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Post by Shazepe III on Jan 7, 2014 2:23:53 GMT
Link to my recording, RW has a longer one in AM as well ehhh video says USB but I was in LSB mode, just to clarify that 8000 kHz also has a very faint but noticeable carrier there that never went away EDIT: Also the image someone else grabbed: i.imgur.com/ayXBIsw.jpg
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Post by RW Observer on Jan 7, 2014 2:30:17 GMT
Yes indeed, here is a link to my 17 minute recording. The majority of the broadcast is recorded is in AM, however it does switch to usb for the final minutes. Towards the end the broadcast stops but commences again.
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iarat
New Member
Posts: 5
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Post by iarat on Jan 7, 2014 3:29:58 GMT
Hey guys, I was listening to the XDE on 8000 AM off and on for most of the day until around 20:00 UTC. What time did it finally stop broadcasting?
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Post by mattomanx77 on Jan 7, 2014 6:09:34 GMT
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Post by Echo One on Jan 7, 2014 12:26:01 GMT
It has been suggested that it is some sort of Earth-Space research thingiemabob. It has also been suggested it might have something to do with the NSA. I'm going with the research angle myself
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Deleted
Deleted Member
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Post by Deleted on Jan 7, 2014 16:04:06 GMT
I suggest it as Over the horizon radar....
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Post by zabastov on Jan 7, 2014 17:06:14 GMT
We will likely never be able to prove what this is, but we can make some educated guesses.
What I am fairly sure it is not, is a radar. However, mistaking this signal for radar is not a new thing, it seems like every swept signal you find on HF gets called a radar at one time or another by someone. This same signal, or one very much like it, was reported in 2012 and 2013 on various frequencies , including 7001.5 and 12000 kHz. If you search for a pdf called “Radar systems on Shortwave”, by DK2OM (there are 2 versions of this paper, 2012 and 2013), you will see he mentions (in the Israel section) something that is probably this signal and ask the question of if it could be a new radar. However, he only asks the question, he never states it is an OTHR.
OK, why is it unlikely to be a radar?
First, look at the waveform itself. It consist of a triangle wave swept signal (DK2OM calls it a sawtooth wave, but it is in fact triangle, even in his images). You will find no current or past HF radar using a triangle wave sweep. This does not mean that a radar could not use such a sweep, but the reason it is generally not used is there are several shortcomings to such a waveform. To go into detail for all the problems with such a waveform would require a fairly lengthy tome, but the biggest single reason is that at the change of direction points (both high and low frequency ends) Doppler value / returns from the target are lost or become ambiguous. In affect you throw away some of your target return energy. Depending on the sweep rate and the radial velocity of the target this can end up being a large portion of all of your returns. This is why most FMCW radars do, in fact, use a real sawtooth wave sweep, with a sawtooth this problem does not exist.
Second, look at the audio tone of the sweep. Particularly pay attention to the tone at the low audio frequency end. The tone has a rough or slightly raspy quality to it. This is because the change rate of the audio tone is not smooth, but rather appears to be stepped. If it is indeed stepped, even micro stepped, the energy is near useless for FMCW radar applications….it is NOT FMCW at that point. For processing purposes it becomes a series of pulses, each on a slightly different frequency, and it has none of the advantages of an FMCW radar, and all of the disadvantages of a simple pulsed radar, plus the added complexity of the stepped frequency processing.
Third, and last for now, although there are several more reasons that could be brought up, look at the transmission itself, particularly the screen shot of the waterfall. For at least part of the time, if not all of the time, it was a full AM signal consisting of LSB, USB, and full carrier. The fact that the USB and LSB images and information appear to be identical indicates it is in fact DSB (Double Sideband) with full carrier, or good old AM, just like most shortwave and mediumwave broadcasters use. No radars use a waveform like this. It is extremely wasteful of energy (more energy is in the carrier than in the intelligence) and has no positive aspects to support its use in a radar.
So, if not a radar, what is it? Like I said, we may never be able to prove or disprove what it might or might not be. However, my bet is that it is a triangle wave swept audio test tone being injected into a transmit facility to test the audio modulator or transmitter itself. Such a signal is often useful to determine the audio passband of the transmitter. This action is called, simply enough, “sweeping” the passband. Looking closely at this signal you will see it is a triangle wave with about 5 kHz of sweep width occurring every 6 seconds. I have used such signals myself to test transmitters.
Z!
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Post by victor on Jan 7, 2014 18:08:04 GMT
I completely agree with Zabastov! About at 14.00gmt I made some *serious* measurement on the XDE [on/off random]: level was ~ 45 dbµV on 30m random wire antenna (site in NE Italy)... pretty strong! Interesting is the "bubbling" modulation under the sweep. There I need more time to dig into ;-) Just a question remain by my side: "IF we are testing a new transmitting site, WHY we need to send the same test signal (only USB) also on 3630.8 ? Another possibility: this is a "chirped" transmission and the other emission is needed to sync LO and reconstruct the info (the bubbling???) .... To Be Continued
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Maris
Junior Member
Posts: 41
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Post by Maris on Jan 8, 2014 21:45:16 GMT
On July 2013 on 7000 kHz a similar signal and also on August
The 8000 kHz signal on the night of January 8 with my main home receiver
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Post by numberstationsgal on Jan 9, 2014 1:24:24 GMT
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Post by RW Observer on Feb 3, 2014 21:16:41 GMT
Heard this signal on 4596 kHz, still broadcasting as of 2115z
It certainly does sound similar to XDE, it could possibly be it on another frequency.
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Post by Weighted_Cube (Ali) on Feb 3, 2014 21:56:22 GMT
Its the same thing! XDE IS ALIVE!!!
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