FIGURE 4. Block diagram for the WSPR receiver.
(W1BW). The open source software runs on Windows,
Linux, and other systems. It is available from
www.physics.princeton.edu/pulsar/K1JT as a free
WSPR utilizes the internal or external sound card of
your PC/MAC (see Figure 3). These cards have good
specifications. Foremost are the data converters providing
a large 90 dB dynamic range which is used to the fullest.
WSPR is programmed to send and receive messages
through the card. Here’s more about WSPR protocol.
WSPR uses time-synchronized communications based
on Coordinated Universal Time (UTC). Transmissions last
somewhat less than two minutes each, nominally starting
one second into an even UTC minute. Hence, it is
important for your computer to be accurate to within a
second or so of UTC. So, set your computer clock to an
accurate source such as
Since most computer clocks drift, you will need to
update your clock periodically.
FIGURE 5. WSPR receiver