Our good friend Mike Chase-Ortiz had been using the SDR.hu TDoA network tool and has pinpointed several of the US Navy NATO RTTY (aka Stanag 4481) broadcast locations during some recent monitor sessions. Here is his field report he posted to the UDXF newsgroup yesterday (12/23/18)
"Checked a number of these 50bd/850 and 75bd/850 US Navy transmissions a couple of weeks ago using TDoA. I believe that the line-up looks something like this:
4005 Davidsonville, MD
4985 Davidsonville, MD
5340 Isabela, PR
6487 Davidsonville, MD
6831 Isabela, PR
7455 Isabela, PR
7597 Dixon, CA
7830 Isabela, PR
8093 Diego Garcia
8547 Diego Garcia
8676 Lualualei, HI
8694 Dixon, CA
9112 Lualualei, HI (seems to be occasional)
9830 Isabela, PR
10153 Isabela, PR
10430 Dixon, CA
11688 Isabela, PR
12015 Davidsonville, MD
12120 Isabela, PR
13229 Isabela, PR (only active briefly in November)
13870 Dixon, CA
14434 Lualualei, HI
15959 Davidsonville, MD
16047 Lualualei, HI (seems to be occasional)
16123 Isabela, PR
16268.5 Dixon, CA
18370 Guam (seems to be occasional)
18558 Lualualei, HI (seems to be occasional)
22471 Diego Garcia
22910 Diego Garcia
It’s been a while since I’ve heard NDT (Totsuka) which has been on 10830, 10827 & 14375 kHz at the beginning of the year."
Thanks for sharing Mike. I think I may have some ideas on what those occasional Stanag 4481 broadcasts are being used for. Further monitoring before I comment further.