WSPR (Whisper)

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

WSPR implements a protocol designed for probing potential propagation paths with low-power transmissions. Transmissions carry a station's callsign, grid locator, and transmitter power in dBm. The program can decode signals with S/N as low as -28 dB in a 2500 Hz bandwidth.
The WSPR protocol compresses the information in the message into 50 binary digits.

WSPR characteristics:

  • data to send:
    • callsign (28 bit)
    • QTH locator (15 bit)
    • power level in dBm (7 bit)
  • speed 1.4648 baud
  • forward error correction
  • continues phase 4-FSK modulation
    • tone separation 1.4648 Hz
  • bandwidth 6 Hz
  • transmission duration 110.6 seconds
  • two-minute time slots for transmitting and receiving.
    • transmissions nominally start one second into an even UTC minute:
      i.e., at hh:00:01, hh:02:01, ... 

Stations with internet access can automatically upload their reception reports to a central database called, which includes a mapping and filtering facility.

WSPR World Watch (Android app)

This app plots radio transmission paths observed in real-time on a world map which can be centered either on the Atlantic or the Pacific.
It also plots the greyline and displays current Space Weather indexes and may optionally plot Aurora ovals.

Theme by Danetsoft and Danang Probo Sayekti inspired by Maksimer