WSPR has so many uses. Part One of this two part series was very popular and clarified some of the easiest aspects of WSPR. Part Two (below) from Marty (KB4MG) continues with some additional and more sophisticated uses of this mode. Enjoy!

Part Two - WSPR, The Mode that Ensures You Are Getting Out!

In Part 1 of this article we looked at the practicality of using weak signals to help us evaluate our antennas’ performance. We showed how receivers all over the world are listening on specific WSPR frequencies for these signals, and how they get reported to a database for analysis.  Now, in the next use of WSPR we look at how we can use this to compare antennas. Is this practical and can we get good data from this process?

Comparing Antennas

We have to be a little cautious when we talk about comparing antennas. You have to have the right expectations and process for this to be meaningful. Consider the caveats of any comparison tests:

• Naturally, different types of antennas have different radiation patterns.
• Each location has a local terrain consideration contributing to radiation patterns if there is any significant physical separation.
• Differing antenna heights will change antenna radiation patterns.
• Vertical vs horizontal polarization; each has a different take-off angle.
• An unstable ionosphere during the test makes it subject to fast & slow fading which can distort the data (more on that later).
• On low bands (less than 10MHz) you must consider expected day/night changes in propagation in the F layers. Running your tests for 24 hours will show this effect.

There are different reasons we may want to compare antennas, but first and foremost we may just want to know which one is better. But, better for what? Different antennas can have differing applications. For example, an NVIS (near vertical incident skywave) has the effect of shorting your skip zone to be able to make contacts more local to your QTH. It does not make sense to compare antennas for different functions. Design your comparison to be meaningful to your use cases.

Your first thought may be to just run on one antenna for an hour or two and capture that data. Run the other antenna for a similar timeframe and capture that data. Manually compare the spots using the analysis tools on WSPR.rocks. I have done this method and found it somewhat useful. Because of the time frames when I did this experiment, I saw more DX on one of the antennas. This was mostly because of gray line propagation in the test period, so choose your time of day carefully. For WSPR, gray line propagation effects are especially important at 30 meters and below.

Also, when looking at the data I have also found that the ionosphere is constantly changing. You will see this in the signal strength (dB) values reported by the same WSPR station receiving you at different times. It is like the ocean waves that roll in at a steady pace until suddenly there is a much larger wave. This variance in the solar flux is normal, but can mess with your comparison data. My conclusion is that signal strength data taken at long intervals, like an hour, is not too useful unless you use an averaging method. Averaging of the results will smooth the data and make it better correlated. Using a curve fitting capability in a spreadsheet program can help smooth the data. This challenge makes the case for having a way to automatically switching antennas with the WSPR transmitter at small intervals.

What if you want to just compare two of your antennas? Ideally it would be great if the WSPR transmitter automatically switched between the two antennas at a prescribed shorter interval. The out of the box products do not do this. The only product that can do it today is the QRPLabs Ultimate3S, but only by adding externally controlled relays. They have an application note AN003 that describes the needed connections and setup.

Another possibility is beaconing the two antennas at the same time. That removes the variable of the frequent changing ionosphere. I have not tried this technique, but it seems promising. There is no issue with running two at the same time on different antennas. Though it is possible they would collide on the same frequency that would be rare. Most WSPR transmitters change frequencies randomly within the WSPR band, so the chance of collision is low.

How long do I need to run the comparison? Wait for a full 24-hour period between antenna tests before you compare the WSPR data. There is one rub. How will you know what antenna sent what signal? WSPR has a strict limit of 6 characters for callsign, so any suffix you would add is not encoded. There is no way to mark the data of one versus another. You need to know which report is from which antenna, so you must know what transmission intervals correspond to what antenna. You must know which interval corresponded to which antenna. Loading the data into a spreadsheet and separating it there is a possible solution.

WSPR.live has a WIP (work-in-process) view that will show a comparison between antennas. Our Figure above shows the experimental azimuth display for two antennas based on spots. It is unknown when this will be a complete work. Like all free software, there are rarely deadlines. Watch their site for further work and updates.

Validating Propagation

When Dr. Joe Taylor designed this mode, it was to validate propagation conditions. Thus, it is part of the software WSJT-x suite, distributed for free by Joe and his team. It runs on many platforms including Windows, Linux, and Mac.

Joe and team created a ‘tool’ that can help with understanding propagation on a band or set of bands, in real time. In the early stages there were very few receivers; this left it far from useful in comparison to today. Now we have about 1600 receivers active all the time and it’s become a reliable resource.

[DGJ Note: Marty and I would love to see more WSPR receivers worldwide. In a recent discussion with Harry at ZachTek, we agreed to review the ZachTek receiver which, when paired with a laptop, makes the process of putting in an inexpensive WSPR receiving station painless. This new device will be reviewed in a future Short Takes feature on T&E.]

The massive amount of data collected each two minutes of every day gives us a picture of what is happening with propagation. There are three main ways you can look at this data.

