HFU HF Underground

Loggings => Utility => Topic started by: myteaquinn on July 30, 2023, 0534 UTC

Title: Coast Guard Weather broadcast 12575.3 USB 30 July 2023
Post by: myteaquinn on July 30, 2023, 0534 UTC

From 0515 to 0530 The "United States Coast Guard Communications Command" broadcast a weather synopsis and forecast while a digital signal was broadcast in the background. Is this a normal frequency for these weather broadcast?

Title: Re: Coast Guard Weather Broadcast 12575.3 USB 30 JUL 2023
Post by: ~SIGINT~ on July 30, 2023, 1600 UTC

I would think that this is an anomaly. That portion of the band is allocated to maritime narrow-band direct-printing (NBDP) radioprinter and data transmissions.

12575.0 kHz (ch 31) and 12575.5 kHz (ch 32) are non-paired NBDP channels. Operating in any mode other than NBDP in this segment of the band would wipe-out several NBDP channels.

I am receiving some NBDP on 12575.5 kHz. Weak barely readable. Maritime NBDP is typically SITOR-FEC (aka SITOR-B) at a rate of 100 Baud using a standard shift of 170 Hz. I am giving Black Cat NAVTEX SITOR-B v1.0.0 a test run to see what I can decode on this channel. No luck so far.

80.361 Frequencies for narrow-band direct-printing (NBDP), radioprinter and data transmissions.
https://www.ecfr.gov/current/title-47/chapter-I/subchapter-D/part-80/subpart-H/subject-group-ECFRc6d6b33c0e67cb3/section-80.361 (https://www.ecfr.gov/current/title-47/chapter-I/subchapter-D/part-80/subpart-H/subject-group-ECFRc6d6b33c0e67cb3/section-80.361)

https://www.govinfo.gov/content/pkg/CFR-1998-title47-vol5/xml/CFR-1998-title47-vol5-sec80-361.xml (https://www.govinfo.gov/content/pkg/CFR-1998-title47-vol5/xml/CFR-1998-title47-vol5-sec80-361.xml)


Here are the US Coast Guard Frequencies. They use 12579 for NBDP.

Marine Weather Broadcasts from the USCG
https://www.weather.gov/marine/uscg_broadcasts (https://www.weather.gov/marine/uscg_broadcasts)

Title: Re: Coast Guard Weather broadcast 12575.3 USB 30 July 2023
Post by: myteaquinn on July 30, 2023, 2333 UTC

Thanks for the info SIGINT. I was trying to decode the digital signal using fldigi. One of the modes I tried was SITOR-B but did not get any decode.

Title: Re: Coast Guard Weather Broadcast 12575.3 USB 30 JUL 2023
Post by: ~SIGINT~ on July 30, 2023, 2352 UTC

No luck either with decoding the transmission. They are short and most likely just an ID, no message traffic --- but it was fun trying anyways.

This PDF (HF NBDP Database for DXers v1.1) is a nice addition to have.
https://www.ndblist.info/index_htm_files/worldNBDPdatabase.pdf (https://www.ndblist.info/index_htm_files/worldNBDPdatabase.pdf)

You can find it at the bottom of the ndblist.info Datamodes Section:
https://www.ndblist.info/datamodes.htm (https://www.ndblist.info/datamodes.htm)


~SIGINT~