HFU HF Underground
General Category => General Radio Discussion => Topic started by: Oliver on August 21, 2018, 1039 UTC
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A very interesting investigation done by Alex (aka ulx2).
http://ulx2.byethost24.com/blog/2018/08/21/who-makes-the-qrm-to-pirate-stations-on-48-mb/
I hope this post is ok per our TDoA guide lines.
Thanks to uk dxer for sharing via Twitter.
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Thanks for sharing, very interesting. We've done this on this side of the pond as well, finding the locations of the Link-11 that hangs out around 6940, and the wide band digital signal overtop 6925, presumably one of the high speed financial trading firms near Chicago.
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TDoA would be interesting for Spy Number Stations.
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Link appears to be broken?
+-RH
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Impressive work.
It just dawned on me there should be a global log of all tdoa results so we have some idea as to where everything's coming from.
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Had to try 2-3 times before the link worked. Not sure if that was a local connection issue or something else.
On another note, isn't 6200 kHz to 6525 kHz the 6 MHz marine mobile band for USB voice and various data modes? Yes, 5900 kHz to 6200 kHz is the busy 49 meter broadcast band so it makes sense for Europirates to hang out right above the band edge...
I know the 6200 to 6400 kHz range is popular for pirates regardless...not to mention North Korean shortwave broadcasts on 6400 kHz! Either way, this is some interesting reading.
Would be interesting to see it done for the 6765 to 7000 kHz range for 43 meters and North American / South American pirates (and the pescadores/freebanders/radiotelephone link systems carrying Spanish and Portuguese language traffic - not to mention the New England fishermen often heard in this area...). I know the big ones (the double side band Link-11 signal that pops up around 6940 kHz and the wideband ute around 6925 kHz, as Chris mentioned, have already been "TDoA'ed" but there's a lot of other mystery stuff on 43 meters that I wouldn't mind knowing where it's coming from (aside from pirate broadcasters, of course ;))
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Impressive work.
Agreed.
It can take several tries to get meaningful TDoA results for just one signal, perhaps another round just to verify it and many more if you have absolutely zero idea where it originates from. Then when you consider all the other things that go wrong, e.g., that one critical receiver that you had planned on using to form a good triangle around where you think the TX is located all the sudden not getting any recent GPS readings and thus becomes unusable (a frequent occurrence) or that receiver all the sudden dropping off the internet, and so on, this collection of TDoA info probably took a number of hours, even if it was "multithreaded".
I was similarly curious about some of the signals in the 48 meter band and can verify that I received similar results for those that I tried.