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Quick Start Guide for WSPR v0.7


WSPR (pronounced "whisper") stands for "Weak Signal Propagation Reporter".

This program implements transmitting and receiving functions for a digital soundcard mode called "MEPT_JT", or simply "the WSPR mode".

WSPR generates and receives signals using structured messages, strong forward error correction, and narrow-band 4-FSK modulation. Its principal design goal is reliable copy at very low signal levels. In practice it works well at signal-to-noise ratios down to about -27 dB in a reference bandwidth of 2500 Hz.


1. Download WSPR from the WSJT home page,

2. Run the resulting executable file to install WSPR.

3. Start the program by double-clicking on its desktop icon.

4. Open the Setup -> Options menu and enter your callsign and 6-character grid locator.

5. Enter the COM port number to be used for PTT control in the box labeled PTT Port. (For example, enter 1 if you will use COM1.) Enter 0 if you will use VOX control.

6. If you have more than one sound card and do not wish to use the Windows default sound card for WSPR, examine the list of sound devices in the console window (the one with black background).
Enter the desired device numbers in the boxes labeled Audio In and Audio Out.

7. Enter your transmitter power in dBm in the appropriate Options box.

8. On the main screen, enter your SSB transceiver dial frequency and desired Tx frequency in MHz. Your transceiver should be set to USB mode. (You can also set the Tx frequency by double-clicking with the mouse on the waterfall display, after setting the Dial frequency.)

9. Click on "Rx" to receive only, on "Tx" to transmit only, or on the desired average percentage of transmission cycles. In this case the program will decide whether to transmit or receive during any given two-minute interval, and will do so in such a way as to randomize your T/R pattern. This procedure will maximize your chances of receiving any other WSPR station operating within a +/- 100 Hz range centered 1500 Hz above your dial frequency.

10. Be sure that your computer clock is correct to +/- 1 second. If necessary you can make small adjustments by left- or right-clicking on the "Dsec" label.

11. WSPR will begin a Tx or Rx sequence at the start of each even UTC minute. The waterfall will update near the end of each Rx sequence.

12. Check the box "Upload spots" if your computer is connected to the internet and you want your received spots uploaded to the WSPRnet database. For infomation on this excellent resource, direct your browser to

Decoded Output

In normal operation WSPR displays a single line of output for each decoded signal, in the following format:


Date  UTC    dB  DT Freq Drift  W  Message
080427  2016 -5 0.5  10.140197 0 0.5 VE1VDM FN85 27
080427  2016 2 0.8 10.140215 0 0.5 NJ0U EN71 30
080427  2016 -10 0.8 10.140233 0  0.6 F6IRF JN35 30
080427  2016  -20 0.7 10.140275 3 0.5 G4DZU IO93 30
080427 2020 -14 0.8 10.140156 0 0.7 N1NCO FN42 30
080427 2020 2 1.6 10.140285 0 0.9 K3SIW EN52 30
080427 2022 -18 1.6 10.140185 0 0.4 K7UV DN31 30
080427 2022 -21 0.8 10.140193 0 0.6 WW7Y DN40 30
080427  2022 2 0.8 10.140215 0 0.4 NJ0U EN71 30
080427 2022  -21 1.0 10.140233 0 0.5 W1BW FN42 20
080427  2022 -26 0.0 10.140247 0 0.7 PA3GLG JO21 30
080427  2024  -3 1.4 10.140188 0 0.4 KQ8RP EN80 30
080427  2024 -5 0.5 10.140197 0 0.4 VE1VDM FN85 27
080427 2024 -9 0.8 10.140232 0 0.6 F6IRF JN35 30

The meanings of the colums are as follows:

dB: Received S/N in the standard reference bandwidth of 2500 Hz.
DT: Offset between computer clocks at Tx and Rx stations.
Freq: Measured frequency of received signal (MHz).
Drift: Apparent drift of received signal (Hz/minute).
W: Spectral width of signal after removal of tone steps (Hz).

Time offsets DT greater in magnitude than about +/- 2 s indicate a significant timing error at the transmitter or receiver, or possibly both. For best performance your computer clock should be kept accurate to within +/- 1 s.

Apparent frequency drifts greater that +/- 1 Hz per minute most often occur at the transmitter, and should be corrected for best performance. (Of course, receiver drift could also contribute, but receiver drifts are easily recognized because nearly all signals appear to drift by the same amount.)

Color coding is used in the bandmap to indicate how long it has been since a particular station was last decoded. Red calls have been seen within 15 minutes of the last line of decoded text. Yellow callsigns are 15-30 minutes old, light gray 30-45 minutes, and darker gray 45-60 minutes. After one hour calls are eliminated from the list.

-- 73, Joe, K1JT

Email: k1jt at arrl dot net

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