tabs” that you could use to enter the custom data.
    Perhaps someone could list ALL the steps necessary to get there.

    I’m not unfamiliar with this site as I have had one of their charts (MUF) listed as a favorite on my laptop, but the possibility of customizing it for my use was intriguing, so that’s why this article piqued my attention .
    Unfortunately I’m not a computer geek, so that’s why I pose this dumb request
    Thanks —

    Liked by 1 person

    1. LodeRunner

      bbrown – here’s a direct link


      Navigate to it by clicks, starting on the homepage at http://www.sws.bom.gov.au/
      Just click each link I’ve shown in [Brackets] as follows:
      [HF Systems] top center, under “Space Weather Services” Headline
      [Prediction Tools] in the Left Sidebar under “Online Tools”
      [HF Prediction] First item under “Tool” in the centered text frame
      /boom/ there you are – the default selection is “Hourly Area Prediction (HAP)”

      Once you arrive on the HAP page, if you’re not seeing the tabs across the upper edge of the map when you get to the HAP page, then there may be a setting in your browser that’s preventing the page from working properly.

      Try the above methods and let me know if you are able to tab through the [Map | Base | Area | Freq | Date & T ] portions of the page.

      Liked by 1 person

  5. LodeRunner

    Putting this tool (or any similar) in the perspective of a Scout unit; radio coverage forecasts such as these are an essential component for the Unit level S3 [Operations] to develop the SOI and Comms Windows which teams will take to the field.

    Not only is the coverage forecast essential to establishing usable operating frequencies and comms windows, it also allows the S3 to determine the optimum location for the deployment of the BRS (Base Radio Station) to support multiple teams in the field, while maintaining the lowest possible profile – in both the RF and physical environments.

    One of the key elements of using the forecast effectively is to select windows when the operating frequency will *just* support comms in the desired area, and not much farther. By careful selection of times and frequencies which employ such ‘boundary conditions’ to minimize propagational coverage to the minimum necessary area, the chance of intercept and/or Direction Finding (DFing) of Scout Teams and/or the BRS can be substantially reduced.

    In the example forecast above, there is a boundary condition between 2300hrsZ and 0000hrsZ for the 160 Meter band. Establishing a comms window from 2300~2345hrs and a [P]rimary frequency of 1855Khz, we obtain a minimized RF footprint while still supporting comms in our operational area.

    An effective [A]lternate frequency and window would be 80M between 2345 and 0030hrs, because 80M will support low-power NVIS operation during this window. However, the 80M alternate has a higher profile (much wider coverage area) than the 160M Primary frequency and window, so the risk of intercept is higher.

    If you have a good idea of where the opposing force’s Intercept/DF team is located, then this information can be used to refine the selection of frequencies & windows such that your area of operations is covered, but propagation to the opposing SIGINT facilities is absent, or at least substantially degraded.

    Remember this Rule of Thumb for NVIS paths –
    “Dawn denies to the East, Dusk denies to the West”
    That is, at dawn stations to your East will have degraded reception of your signals, and at Dusk stations to your west will have degraded reception of your signals.

    Liked by 1 person

    1. To add an additional context to this statement-

      We regularly used spaceweather.com to plan for HF conditions while planning PACE for a Detachment or Higher level operation. The Aussie tool is much easier.


      1. LodeRunner

        @ NCScout – “The Aussie tool is much easier. ”

        That’s why I chose the SWS on-line tool over VOACAP or Spaceweather,com

        Honestly, the best of the free tools is VOACAP – whether you use the online version or install it locally on your S6 (Commo Section) dedicated computer. When the ‘Net goes down, the online tools are gone, so I strongly encourage folks to do a local install of VOACAP and get used to running it.

        And your group should have a dedicated Commo system, which gets backed up regularly. Not just for the HF prediction tool(s) such as VOACAP, but also to house your SIGINT database, installable images of the software you use for Digital Modes, & etc.

