Hi folks,
I'd like to share this video I recently put together that demonstrates how one can use Software Defined Radio to receive HF. I analyse a number of interesting/unusual signals (e.g. STANAG, DRM, OTH RADAR) by putting them through various pieces of software (e.g. HDSDR, GNU Radio, Sigmira).
HF and Software Defined Radio: HDSDR + USRP + GNU Radio + RFMap - YouTube
If you have any thoughts on the mystery signals I mention, please comment! (Some have already been revealed on the YouTube page...)
Hope you find it interesting!
Balint, do you participate in the IRC channel #wunclub on the Starchat server? If not you might find it interesting, and it would also answer a lot of your questions and many of these signals.
Very nice video, you obviously put some effort into it.
Some comments, I will put them here because there is not room enough on YouTube:
The “sweepers” at about the 01:15 mark in the video (and several other places) are indeed Ionosondes, also called Chirpsounders. You might want to research the AN/TRQ-35 or TRQ-35 sounder for details. Sweep rates of 100 kHz / sec are common. If you plot the time of the sounder at any frequency you can even correlate it back to the source. There used to be, not sure how active it still is, a Chirpsounder Yahoo group.
The signal at 01:42 is indeed HFDL, or HF-ACARS, as others have indicated. There are several pieces of software out there to decode it and pull the data.
Both radar Youtube videos you pull up at 03:00 are mine
The sweeps at 04:10 looks like CODAR, but the sample is too short to be sure, it could also be one of several sounders. Normally CODAR is not in that freq range.
The sweep at 04:40 is indeed CODAR.
The “blocks” at 04:53 are a sounder. The exact location and designation for this one has not been confirmed.
The sweeps at 06:25 are CODAR, under one of the channels of Chinese OTHR (I have seen up to 12 simultaneous channels of Chinese OTHR, in channel “pairs”
. The CW is unrelated to either.
The radar at 08:50 is a bit more iffy. It might be the radar you quote, associated with ACORN, using RFMap. It also might be, probably is in fact, the PLUTO II radar out of Akrotiri. The width (20 kHz), the sweep rate (50 Hz), and the sweep type (LFMCW) are all correct for PLUTO. Of course, these are also common techniques, so it could be any one of several radars. If it is always on that freq you noted it is probably the radar you have associated to it. However, PLUTO jumps in freq from time to time, keeping up with the MUF. It also has a several second period of dead carrier before the sweeps start. So, if you see that signal cease on one freq, jump to another a few seconds later, and start with several seconds of dead carrier before beginning the LFMCW sweeps, I think it would lend weight to it being PLUTO.
The non-linear sweepers you note at 10:50 in the video are a quandary. Several folks have been looking at them trying to narrow down what they might be, so far nothing concrete has come of it. What I can tell you, they are not people keying down drifty radios or radios that sweep on purpose, some of them have been noted with very specific cycle rates inconsistent with voice comms. They probably are not sounders of any type. And they have been around for decades, I remember hearing and tracking them in the late 60’s and early 70’s. One suggestion as to a source has to do with arc furnaces in foundries, but again that has not been confirmed in any way, it is just a thought.
The slow rate sweeper at 11:25 in the video is a sounder, it might be associated with JORN. If you pay close attention after it leaves one freq it steps up or down (one direction or the other, a given one always travels in one direction only) 1 to 2 MHz and sounds again. And then another 1 or 2 MHz and again, etc. The steps are not always even 1 or 2 MHz steps, but are often close to that size.
The signal at 11:54 is quite possibly an 8 tone Japanese mode. There are actually several possibilities as to what it might be, and without specifics of tone spacing and baud rates it is hard to narrow it down.
The multi speed sweeper at 15:40 is another sounder. Quite possibly associated with the same source as the one at 11:25, again, it might be related to JORN. Note that this sounder generally does 64 sweeps at each rate before stepping down to the next rate, it also often has 16 speed steps. And again it is common for this one to step up or down 1 MHz and sound again.
Hope some of that helps.
T!
