WSPR, though pronounced “whisper”, it does not mean “be quiet”.
It stands for Weak Signal Propogation Report, a digital mode of radio transmission used to test air wave propogation (signal travel) for your antennas.
Now I was not testing any antennas and you can run this mode off of your regular rig (expensive to tie up an HF Transciever for this) but I wanted to build a learning kit with the Raspberry Pi. I picked up a $25 transmitter board (TAPR 20) that attaches to the Pi to transmit a 10mw (very weak signal) in the 14.0971 mhz range (20 meter ham band).
I ordered a 2nd Pi (my 1st is permanently being used as a DStar HotSpot), picked up a length of 18ga wire and cut a piece 16.5 feet for an antenna. I solder tinned the wire end and attached it to the device. The board directions were not the greatest and I had some trouble getting it “Spotted”. Turns out I had connected it to the wrong tap on the board and 30 minutes after switching it, I got “Spotted”
The signal itself is a timed broadcast beacon (110.6 seconds beginning 1 second after each full minute UTC). There are stations around the world monitoring for these “broadcasts” and they report the call sign and time of each signal heard to WSPRnet.org.
Here are a couple reports on my signal….