HFU HF Underground
Loggings => HF Mystery Signals => Topic started by: alleycat on January 24, 2021, 0134 UTC
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Are there other LINK- signals besides LINK-11? I hear a 2.8 kHz-wide signal booming in perennially on 6942 kHz (upstate NY, U.S.) that sounds like LINK-11, but the pulses are very regular. The example on SigIDWiki has long bursts between regular short pulses, while the recording on FirstToken's YouTube channel at https://www.youtube.com/watch?v=__-rtLRQUhg (https://www.youtube.com/watch?v=__-rtLRQUhg) is characterized by a 'lilting' pulse. An audio example of what I'm hearing is posted to https://www.lutins.org/temp/6944_kHz.mp3 (https://www.lutins.org/temp/6944_kHz.mp3), with a waterfall capture at https://www.lutins.org/temp/6944_kHz.jpg (https://www.lutins.org/temp/6944_kHz.jpg). Thanks for enlightening me!
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That is still Link-11. In this case it is Link-11 CLEW on 6942 kHz USB.
There are two kinds of Link-11, Link-11 CLEW and Link-11 SLEW, and they do sound different from each other. In addition to the two types, Link-11 can be variable in sound, it is not always the same. This variability depends on several things, for example how many nodes are in the network, and what part of the network you are hearing.
For Link-11 CLEW (the kind in your picture and audio example) the bursts themselves always contain certain aspects that are unchanging. When properly tuned (6942 kHz USB in this case) there are three major portions of the signal that can help in IDing. There is the Doppler Tone, which will be at 605 Hz audio, there is the Synchronization pulse, which will be at 2915 Hz audio, and there 14 channels of data between those.
Link-11 SLEW is somewhat similar in pulsing nature, but a totally different structure and sound.
T!
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Anyone capture any Link 22 Tactical Digital Information Link (TADIL) audio samples or know of any active link 22 frequencies? Link 22 (STANAG 5522) is the next generation of Link 11 (MIL-STD-6011 / STANAG 5511).
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Anyone capture any Link 22 Tactical Digital Information Link (TADIL) audio samples or know of any active link 22 frequencies? Link 22 (STANAG 5522) is the next generation of Link 11 (MIL-STD-6011 / STANAG 5511).
I have not knowingly heard, nor have I talked with anyone that has knowingly heard, Link-22. But, Link-22 is in late testing, and if budget reports are to be believed has been on several platforms and vessels for some time during test and evaluation. That may mean it has been heard and no one realized what they were hearing.
Reading the description it sounds like it may be similar to several modes already in use. Could it already be out there and it is being confused for one of the other wide'ish PSK data modes? Might some of the traffic that gets off handedly blamed on something else be it?
The other issue is that Link-22 is supposed to be backwards compatible with Link-11. I assume that during such operation it will be indistinguishable or hard to tell from Link-11. I think it is very possible people have heard Link-22 hardware in Link-11 mode.
T!