8 September 2017

K4MT/NT9P Net, Russian Intel/Diplo (M42b)

K4MT/NT9P network, also known as Enigma designator M42b, is a quite common Russian Intel/Diplo network which uses both CW-Morse and FSK 50Bd/500: I spotted several trasnmissions this morning on 12164.0 Khz, just before a G3 (strong) geomagnetic storm passing: FSK is transmitted with its cf at +1000Hz.

Fig. 1
In this recording, FSK follows a CW call "NT9P NT9P NT9P DE K4MT K4MT K" and in turn it's followed by a "CFM QRU K" request: most likely the CW is used for setup or operators chat. The FSK is a Baudot 5FG coded stream using a preamble and 7-bit period (fig. 2):

Fig. 2
note the markers at every group of 50 x 5FGs (Fig. 3):
Fig. 3

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