cars, chameleons, networks... (update 2)

OPL-OPn net (5424.0 KHz)

I have already talked here about this QRG, where the heard ALE addresses were 5B, AB, 1PB, 1PC, 2PB, and 3PB (the so-called PB net), but in these days, at least from 1st December, in that same frequency I heard addresses as OPL, OP1, OP2, OP3, and OP4 (so the name OPL-OPn net). Transmissions start from about 0800 UTC and OPL seems to act as the net-control station. The used technology is the same than PB net, i.e. 188-110A and FED-1052 App.B for the messaging system, and 2G-ALE for the link setup, aside just three 188-110 App.B/FED-1052 App.A frames (see below).

 

Fig. 1

Same QRG and same nodes configuration mean the same source, OS BiH, and the same stations: just a "rotation" of the tactical on-air ALE addresses. I do not know if it's a monthly update or if the update was due to some other reason, further monitorings will help in this direction.

As expected, once removed 188-110A and FED-1052 headers, I got files with ARX and TNEF extensions but this time I had more luck: since the informal nature of the messages (in the reported example, a simple list of sent/received telegrams) these were sent in clear-text. The reading of the extracted files in Figs 2,3 confirms the source and the rotation of the on-air addresses while the e-mail addresses of the network nodes remain unchanged (see Fig.5 of the Part I for what concerns 5PBR), so the old 5B, AB, 1PB, 1PC, 2PB, 3PB,... and the current OPL, OP1, OP2, OP3, OP4,... refer to the same nodes of a single radio-network belonging to OS BiH and running on 5424.0 KHz/USB.

Fig. 2

Fig. 3

Thre is an oddity in one of the recordered transmissions: the presence of three 188-110 App.B/FED-1052 App.A frames just before the link termination (Fig. 4).

Fig. 4

This is the first time, on my side, I see such modality during the e-mail exchanges monitored in this frequnecy: it's hard to say if it just belongs to this transmission or it appeared randomly from some other (unid) source. Anyway, it's worth noting that its time-position in the transmission flow is correct as well as its obsolescence is justified by the use of FED-1052.

https://yadi.sk/d/W19eZn8W32AwPg