USCG NavCen 12.5 kHz split marine channel frequency errors?

AM909

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At USCG NavCen Maritime VHF Narrowband Channels - 12.5 KHZ there is a table of 12.5 kHz split marine channels authorized under 47 CFR 80.371(c)(iii). Based on the how I understand it, there appear to be three errors in the table, which I also find in Monitoring Times, July 2004, p. 16.

  • Channel 279 Ship TX says 156.9775, but 156.9875 is the correct 12.5 kHz split between adjacent channels 20 and 79.
  • Similarly, channel 279 Coast TX says 161.5775, but 161.5875 is the correct 12.5 kHz split between adjacent channels 20 and 79.
  • Channel 287 Ship TX says 158.3875, but 157.3875 is the correct 12.5 kHz split between adjacent channels 28 and 87.
Can someone familiar with the subject confirm this? If there were a reason for the inconsistencies, I'd expect it to have been in the law and documented in a note to the table or something. I looked at a manual for an apparently current production radio – the Cobra MRF77 – and it doesn't appear to support the split channels, despite their being authorized in 1998. There's no mention of them in the RRDB wiki.

I submitted a report via the NavCen website's contact page.
 

tyytor

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At USCG NavCen Maritime VHF Narrowband Channels - 12.5 KHZ there is a table of 12.5 kHz split marine channels authorized under 47 CFR 80.371(c)(iii). Based on the how I understand it, there appear to be three errors in the table, which I also find in Monitoring Times, July 2004, p. 16.

  • Channel 279 Ship TX says 156.9775, but 156.9875 is the correct 12.5 kHz split between adjacent channels 20 and 79.
  • Similarly, channel 279 Coast TX says 161.5775, but 161.5875 is the correct 12.5 kHz split between adjacent channels 20 and 79.
  • Channel 287 Ship TX says 158.3875, but 157.3875 is the correct 12.5 kHz split between adjacent channels 28 and 87.
Can someone familiar with the subject confirm this? If there were a reason for the inconsistencies, I'd expect it to have been in the law and documented in a note to the table or something. I looked at a manual for an apparently current production radio – the Cobra MRF77 – and it doesn't appear to support the split channels, despite their being authorized in 1998. There's no mention of them in the RRDB wiki.

I submitted a report via the NavCen website's contact page.
Hi I have ran across this sort of type of thing several times, not being critical but they type things up, some times not proof reading them or no knowing about frequency spacing.
 

Airboss

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At USCG NavCen Maritime VHF Narrowband Channels - 12.5 KHZ there is a table of 12.5 kHz split marine channels authorized under 47 CFR 80.371(c)(iii). Based on the how I understand it, there appear to be three errors in the table, which I also find in Monitoring Times, July 2004, p. 16.

  • Channel 279 Ship TX says 156.9775, but 156.9875 is the correct 12.5 kHz split between adjacent channels 20 and 79.
  • Similarly, channel 279 Coast TX says 161.5775, but 161.5875 is the correct 12.5 kHz split between adjacent channels 20 and 79.
  • Channel 287 Ship TX says 158.3875, but 157.3875 is the correct 12.5 kHz split between adjacent channels 28 and 87.
I submitted a report via the NavCen website's contact page.
As a member of the MT editorial staff, I remember this like it was yesterday. For the record, the MT Staff also submitted a correction to the NavCen page for the three errors which I see have still not been corrected that you cited in your post. That does not surprise me.

In the MT article that Gayle Van Horn wrote, the 12.5 kHz table was brand new at the time. The Congressional mandate to narrowband had a lot of folks in and out of government scurrying about and the FCC and NTIA both had some errors in some of their docs initially. We actually footnoted the three errors in that table in that piece, but that footnote was accidentally left off by the layout staff after that editted copy left our hands (that table was the last item on the last page of the feature). In final edits, it was not caught by either me or the managing editor until after we had gone to press. So on behalf of the former staff, I apologize.

In the Maritime Communications rules published on Nov 8, 2004 (Maritime Communications) the FCC mentioned the 12.5 kHz splits but they were not incorporated into the freq table. I haven't had a chance to dig into the current federal CFR docs to see if the error still exists there or not.

To be honest, administratively the situation now is not much better. In the current ITU 2020 Radio Regulation docs Vol 2, Appendix 18 (Rev in WRC-19) the table of transmitting frequencies in the VHF maritime mobile band does not show any of the 12.5 channels, but the footnotes for that table do mention them by freq range only, no individual assignments.

We live a bit far from the Tennessee River system to see how much narrow banding has been incorporated into the VHF marine spectrum, so I am curious what others are hearing.

Funny this has come up as I have been doing a deep dive into the current HF marine band plan lately for a project I am working on and the VHF freqs were next on my list. Thanks for reminding me of the 3-12.5 kHz freq errors.

Larry

Former Monitoring Times editor
 

AM909

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@Airboss: I was curious as to where the table came from because it's not in the rule or the law as amended (at 69 FR 64674 (¶24), amending 47 CFR 80.371(c)(1)(iii)). As you said, there's no specific table of split channels – it just says it allows using the splits between existing channels under certain conditions. Anyway, it's good to have agreement that they are, indeed, errors. I got a "we've forwarded it to the appropriate subject matter expert" response from NavCen, so we'll see if it gets fixed this time. :)
 
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AM909

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@Airboss: NavCen has responded that the table came from Recommendation ITU-R M.1084-5 (03/2012 version linked), which shows the correct frequencies for channel 279, but not the correct one for channel 287. I've responded to NavCen and informed ITU.
 

Airboss

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Interesting that the current ITU RR doesn't have this info. Thanks for the link to where it really came from.

Larry
 

mmckenna

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ITU has this posted, but it's a b*tch to find.

ITU also has a document looking at the future of marine VHF, and has 6.25KHz digital channels. Not sure if it's been adopted, and no plan to go there anytime soon.
 

milf

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Just like with railroads, there are some on here that WILL tell you never happening, don't bother. These radio wannabe Gods will also tell you that the 6.25 NXDN for maritime will also never happen. Add them, and you just might find some interesting communications on the new splits. "Mainstream" may not be using them all fulltime for a bit, but its not like your killing your scanner to load them in.
 

nsrailfan6130

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Thanks Milf, yeah, That was my question if they were being used in a full-time basis as of yet. I just posed my question wrong.

Just like with railroads, there are some on here that WILL tell you never happening, don't bother. These radio wannabe Gods will also tell you that the 6.25 NXDN for maritime will also never happen. Add them, and you just might find some interesting communications on the new splits. "Mainstream" may not be using them all fulltime for a bit, but its not like your killing your scanner to load them in.
 
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