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Author Topic: Numbers on 6.739USB at 23:21 UTC, Feb 10. 2018  (Read 867 times)

Offline tonehammer

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Numbers on 6.739USB at 23:21 UTC, Feb 10. 2018
« on: February 10, 2018, 2326 UTC »
Computer generated voice numbers broadcast .. lasted only about 3 minutes. I just happend to spot the modulation on an SDR.
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Offline tonehammer

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Re: Numbers on 6.739USB at 23:21 UTC, Feb 10. 2018
« Reply #1 on: February 10, 2018, 2348 UTC »
Again at 2346, ended at 2349.
Location:  NW North Carolina mountains
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Offline tonehammer

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Re: Numbers on 6.739USB at 23:21 UTC, Feb 10. 2018
« Reply #2 on: February 11, 2018, 0022 UTC »
Again at 0020 until 0022 weaker this time.
Ended with "this is rebetnit ??, out"

Again at 0025 until 0027
Same sign out.

Again at 0034 until 0036
The voice had an echo, so every letter/number was duplicated by the echo.
Same sign out.
« Last Edit: February 11, 2018, 0036 UTC by tonehammer »
Location:  NW North Carolina mountains
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Also: eton E1 / Satellit 650 / Satellit 800 / Tecsun PL880 / many others
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Offline fpeconsultant

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Re: Numbers on 6.739USB at 23:21 UTC, Feb 10. 2018
« Reply #3 on: February 11, 2018, 0203 UTC »
EAM??
Near Chicago, IL USA.  Drake R8, Ten-Tec RX340, JRC NRD545, Watkins Johnson HF-1000, Wellbrook loop at 28', 40m inverted vee.  Please QSL to fpeconsultant@aol.com thanks.

Offline Traveling Wave

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Re: Numbers on 6.739USB at 23:21 UTC, Feb 10. 2018
« Reply #4 on: February 11, 2018, 0455 UTC »
Yes, 6739 USB is an EAM frequency.
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Offline fpeconsultant

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Re: Numbers on 6.739USB at 23:21 UTC, Feb 10. 2018
« Reply #5 on: February 11, 2018, 1310 UTC »
The "echo" of the voice gave it away!
Near Chicago, IL USA.  Drake R8, Ten-Tec RX340, JRC NRD545, Watkins Johnson HF-1000, Wellbrook loop at 28', 40m inverted vee.  Please QSL to fpeconsultant@aol.com thanks.

Offline Token

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Re: Numbers on 6.739USB at 23:21 UTC, Feb 10. 2018
« Reply #6 on: February 11, 2018, 1335 UTC »
Just to keep things straight I moved this thread from Spy Numbers to Utility.  These HF-GCS transmissions are not generally considered numbers transmissions, although they definitely do send coded messages in letters and numbers.  Unlike spy numbers transmissions these messages are generally just grouped with other military coded transmissions.

To the OP, these are not computer generated voices, this is a human, often a young airmen, setting at a mic reciting these messages.  The type of message you heard is referred to as an "EAM", or "Emergency Action Message".  This is one of several formats of message you will hear on this network.  The most commonly used frequencies are 4724, 6712, 6739, 8992, 11175, 13200, and 15016 kHz, all in USB mode.

Most messages are simulcast on all of those frequencies at the same time, and by up to 13 different ground stations at the same time.  These multiple ground stations all sending the same message at the same time are what causes the "echo" sound you heard.  On top of normal propagation delay, this would cause a relatively small echo to be heard, they use a VOIP like backbone to transport the audio to each node, and there is some variable network latency, this network latency causes the sometimes quite deep echo that is frequently heard.

If you want to research this network do a search on HF-GCS, High Frequency Global Communications System.  Just be aware that many details on the network are classified, and so in addition to the good information to be found there is also some pretty bad stuff out there, incorrect and misleading information, floating around out there.  For example, if you read anything about the number of "Skykings" said in a row (a "Skyking" is another type of message heard on this network) relating to message importance, ignore it.  That started as a joke in chat, and became internet "fact", now with charts and web sites supporting and repeating it.

