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« on: October 06, 2023, 0750 UTC »
Hi.
Shift is 170 Hz, I guess you mean "Offset"...
As this is an FSK transmission the center frequency (CF) and window frequency (WF, or dial frequency DF) for this mode is both 8414,5 kHz - right between "mark" and "space". This is valid for ANY fsk mode on HF - RTTY, SITOR (including DSC), FAX, STANAG4481 etc.
What you are using as window frequency (WF) or dial frequency (DF) is depending on the decoder/modem you are using. Normally the offset for DSC is 1700 Hz (a.f.a.i.k. defined by ITU and IMO for the maritime mobile service on HF, including GMDSS). Same with NAVTEX on 490 and 518 kHz - that is the CF transmitted, despite the fact if it is modulated by a modem or directly by the transmitter.
On the other hand we have those PSK, OFDM, BPSK etc. modes where CF and WF are different (STANAG4285, MIL-STD 188-141, MIL-STD 188-110 etc.). The offset for S4285 for example is 1800 Hz so you have a WF/DF of let's say 3998,2 kHz and a CF of 4000,0 kHz.
Please be aware of this difference in modulation and demodulation of any frequency shift keying - from RTTY, SITOR-A/-B (and DSC), NAVTEX, STANAG4481, DPRK-FSK, AKKORD and so on.
Hope this helps.