        Here’s a link to the on-line version of VOACAP – http://www.voacap.com/p2p/

        Liked by 1 person

  6. Pingback: Brushbeater: HF Propagation Prediction Tool | Western Rifle Shooters Association

  7. Romeo

    If you run the app on a pc as a local instance, it has the states listed, then you can browse to a city you live in or near you and enter that as well for both tx and rx, it will do the rest…

    pretty nifty app….

    i’m running it on my win7pro box in office an plan to load onto field laptop as well…

    not alot of overhead/hardware requirements to make it function…

    Liked by 1 person

  8. LodeRunner;
    This site and what it does is AWESOME!

    As bbrown wrote, the site isn’t as intuitive as it could be however, I am smarter than the average bear and figured it out in less than 30 minutes thanks to your step-by-step instructions.

    I just posted your whole article on my forum for the hams there.


    Liked by 1 person

    1. LodeRunner

      @ Johnymac – Agreed. Even the “simple” propagation tools (and even ready-made charts) are confusing to most folks until they get some ‘elmering’ WRT what the inputs and outputs actually mean and how to use them. That’s why I prepared this write-up, and chose the simplest of the on-line customizable tools.

      At some point in the not-too-distant future, I plan to do a write-up on using VOACAP/ICECAP and methods of iterative analysis for – 1. Operational planning, and 2. as a Design Input for antenna modeling and optimization. It will be a —long— article, combining both the theory and practical implementation of multiple tools (VOACAP, NEC/EZNEC, etc.), so it will probably have to be done in 3 or 4 parts. I’ll discuss it with NCScout and we’ll figure out how best to get it on the calendar.

      73, LodeRunner

      Liked by 1 person

  9. LodeRunner

    Thank you for reading the comments and adding the step-by-step access instructions for computer dummies like me.
    I’ve since “played with it”, and also went into the VOACAP program that you mentioned (and downloaded the program to my laptop), and I better understand the value of each.

    You mentioned in an earlier post that you were considering authoring a future series of postings that carried these concepts farther. If you do, I would ask that you please consider that part of your approach does it from the perspective of a reader that is not heavy into computers, but is mainly interested in using it “as a tool”.

    I have had my ham license for over 50 years, and was a Signal Corp 1Lt in Vietnam, but my interest in ham radio has long been only that of being a “tool” in a adverse situation — not DXing, not contesting, not building exotic equipment, etc. It’s highly unlikely that I will be in the position of leading the commo activities of a “group” — it will be just trying to get connected with the widespread “family” in a grid down situation.
    And, with the recent changes in ham license requirements, I think its a reasonable assumption that a good portion of this “new blood” has become hams for the same reason.

    With that in mind, what I believe would be very helpful would be a way to quickly access selected program features — particularly charts like the “Circuit Reliability” and 24 Hr Prediction Wheel” — on a Tablet computer (like my Apple I-Pad 4) in a location where the Tablet is not connected to Wi-Fi or Cellular. (A laptop is too cumbersome in a situation where “light weight/low volume” is a needed characteristic).

    And in a “dreamers world” of desired program attributes, it would also be very helpful if the program would also address all frequencies from (say) 1.8 mhz to 15 mhz — not just the ham bands (I do realize interpolation is possible).
    Why ? — in a true “grid down SHTF situation, I would consider all frequencies open for possible use, not just the ham bands.

    Thanks again for your time and effort to make your expertise available to us readers. It IS appreciated.

    Liked by 1 person

    1. If you want a quick chart, there’s one on the sidebar as a reference. The Min and Max Use Frequency tells us our window of bands to use.

      In a ‘true SHTF event’ you need the experience to actually listen to the bands for propagation. It’s be a good guess the internet is out also, so you have to rely on experience. We do this by listening for where the actual traffic is coming from and then by beacons.

      And not only no but hell no, would you ever consider “all of the frequencies open for use”. This is not only wrong but its stupid.


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