TPSK31: Getting the Trellis Coded Modulation Advantage

摘要

As just about everyone who is alive and awake and not suffering from some awful brain disease knows, PSK31 is an extremely popular mode for doing keyboard to keyboard communications. Introduced in the late 1990's (1,2) it quickly swept the amateur radio world. Its major characteristics are a 31.25 baud differentially encoded PSK signal with keyboard characters encoded into an compression algorithm called varicode by Peter (1) before being modulated with the differentially encoded psk. This differential psk has some serious advantages on HF, including insensitivity to sideband selection, no need for a training sequence to allowing break in decoding to occur and myriad others discussed elsewhere. The slow data rate allows it to use our awful HF channels on 40 and 20 meters effectively and it is more than fast enough to have a good conversation just as we have always done with RTTY. Further, it is very spectrally efficient. If we are going to improve on it, we better not mess with these characteristics. We will not.