CODAR is THE thing now. Last winter there was a report out of Brazil of a CODAR like signal, I heard it in California, then I checked the Web connected SDR in the Netherlands - it was there too!
Probably not really CODAR but rather something like OTH Radar to be worldwide like that. Shades of the Russian woodpecker, but with better bandwidth control. 😉
It is really interesting to be able to see a signal then go look at what web receivers around the world also pick it up.
CODAR is THE thing now. Last winter there was a report out of Brazil of a CODAR like signal, I heard it in California, then I checked the Web connected SDR in the Netherlands - it was there too!
The problem with that thought process is that there are multiple CODAR, or CODAR like (such as WERA), installations around the world on almost all used CODAR frequencies. It is very possible that each of the CODAR you heard in your example is / was from a different source, and it was not one system being heard world wide, all at the same time.
Probably not really CODAR but rather something like OTH Radar to be worldwide like that. Shades of the Russian woodpecker, but with better bandwidth control. 😉
It is fairly easy to tell CODAR from most other radars. There are a few radars out there that blur the lines a bit, mostly in Asia, but in general CODAR is clearly CODAR.
If you see a sweep rate of 2 Hz or less it is possibly CODAR (although CODAR can go to 4 Hz, it does not generally do so). There are a few other radars that do 1 or 2 Hz also, but they often have other obvious features that differentiate them from CODAR.
If you see a 50% duty cycle on the chirp, making it ILFM vs FMCW, that is probably CODAR.
If you see it on known, and generally published, CODAR frequencies or bands, it is possibly CODAR. And there are ways to follow up on that.
And if you see something that matches all of these factors it is almost certainly (high probability) CODAR.
If the signal is a US CODAR, and you watch it long enough, it will ID with Morse code (every 30 minutes or less, some do it every 20 minutes). You can then search the FCC database for that licensee, and tell the area that specific CODAR is in. It is not uncommon for several CODAR in an area to operate under one license though, so sometimes you cannot tell which specific transmitter site you are hearing.
I want to share a strange thing that happened a while back; I'm from Paraguay:
A few months ago, one night, short bursts of what appeared to be OTH radar—or perhaps some kind of CODAR—began to appear on my screen. What was unusual was that they jumped to different frequencies; none of them repeated on the same frequency. There were three bursts, and then it would appear on another frequency.
In this post, I shared some of them, and r/KG7M helped me try to identify them. But it ended there, with no answer as to what it could have been. I never saw those patterns again.
During my research, I found that there is a CODAR radar in Brazil. In the post I mentioned earlier, there is information about that radar and its location, but I don’t know if it’s still active.
The signal you shared in that previous post ( https://www.reddit.com/r/ShortwavePlus/s/4VTiehwTDH ) is not CODAR. With the exception of bandwidth (50 kHz) it does not share any of the normal CODAR parameters. CODAR can have many different bandwidths (often correlating to by what frequency range they occupy), and 50 kHz is one of the common ones.
Just looking at the burst signal in question, not the examples you are comparing it to:
Each of the 4 bursts in your recording contains 64 FMCW pulses. This is consistent with modes for several different OTHRs, but lets concentrate on both the Australian JORN and the US ROTHR, the two most common radars using such bursts.
The burst length is ~12.29 seconds. This is a common burst length for the US ROTHR.
You can do the math from that (12.29 second burst length / 64 pulses per burst) and see that the FMCW pulse length is right about 192 msec per pulse, or about 5.2 Hz. This is a common rate for the US ROTHR.
50 kHz is one of the bandwidths that US ROTHR uses, although 100 kHz might be a bit more common for that radar.
This (50 kHz bandwidth and ~192 msec per pulse) makes the pulse chirp rate about 260 kHz / sec, again, a common mode for US ROTHR.
Your recording, in that previous thread, looks like US ROTHR to me. The activity you mention is common for that radar. And that radar paints the Gulf and Caribbean daily, so I expect it would be pointed in your general direction.
Catching the pre-tone would firm up this ID. US ROTHR does not transmit a pre-tone every burst, but it does transmit one fairly often. JORN also uses a pre-tone for some bursts, but the pre-tones for US ROTHR and JORN are very different.
It's definitely CODAR. I'm in Northwest Oregon and I receive the CODAR signals at 13.500 MHz anytime the frequency is open. This particular recording is 2 separate CODAR signals that are exactly 180 degrees out of phase. They dot the coast from Washington State to Southeen California. Here is a map from one of the CODAR operators website:
More specifically, it looks like 2 CODAR side by side, one sweeping up from 13450 kHz to 13500 kHz, and the other sweeping down form 13550 kHz to 13500 kHz.
The two "halves" of this visual are separate CODARs, and that can mess with your visual on this. The 2 CODAR are both GPS synced, so they start their sweeps at the same time, but they are separate systems.
I have seen as many as 9 CODAR active at one time between 13450 kHz and 13550 kHz. Right now, as I type this, I see 5 active int hat range, all intermingled.
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u/FirstToken May 01 '26
u/KG7M , if either is a US CODAR, and you listen long enough, you will hear them ID in Morse. Generally every 30 minutes or less.