Nowadays, one of the most impressive QRP modes is Joe Taylor, K1JT’s WSPR (pronounced “whisper”) mode. WSPR stands for “Weak Signal Propagation Reporter.” Programs written for WSPR mode are designed for sending and receiving low-power transmissions to test propagation paths on the MF, HF and recently, UHF bands. The process is similar to a beacon. Users with Internet access can watch results in real time at wsprnet.org.
Pablo, WA6RSV, alerted us to the fact that not everyone realizes what a Raspberry Pi is. He said, “One week ago I thought a Raspberry Pi was a dessert! (I like apple pie!). Nobody explained to me that it is a normal computer just like your Mac or PC.” It comes without a monitor, mouse or keyboard (you don’t need them for this application). You program a microSD card (from a file listed below on this webpage), plug it into the Pi and you have a powerful single board computer. The microSD card contains the operating system (linux) and all of the software.
TAPR offers two versions of a WSPR “hat” to use with Raspberry Pi single-board computers.
The WSPR-Pi for 20M
The WSPR-Pi (also known as “QRPi”) is Zoltan, HA7DCD’s transmitter for 20M. It uses surface mount components and comes fully assembled and ready to go. Here is a link to the setup manual and here is a link to Zoltan’s presentation at the 2015 DCC.
WWoT for 30 and 40M
WSPR Without Tears is Bruce Raymond, ND8I’s project to simplify the process of getting an actual transmitter up and running so you can enjoy working with WSPR and avoid dealing with the headaches associated with building a working system. What makes it really interesting is that WSPR is optimized for operating at very low power. The WWoT board puts out a whopping 200 mW which is capable of reaching impressive distances even with a bad antenna (see the map above for typical response using an-end fed dipole in an attic).
The WWoT board (or shield as referred by the community today) is an inexpensive way of turning a Raspberry Pi (Pi) single-board computer into a WSPR transmitter.
Our approach uses a Raspberry Pi computer ($35) to generate WSPR transmissions. Our board plugs into a Raspberry Pi and amplifies and filters the output (the Raspberry Pi output is a very low power square wave that would be illegal to transmit due to its harmonic content). The Raspberry Pi generates the WSPR signal in software and utilizes timing data from the Internet to calibrate its internal clock and transmit frequency, so you don’t have to do it.
So join the group of Whispering Raspberries on 30 and 40 meters by ordering a TAPR 30M or 40M WSPR-Pi today. Heck, get one of each and double your fun!
NOTE: the “WSPR Without Tears” kit does not include the Raspberry Pi, power supply, microSD card or antenna.
Here are links to files for the WWoT units: