(a joint analysis by me and ANgazu)
9MR 9/10/13 RMMJ MRB MRB RYRYRYRY 9MR 9/10/13 RMMJ MRB MRB SGSGSGSGSG AR JULL JULL
is the Id & "RY/SG" test tape transmitted by 9MR Royal Malaysian Navy (RMN) [1], picked up using the VR3BG KiwiSDR located in Hong Kong and tuned on 8461.1 KHz and 6483.1 (CF).
The signals exhibit two curious features, at least in the heard test trasmissions: the first consists of the used 50Bd async FSK waveform with the non-standard and quite uncommon 900Hz shift value (Fig. 1).
The second feature is the framing which is used during the test operations: as you may see in Figs. 2 and 3, they use ITA2 code (5x28) with alternating framings 5N1/5N2, i.e., a character sent with 1 stop bit followed by a character sent with 2 stop bits:
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This odd system causes the 15-bit period visible either in the raster of SA either in the bitstream (the latter reshaped to 30-bit in Figure 2). When a block ends, it possibly uses a special character or new line that causes te one bit shift to the left. So far, we never seen such mode.
It must be said that many reports indicate the ITA2 framing 5N1 and the FSK waveform 50Bd / 850Hz: these are obviously errors caused by the "goodness" of many decoders which can correctly decode these test tape transmissions even with slightly wrong settings.
During the last days monitoring we have not yet had the chance to hear traffic on the two mentioned frequencies, just test transmissions, so we can't say if they always use the same shifted 5N1/5N2 framing also in traffic mode: we hope to have better luck in the next days/weeks. By the way, our TDoA direction findings (6483.1 KHz signal) point to Tanjung Gelang, site of RMN's Fleet HQ of the Naval Region I.
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| Fig. 1 - 900Hz shift |
This odd system causes the 15-bit period visible either in the raster of SA either in the bitstream (the latter reshaped to 30-bit in Figure 2). When a block ends, it possibly uses a special character or new line that causes te one bit shift to the left. So far, we never seen such mode.
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| Fig. 2 |
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| Fig. 3 |
It must be said that many reports indicate the ITA2 framing 5N1 and the FSK waveform 50Bd / 850Hz: these are obviously errors caused by the "goodness" of many decoders which can correctly decode these test tape transmissions even with slightly wrong settings.
During the last days monitoring we have not yet had the chance to hear traffic on the two mentioned frequencies, just test transmissions, so we can't say if they always use the same shifted 5N1/5N2 framing also in traffic mode: we hope to have better luck in the next days/weeks. By the way, our TDoA direction findings (6483.1 KHz signal) point to Tanjung Gelang, site of RMN's Fleet HQ of the Naval Region I.
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| Fig. 4 |
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| Fig. 5 |
https://yadi.sk/d/d15nXWys6iSuIg (6483.1 KHz)
https://yadi.sk/d/2gmoADztQTwT0w (8461.1 KHz)