29 June 2015

Unid OFDM 16-tone 75 Bd, 110 Hz (MS 188-110A App.A modified?)

I had this signal via Twente SDR on USB 14301.8 (cf)  on 28/06/15 (1710z) just in the well-known 20 mt reserved band, an that's a bit odd.
The waveform is an OFDM 16-tone PSK, 75 Bd and 110 Hz shift, sent in burst mode. It is very similar to the obsoleted Standard NATO MIL 188-110A Appendix A without the doppler tone @ 605 Hz and in not-continuous mode.
OFDM parameters
There is a Chinese variant of the MIL 188-110A 16 channels: it could be this case, but I could not find info or logs about it. The burst mode could lead to something like a selcall waveform but the ~720mS spaced "pips" looks like a TDMA.
Hope to get more info and/or more records.

A short recording can be downloaded from here:

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