Technical Articles

Hey Hams, Let’s Give a Shout Out to WSPR!

When I want to check for information on propagation conditions, I often look at the N0NBH solar-terrestrial data banner that appears on many ham radio sites. But if you want to analyze propagation in real time, a better way is to monitor beacons. If you can receive the beacon, there’s an open path between you and the beacon’s location.

Wouldn’t it be cool to transmit your own beacon from your QTH and actually see reports from dozens of receivers around the world that are receiving your signals? Or maybe you have more than one antenna available and you want to know which is really best to get your signal to the desired location? Try WSPR.

Just WSPR

Traditional beacons usually use CW because these beacons are easy to build and don’t require much power to be effective. But with the current interest in digital communications, there’s an increased use of more advanced digital systems like WSPR. Pronounced “whisper,” this stands for Weak Signal Propagation Reporter. It is a computer program used for weak‑signal radio communications between ham radio operators. The program was initially written by Joe Taylor, K1JT, but is now open source and continues to be improved and refined on a regular basis.

WSPR is designed primarily for sending and receiving low‑power transmissions to test propagation paths on the MF and HF bands. Transmissions carry a station’s callsign, Maidenhead grid locator, and transmitter power in dBm. The signal is frequency shift keying (FSK) with a very small shift and a very slow rate. The bandwidth occupied is only about 6 Hz, so many stations can operate within the 200Hz WSPR window without interference.

Each transmission lasts for less than two minutes and starts at the beginning of each even‑numbered minute. It is very important that transmitters and receivers are in sync, so successful WSPR operation depends on an accurate clock. A GPS is recommended for best clock stability.

Receiving stations with Internet access can automatically upload their reception reports to a central database called WSPRnet, which includes a mapping function and a recent activity log by band. You can also track activity on your own using K1JT’s WSPR software and your computer.

There’s one caveat regarding WSPR beacon operations. According to 97.203 of FCC regulations, any beacons–including WSPR–can be operated 24/7 unattended on 10m and above. If you are operating on other HF frequencies, a control operator should be present to comply with part 97 rules.

Start WSPRing

SOTAbeams WSPRlite Flexi is a self‑contained propagation beacon transmitter. Once it’s configured using a special Windows or Android app (third-party LINUX and Mac support available at WSPRlite Facebook Group), WSPRlite Flexi only needs a USB power supply to operate. WSPRlite is capable of operating 630, 160, 80, 40, 30, 20, 17, 15, 12, 10 and 6 meters, but requires external low-pass filters to suppress unwanted harmonics.

WSPR Frequencies:

Band                                     Dial Freq. (MHz)             Transmit Freq. (MHz)

160m                                     1.836600                             1.838000 ‑ 1.838200

80m                    3.592600                      3.594000 ‑ 3.594200

60m                                       5.287200                             5.288600 ‑ 5.288800

40m                                       7.038600                             7.040000 ‑ 7.040200

30m                                       10.138700                           10.140100 ‑ 10.140300

20m                                       14.095600                           14.097000 ‑ 14.097200

17m                                        18.104600                           18.106000 ‑ 18.106200

15m                                        21.094600                           21.096000 ‑ 21.096200

12m                                        24.924600                          24.926000 ‑ 24.926200

10m                                       28.124600                           28.126000 ‑ 28.126200

6m                                          50.293000                          50.294400 ‑ 50.294600

2m                                          144.488500                        144.489900 ‑ 144.490100

The results of some experimental transmissions from my QTH in Ohio are shown in the illustration below captured from www.wsprnet.org. There are two maps available, as well as a chart of signal reports. The antenna used was a Mosley tri-bander pointed west, and the output power was typically around 180mW on 20 meters. You’ll notice there were signals received off the back and side of the beam as well.

More Info

Need some help or advice? Start with the experts at DX Engineering. You can find updates and tech information about the WSPRlite from SOTAbeams. And be sure to check out WSPRnet.org.

There are also online groups of WSPR users and information sites you can visit:

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