• Personalized Propagation
• Persistent WSPR Beacons
• World View of all WSPR activity

When we think of Personalized Propagation ("my station’s" view) we must consider that WSPR is only a measure of what is possible with extremely low signals and specialized encoding. When we look at where our WSPR signal was received, this is not a true indication of what is possible with other modes. We have to consider the signal to noise (SNR) of the received signal. Anything lower than -20dB would not be possible with any other mode. In fact, if below 0dB it would hard to make a SSB contact. CW is lot better, but even the best operators need a signal greater than -12dB to copy. When you look at your data, keep this in mind. However, using another digital mode like FT8 can be workable at -20dB.

Also, compare what you are seeing in WSPR with propagation prediction sites like VOACAP and Proppy. They use very sophisticated methods that consider space weather and current readings of the ionosphere to predict what you may expect on a particular band and mode combination. I have found that the predictions have good correlation with the data, with some differences due to noise at my location, my specific antenna and pattern, and the antenna of the receiving station. The first figure shows a propagation report from Proppy for the 40 meter band at about the time of the grayline. My WSPR spots did in fact show that I had propagation into Western Europe and Scandanavia.

The figure below shows my WSPR Spots in their geography, which compares nicely to what is predicted.

Persistent WSPR Beacons

Aren’t all WSPR transmitters beacons? Well, yes, but we typically don’t run them 100% of the time. There is, however, a network of WSPR Beacons run by volunteers throughout the world and these do operate all the time. As of the writing of this article there are 50 of them worldwide. You can report these on the WSPR.live site under Dashboards/WSPR Beacons.

These can be useful to see if a band, like 10 meters, is open. Pick the WSPR Beacons in your part of the world and look at the Spots/Hour. This will show when the beacons are reaching the most receivers, which is an indication of band conditions at times of the day.

Look on WSPR.rocks for a report page showing the top beacons as well as the top spotters. It's an always interesting report.

World View of WSPR Activity

As I mentioned previously, people throughout the world are running WSPR beacons. The majority of these are using them for the use cases I have described. This data can be valuable to anyone interested in what is happening worldwide. Knowing the history of Spots we can make some conclusions about propagation.

The WSPR.rocks site has a chart showing the World Overview of WSPR spots by band. You can look at data as far back as 120 days. Here is an example of what you can see by analyzing past data.

If we look at the chart below for the week of October 7, 2024 you will see an anomaly in the WSPR Spots data.  What happened? You are seeing the effects of a G4 Solar Storm from a Coronal Mass Ejection (CME) that was earth-directed. It was not a total radio blackout but indeed had a very substantial impact on our propagation for October 10- 11, 2024. (See the NOAA website for more info on this storm.) You will then notice that the 20-meter and 40-meter Spots increase dramatically as this storm passes. This gives us insight into the effects of Solar Weather and how it can impact our ability to operate our stations and make contacts.

Participating with WSPR

Certainly, anyone can run WSPR mode with your current rig or a dedicated WSPR transmitter. However, as Dave mentioned earlier, there is a need for more receiving stations to improve the quality of the data. Consider using your rig as a receiving station when you are not operating. Another possibility is to purchase an SDR Dongle or standalone SDR receiver and setup a station. In my shack I use an Airspy HF+ as my WSPR receiver and connect it to a Windows 11 cube computer. You will also need to route the audio from the SDR to WSJT-x for decoding and uploading. The way to do this is using a Virtual Audio Cable (VB-Audio.com) to make this connection.

My operating procedure is that I change bands manually every so often but stay primarily with 10, 20, and 40 meters. Set one up yourself and you will be amazed by how many stations you will receive.

Other Uses

There is an application for WSPR for tracking High Altitude Balloons(HAB’s). This is a popular activity by students and research teams for know where their balloons are traveling. Both QRP Labs and ZachTek have products for this use. This application uses an alternative protocol that sends location, altitude, and battery data in additional packets. Check out the tracking on amateur.sondehub.org. You will see what balloons are currently active.

Conclusions

We have covered the most popular use cases for WSPR and there are many more. Having a working knowledge of this mode may inspire you to do some experimenting of your own. I am amazed at the tools and data analysis that is available to anyone who wants to use it. The combination of WSPRnet, WSPR.rocks , and WSPR.live will give you enough data to help you draw your own conclusions about your antenna(s) and your station. Take advantage of what is there.

And, one more plug for you to consider being a receiving station as a service to your fellow hams . . . it will help to give us better data on coverage from our antennas.  Hope to see your WSPR on the air!

Marty Buehring, KB4MG

[DGJ Note: Thank you to Marty for his efforts again in this issue. If you have a topic to write about of general interest to the amateur radio community, please do not hesitate to contact Dave Jensen, W7DGJ, who would be happy to discuss getting it into the QRZ column. Our readership numbers are phenomenal. Once again, I remind hams that not everything can be covered effectively on YouTube and that reading is a key aspect of brain health and enjoyment for our amateur radio interests.]