Weak Signal Propagation Reporter (WSPR, pronounced:” whisper”) is a protocol developed by John Taylor, K1JT in 2008. It’s one of the many protocols used by radio amateurs but WSPR is a special one. The “Weak Signal”-part refers to signals being transmitted with a maximum power of 5 Watt (37 dBm), what still is regarded as QRP. But you can use much less then 5 Watt. Use more power is pointless, because it removes the accuracy of the “Propagation Reporter”-part.

Software
You need special software to run WSPR. Once installed, the program needs an audio connection with your HF-rig. When you already doing digital modes, you probably have such a connection. If not, look for a device like a Signalink which is basically a external soundcard with a converter to your rig. Some modern rigs do have a soundcard onboard which you can connect to from your computer via USB.
When your sound connection with the rig is already up, you’ll see in the left lower corner the audio level the program is receiving. Adjust until it’s around 0 db (isn’t really that critical). Now do a minimal configuration, hit [setup] and fill in your call, locator, select audio device that is connected to your rig, power (37dBm = 5 Watt).
Now we need to determine how to key the rig. If you have a serial connection to your rig to control PTT and your rig is in the pull down list, you can select it. When your rig isn’t in the list I would suggest you use VOX. When you uncheck the idle-box the program will start it’s transmitting interval. Check that the soundlevel while transmitting isn’t overload the ALC-level on your rig.
Set your rig in USB-(data)modus (also below 10MHz) and use the designated WSPR-frequenties:

WSPR uses a slightly different frequency to transmit, but you don’t have to adjust that on your rig, that’s done automatically. Just use the above frequencies to set your VFO to. Of course don’t forget to turn down your rig output power to a maximum of 5 Watt and you’re good to go. Just let WSPR run for a few hours and see what it’s picking up.

QSL
I’ve seen amateurs who want confirmation on WSPR contacts via eQSL. I don’t know if you can speak of a real contact if there is no human interaction involved anymore, but that’s something for another discussion.

WSPRnet
If you want a graphical presentation of your WSPR-contacts check out wsprnet.org. It’s quit interesting to see all these lines across the globe from your station to others! And finally you can see graphically what propagation is doing on that particular band. And that’s what WSPR is all about.