Using WSPR on Microsoft Windows XP, Vista, or Windows 7

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WSPR Overview

WSPR (pronounced "whisper") stands for “Weak Signal Propagation Reporter.” The WSPR software is designed for probing potential radio propagation paths using low-power beacon-like transmissions. WSPR signals convey a callsign, Maidenhead grid locator, and power level using a compressed data format with strong forward error correction and narrow-band 4-FSK modulation. The protocol is effective at signal-to-noise ratios as low as –28 dB in a 2500 Hz bandwidth. Receiving stations with internet access may automatically upload reception reports to a central database. The WSPRnet web site provides a simple user interface for querying the database, a mapping facility, and many other features.

WSPR 2.1

WSPR 2.1 is the latest version WSPR, the “Weak Signal Propagation Reporter.” It differs from WSPR 2.0 by including support for software defined radios (SDRs) like the HPSDR/PowerSDR rig. With I/Q mode enabled, the program uses 2-channel sampling at 48000 Hz for both input and output. Your HPSDR PowerSDR sends I and Q baseband signals to the WSPR 2.1 input; the WSPR2.1 audio output, also in I/Q format, goes to the HPSDR PowerSDR Tx audio port. T/R switching is accomplished via a virtual serial port. You will need Virtual Audio Cables and Virtual Serial Ports to finish the implementation. Experience has indicated that the traditional audio in and out should be tried first to establish a performance baseline before the I/Q implementation is attempted.


1. WSPR 2.1 can be downloaded from the WSJT Home Page. Click on the WSPR link at the left margin and then on the appropriate download link. Install the program in the usual way for your operating system. Under Windows, execute the downloaded file and follow the installation instructions. During a test period you may wish to have both WSPR 2.0 and WSPR 2.1 available on your computer; in this case you should install WSPR 2.1 in a new directory, for example the Windows folder C:\HamRadio\WSPR21. (In the Vista or Windows 7 operating systems, if you use the default location C:\Program Files\WSPR you may need to set some access permissions explicitly.)

2. Follow the WSPR On-Line-Help file to set up the program. Pay close attention to the instructions on time synchronization and frequency calibration using the built-in features of WSPR.

3. Install at least two sets of com0com ports for use with PTT and frequency control. Learn about and install com0com.

4. Install Virtual Audio Cable (VAC). Follow FlexRadio instructions at: How to Setup Virtual Audio Cable (VAC) 4.0x with PowerSDR 1.x

5. Change the calibration values as described in the FlexRadio Knowledge Base article:How to Configure WSJT with PowerSDR and VAC

6. For best decoding of weak signals, PowerSDR's AGC should be set to custom and the AGC-T adjusted for 0dB audio input level.

7. A good frist test will be to tune to WWV on DIGU and set your RX with RIT to -1500 Hz. You should see a solid line at the reference or center frequency. If not adjust your frequency calibration so that it is on the mark. W9KFB's RX required a correction value of 1.00004692000000 with excaliber installed. While you are at WWV also check the time ticks with the PC clock so you know that your time synchronization is working.

8. Real time task management - This software set is very sensitive to throughput, and the lack of throughput will prevent successful decoding and sending signals. Watch for signs of task interference on the waterfall displays. If you se such signs, take steps to remove the interfering tasks.