T!
« Last Edit: February 13, 2018, 1207 UTC by Token »
T!
Mojave Desert, California USA

Offline Token

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Re: Numbers on 6.739USB at 23:21 UTC, Feb 10. 2018
« Reply #7 on: February 11, 2018, 1427 UTC »
Again at 0020 until 0022 weaker this time.
Ended with "this is rebetnit ??, out"

Again at 0025 until 0027
Same sign out.

Again at 0034 until 0036
The voice had an echo, so every letter/number was duplicated by the echo.
Same sign out.

The callsign used for all three of these transmissions was "Revetment".

The third one you have listed here was for a specific station, unlike the other two, and started with "for Abolish".

T!
T!
Mojave Desert, California USA

Offline R4002

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Re: Numbers on 6.739USB at 23:21 UTC, Feb 10. 2018
« Reply #8 on: February 11, 2018, 1614 UTC »
The USAF transmissions can be pretty nice indicators of propagation conditions.  I didn't think about the variable latency part of the equation until Token mentioned it.   I've heard transmissions on 6712 USB and 6739 USB with echoes that almost were interfering with each other.    At that point, 6739 kHz USB was a lot stronger than 6712 kHz USB.

The HF-GCS system is one of the more popular utility monitoring targets...even though they're using one time pads so the content of the message is simply unknown.  More can be gleaned by traffic analysis (how often transmissions are made) but of course, that's something the US military knows as well and I'm sure they account for.

Regardless, these transmissions still fascinate me after all the years I've been listening to the radio.
U.S. Eastern Seaboard, various HF/VHF/UHF radios

Offline fpeconsultant

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Re: Numbers on 6.739USB at 23:21 UTC, Feb 10. 2018
« Reply #9 on: February 11, 2018, 1835 UTC »
Yes I agree - I enjoy chasing them around the dial.
FPE
Near Chicago, IL USA.  Drake R8, Ten-Tec RX340, JRC NRD545, Watkins Johnson HF-1000, Wellbrook loop at 28', 40m inverted vee.  Please QSL to fpeconsultant@aol.com thanks.

Offline MDK2

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Re: Numbers on 6.739USB at 23:21 UTC, Feb 10. 2018
« Reply #10 on: February 11, 2018, 1918 UTC »
I was hearing them not long ago on 15016 and 11175, but strangely not 13200, c. 1830 UTC.
« Last Edit: February 11, 2018, 2335 UTC by MDK2 »
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Offline Token

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Re: Numbers on 6.739USB at 23:21 UTC, Feb 10. 2018
« Reply #11 on: February 11, 2018, 2308 UTC »
I was hearing them not long ago on 15016 and 11735, but strangely not 13200, c. 1830 UTC.

It is probable it was just a propagation issue, but there are a few other potential reasons for this.

While the operators may select all frequencies and all transmitter sites, they do not have to.  So possibly the transmitter location or locations you were hearing did not have 13200 kHz selected.

Airborne sources tend to use fewer frequencies.  It has never been confirmed but it makes sense that an airborne command post could have access to the entire network, just as the control ground stations do.  But quite often you will hear an airborne source that is direct, i.e. it is transmitting on multiple frequencies but is NOT using the 13 ground locations, the transmission is just from the platform.  In that case I have often seen them on a more limited frequency set, like maybe only 4 frequencies at one time.

T!
T!
Mojave Desert, California USA

Offline tonehammer

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Re: Numbers on 6.739USB at 23:21 UTC, Feb 10. 2018
« Reply #12 on: February 13, 2018, 0211 UTC »
I appreciate your efforts to provide all that info T!
Location:  NW North Carolina mountains
Primary:  SDRplay RSP2 with Dipole cut for 6.800mhz
Also: eton E1 / Satellit 650 / Satellit 800 / Tecsun PL880 / many others
eQSL appreciated: hammertoneamps@gmail.com