HFGCS Livestream - 241202B - Emergency Action Messages (EAMs)

buymeacoffee.c... ◆ / neetintel
If you are new to the HFGCS, EAMs, or this channel, this video I published in January is currently the best place to start. It gives a good overview of all these topics. • HFGCS SKYMASTER is com...
I run both these HFGCS livestreams and occasionally post both videos and tweets to KZbin and Twitter. If you're interested in the work I'm doing and are able to contribute, you can support this project via my Patreon and BuyMeACoffee. A portion of funds will be invested into equipment upgrades for improving future stream quality.
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Stream Info & FAQ:
I. Overview
This is a livestream of frequencies known to be used by the US military as part of their High Frequency Global Communications System (HFGCS), which is used by the US military to communicate with various assets (including nuclear-capable aircraft and submarines) in a variety of ways. One of the more interesting methods of communication that can be heard over the HFGCS is Emergency Action Messages (EAMs) and Force Direction Messages (FDMs).
II. Stream Source
All SDRs used in this stream are accessed using the global map of SDRs available on rx.linkfanel.net/
I endeavour to list the SDR on-screen (either location or URL). I used to endeavour to make sure I showed the url of the SDRs I streamed on all of my videos, but it's not always practical to show those in real-time. I do want to continue to endeavor to make this project in the spirit of open-source, so if you do need to know a stream address, etc. you can contact me by email (address in profile).
III. FAQ
𝑸. How long do streams last?
𝑨. As long as I don't forget to reset them, they run for about 12 hours - if they run much longer KZbin won't archive them. This is done manually because the streams run off of a 2009 iMac which can't support stream automation very well. (Streams will continue to run off this device until it burns out or I find a good deal on a newer model, with funds from the above used to subsidize the purchase.)
𝑸. What's an EAM?
𝑨. From a recent document published by the Department of Defense; "Emergency Action Messages (EAMs) are highly structured, authenticated messages primarily used in the command and control of nuclear forces. They are disseminated over numerous survivable and non-survivable communication systems including terrestrial and space systems."
The typical EAM is 30 characters, but it can vary. Some messages are slightly shorter, at only 27 characters. As well, sometimes messages over 200 characters long are broadcast*.
𝑸. What's an FDM?
𝑨. Some of what we refer to as 'EAMs' are actually FDMs. It seems likely that the first 2 characters of a message distinguish an EAM from an FDM.
𝑸. Why do you occasionally stream from antennas in Europe? Wouldn't it make more sense to only stream from SDRs in North America?
𝑨. Yes, but the impact isn't as great as you might think. The HFGCS has ground stations across the world, and these stations have a relay system set up so that all ground stations simulcast the same messages at the same time. UTwente WebSDR's antenna is located in the Netherlands, and most likely picking up these broadcasts from (at least) HFGCS transmitters at RAF Croughton (UK) and/or NAS Sigonella (Italy). As far as ground station transmissions go, there's essentially no difference.
However, there are also broadcasts by airborne "relay stations", which are transmitted by (at least) E6s flying about the US. While "relay station" is my own terminology as far as I'm aware and the actual term is probably TACAMO**, "relay station" captures something the more obtuse term doesn't - the majority of messages broadcast by these aircraft are repeats of those broadcast by ground stations. SDRs in Europe won't pick them up.
𝑸. How many structured messages are broadcast on any given day?
𝑨. The 'typical' amount of daily messages is around 10-15, but the range is quite wide;
Occasionally, there are days with 0 messages; recent examples include Sept 30 2023, Nov 23 2023. This will often line up with holidays - Nov 23 2023 was Thanksgiving.
Alternatively, there can be many more messages; Nov 30 2022 had over 50 messages, Sept 5 2023 had over 40. Attempts made to correlate these days with real-world events are usually only circumstantial at best.
𝑸. Are these messages cause for concern?
𝑨. No. (Probably not.)
𝑸. How can I contact you directly?
𝑨. Under this channel's main page, my email is available by clicking 'and 3 more links'. I don't regularly check that account, so if you need to contact me directly and also need prompt response you can either remind me to check my mail in a video comment or over Twitter.
Recordings are available; see • HFGCS Individual Messa...
** en.wikipedia.o...