WSPR (Amateur radio software)
WSPR (pronounced "whisper") stands for "Weak Signal Propagation Reporter.". It is a computer program used for weak-signal radio communication between amateur radio operators. The program was initially written by Joe Taylor, K1JT, but is now open source and is developed by a small team. The program is designed for sending and receiving low-power transmissions to test propagation paths on the MF and HF bands.
WSPR implements a protocol designed for probing potential propagation paths with low-power transmissions. Normal transmissions carry a station's callsign, Maidenhead 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. Stations with internet access can automatically upload their reception reports to a central database called WSPRnet, which includes a mapping facility.
Protocol specification
- Standard message: callsign + 4-digit locator + dBm (i.e. K1ABC FN20 37)
- Messages with a compound callsign and/or 6-digit locator use a two-transmission sequence. The first transmission carries compound callsign and power level, or standard callsign, 4-digit locator, and power level; the second transmission carries a hashed callsign, 6-digit locator, and power level. Add-on prefixes can be up to three alphanumeric characters; add-on suffixes can be a single letter or one or two digits.
- Standard message components after lossless compression: 28 bits for callsign, 15 for locator, 7 for power level, 50 bits total.
- Forward error correction (FEC): convolutional code with constraint length K=32, rate r=1/2.
- Number of binary channel symbols: nsym = (50+K-1) * 2 = 162.
- Keying rate: 12000/8192 = 1.4648 baud.
- Modulation: continuous phase 4-FSK, tone separation 1.4648 Hz.
- Occupied bandwidth: about 6 Hz
- Synchronization: 162-bit pseudo-random sync vector.
- Data structure: each channel symbol conveys one sync bit (LSB) and one data bit (MSB).
- Duration of transmission: 162 * 8192/12000 = 110.6 s.
- Transmissions nominally start one second into an even UTC minute: i.e., at hh:00:01, hh:02:01, ...
- Minimum S/N for reception: around –28 dB on the WSJT scale (2500 Hz reference bandwidth).
History
WSPR was originally released in 2008.
References
External links