WSPR (Amateur radio software)
Encyclopedia
WSPR 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.
Signal (electrical engineering)
In the fields of communications, signal processing, and in electrical engineering more generally, a signal is any time-varying or spatial-varying quantity....
radio communication between amateur radio
Amateur radio
Amateur radio is the use of designated radio frequency spectrum for purposes of private recreation, non-commercial exchange of messages, wireless experimentation, self-training, and emergency communication...
operators
Amateur radio operator
An amateur radio operator is an individual who typically uses equipment at an amateur radio station to engage in two-way personal communications with other similar individuals on radio frequencies assigned to the amateur radio service. Amateur radio operators have been granted an amateur radio...
. 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
Medium frequency
Medium frequency refers to radio frequencies in the range of 300 kHz to 3 MHz. Part of this band is the medium wave AM broadcast band. The MF band is also known as the hectometer band or hectometer wave as the wavelengths range from ten down to one hectometers...
and HF
High frequency
High frequency radio frequencies are between 3 and 30 MHz. Also known as the decameter band or decameter wave as the wavelengths range from one to ten decameters . Frequencies immediately below HF are denoted Medium-frequency , and the next higher frequencies are known as Very high frequency...
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).