Everyone has a bucket list, things that need to be done before we ever wake up on the wrong side of the grass. Many bucket list items are far more targeted than realistic. Very few of us who have “A Journey Into Space” on our lists will live to see this fulfilled. And even the more realistic destinations, like the trip to Antarctica, which has been on my list for ages, become increasingly unlikely as your circumstances change – my wife hates the cold.
Fortunately, instead of going to Antarctica alone – and what fun would that really be? – I recently got part of the satisfaction of world travel via amateur radio. The final episode of “The $ 50 Ham” was featured Weak signal digital modes using WSJT-X;; In this article I mentioned a little about the Weak Signal Propagation Reporter (WSPR). In this mode, I was able to test what can be done with very low-power transmissions and virtually visit six continents, including Antarctica and Sweden via Alaska.
Whisper in the noise
Ask a casual amateur radio operator what’s on their minds right now, and the chances are the answer is, “How are the bands doing right now?” This is an abbreviation for the current state of the ionosphere, which largely determines how well RF signals bounce off the various layers of charged particles that wrap around the planet. These layers shift and move in daily cycles, going through longer-term cycles of strengthening and weakening that depend on the cycles of magnetic activity on the sun.
Assessing the state of the ionosphere and figuring out which ribbons have a path to which points on the globe was something Hams had to do by turning the dial and listening for beacon stations. Beacons are stations that periodically send a low power signal from a fixed, known location. If you can hear the beacon, chances are good that you have a path of propagation between you and the general area of the beacon on that frequency.
Beacons are useful, but they have their limitations. They depend on the friendliness of strangers who provide resources for the operation and maintenance of the beacon station. Beacons are also subject to occasional maintenance outages. So if you don’t hear a beacon that you’re expecting, it doesn’t necessarily mean you don’t have a path between two points. But perhaps the most limiting aspect of traditional beacons is that they work on a pull model – you have to sit down at your radio and intentionally tune the beacon’s frequency and decode what you hear – beacons almost always use continuous wave (CW) mode with Morse -Code. On top of that, anything you learn about the available propagation paths stays as good as in your hut and beacons are of limited use.
WSPR signal by Louis Taber, CC BY-SA 4.0
With this in mind, Joe Taylor (K1JT) began work in 2008 on a digital mode that was specifically designed for exploring propagation paths. The protocol has been referred to as WSPR, which of course everyone pronounces as a “whisper,” which is indeed an apt name given their capabilities. WSPR is a digital mode that uses special digital signal processing algorithms to decode signals with a signal-to-noise ratio (SNR) of -28 dBm in a bandwidth of 2,500 Hz.
When transmitting, WSPR sends a compressed 50-bit message that encodes the station callsign, network location and transmission power. The message is modulated by frequency shift keying with a very low bit rate – less than 1.5 baud. This means that it takes almost two full minutes to send an entire message with error correction. The transmissions are synchronized by the WSPR software so that one second begins every even minute. Accurate time synchronization is therefore essential.
Spread made visual
As cool as the WSPR protocol is, the magic of WSPR comes from the “R” part of its name: reporting. This is where WSPR closes the loop that conventional beacons leave open, as the WSPR client software can be configured in such a way that all WSPR signals received and decoded by a station are logged in a central database. WSPRnet.org is where all reports are placed. The site contains a searchable database of all reported “spots” as well as a map showing the current contacts of many, many stations.
The map on WSPRnet is admittedly a bit choppy – it’s based on Google Maps, and an error dialog pops up every time you load a new view. While there are other visualizations, despite the problems, WSPRnet’s map is a great way to see what propagation paths are currently available to you.
For example, I just took a quick look at the 20m band and found that from my region I have solid routes to pretty much all of North America. More importantly, I have no routes to Europe or Asia and very little south to Central and South America. But if I look at what’s going on with trails on the east coast of the US, where the sun is setting, and which are actively reaching multiple stations in and just off the coast of Antarctica, I could have a path to the bottom of the planet as the sun is over I’m going down
Do my part
As I mentioned in my first article on weak signals, WSJT-X is currently running on a Raspberry Pi 4 that I developed for amateur radio use. WSJT-X has a built-in WSPR mode that allows you to easily switch between exploring possible propagation paths with WSPR and using that information to create actual QSOs using FT8 or any of the other supported modes.
The nice thing about using WSJT-X for WSPR work is that it’s basically completely automated. Depending on how you set it up, you can either be a dedicated WSPR receiving and reporting station or you can also send it.
Whenever I’m in the cabin / office, which is almost always the case, I’ve set up WSJT-X to broadcast on WSPR with a 20% duty cycle – that is, every fifth two-minute block is reserved too send. That way I can do my part for the WSPR card – my part of Northern Idaho generally doesn’t have many WSPR beacons. I think this is my way of meddling. Also, I occasionally get the bonus of snapping a cool contact, like the aforementioned hit on DP0GVN-1, a German research vessel that was parked off the coast of Antarctica that I hit with just five watts on the 30m band .
Sweden, via Alaska
As cool as it is to know that you’ve made solid contact over a distance of approximately 10,000 km with less power than it takes to power an LED lightbulb, there’s also a lot to be said for the unusual stations that Upon exiting you will get your WSPR station running. Case in point: The other day I looked at WSJT-X and noticed a strange callsign, SA6BSS. After looking at callsigns for a while, you’ll learn which general areas they came from, and I suspected it was a “rare DX” from Europe that is difficult to hit with my antenna from the Pacific Northwest of the country. A quick look at QRZ.com confirmed that SA6BSS is a ham called Mikael Dagman from southern Sweden – cool!
I quickly turned on the WSPRnet map and was surprised to see that Mikael’s station was reporting its position from Alaska rather than Sweden. I zoomed in on the map and found the signal came from a grid hundreds of kilometers south of Unalaska Island in the Aleutian Islands. What on earth would a Swedish ham do in the North Pacific in February?
I wrote a quick email to Mikael about the contact and he has confirmed that I have indeed received a correct position report from his WSPR station which is currently floating around the world on a party balloon! Since he released the balloon on February 23rdIt has traveled from Sweden to the Middle East, across Asia and across the Pacific to the coast of Oregon at an altitude of around 11,000 meters. There it took a hook and went back into the sea; As I write this, I’m heading roughly towards Hawaii.
Literally WSPR around the world – at least halfway there. SA6BSS launched a balloon with a WSPR transmitter that crossed the Pacific on February 23. I copied it when it was south of the Aleutian Islands.
Mikael was kind enough to share some information about the WSPR transmitter he put in his balloon, which is fully solar powered and weighs only 2.6 grams. The saving on its design is almost comical – it’s just a GPS module, an ATMega328, and a Si5351 for the transmitter. It’s a perfect example of what can be done on a budget, which is exactly the concept of “The $ 50 Ham”. Building a lightweight, inexpensive WSPR beacon will of course be the basis for the next installment in this series.