PSK31

PSK 31 is the Acronyme of Phase Keying Shift, 31 Baud , a form of conversational Modulation of keyboard with keyboard of the type Radiotélétype. She was invented in the Années 1990 by a Radioamateur Polish then developed by another British radio ham.

Transmission speed, approximately 50 words per minute, is relatively slow compared to the RTTY. The popularity of PSK31 was made of word of mount very quickly at the point have supplanted the RTTY which however keeps still its followers.

Principle

The letters are represented by a Codage of Huffman: each letter is coded by a succession of bits variable length, as in Morse code. Particular coding used is called Varicode .

Here some examples of small letters and capital:

Some examples of punctuation:

: 111110111 *]: 111111011
{ : 1010110111
} : 1010110101

As in any code of Huffman, the less frequent letters have codes longer than the more frequent letters. For example, contrary to the E, the letter Q, not very current in the English vocabulary, has a voluntarily long code.

The sequences of bits are transmitted in the following way:

The 0 corresponds to a signal in opposition of phase with the Porteuse, and the 1 with the Porteuse itself.

Advantages

greater facility of use than RTTY;
low bandwidth 31,25 Hz compared to the RTTY (300 Hz) and especially with the transmission in phone (3 Khz),

Disadvantages

required of a good stability of the transmitter in emission;
the characters are transmitted on line . There is thus no real possibility to correct the typing errors. A support on the key of correction sends to the receiving station an error code. The correspondent thus sees the error: the erroneous letter is posted initially, then the cursor retrogresses and the correct letter is posted.

Allocated frequencies of use

3580 Khz
7035 Khz
10145 Khz
14070 Khz
18100 Khz
21080 Khz (but actually 21070)
24920 Khz
28120 Khz

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