6505 kHz digital signal - mixed modes

[alleycat]

I can never seem to find a good match at SigIDWiki for the stuff I hear   Closest match appears to be "Saab Grintek MHF-50 MFSK Modem" but that's a South African mode and I don't think that's what I'm receiving loud & clear in NE North America. Going for a while not at 0350z on 6505 kHz - approximately 2.5 kHz-wide digital signal that cycles between several different modes; one sounds like RTTY, another has multiple tones. Audio sample at https://www.lutins.org/temp/6505.mp3 and waterfall at https://www.lutins.org/temp/6505.JPG. Any help appreciated!  73 de KC2KLC

[Token]

Yes, that is the Saab Grintek MHF-50 modem you are hearing.  Yes it is used by the South African Navy.  Yes it can be hear din the US, I can even hear it here on the west coast.  The 6504 kHz USB channel has been RFDFed and TDOA geolocated to South Africa.  You can often find it on 3 or 4 frequencies simultaneously, for example when you hear it on 6504 kHz USB also check 8580 kHz, 12982 kHz, and 16986 kHz.

T!

[alleycat]

Wow, wasn't expecting an S10 signal from South Africa - I guess their military is projecting serious world-wide coverage. Thanks for confirming that and a blessed and healthy new year to you!

[~SIGINT~]

Saab Grintek MHF-50 MFSK Modem being heard in Toronto, Ontario Canada. Signal is at approx -100 dBm on 6504.0 kHz USB at 02:28z, 2021-02-01. I had previously intercepted this station on 2020-11-13 at 02:24z.

RSPduo and receiving on both the Barker & Williamson antenna and Wellbrook loop.

[QRP]

8580 kHz is a common frequency for this signal, and is often paired with 4346, 6504 and 12982 kHz USB. They all carry the same message(s) over and over so they are believed to be either channel markers, propagation markers and/or information about status of other South African Navy working channels on the bands. 4245, 6407, 6493 and 8603 kHz are believed to be the above mentioned working channels and carry the actual messages because the length of transmissions may vary.

https://www.sigidwiki.com/wiki/Saab_Grintek_MHF-50_MFSK_Modem