"Akula" almost always holds surprises

"Akula" almost always holds surprises when it happens to came across its transmissions, is the case of a recording kindly sent me by my friend ANgazu that is characterized by at least three points:

1) the transmitter was used as soon as it was powered-on or in-standby: you may notice a slight frequency increase of a few seconds, about 37, before reaching the working frequency (figure 1): say that it's a kind of "cold-start" maybe due to an urgency call?

Fig. 1

2) one of the bursts is sent in inverse polarity (figures 2,3)

Fig. 2

Fig. 3

3) the initial bursts consist of a train of pulses (not always of the same number) instead of the usual 500Bd BPSK (figure 4)

Fig. 4

Also notice the transmission of the lower tone before and after the messages, it seems that the involved modems have different behavior. The number of the exchanges is also unusual.

However, it must be borne in mind that the current times are ...quite "particular".

https://disk.yandex.com/d/vlIS_YkqZr3chQ