UNID signal, sweep noise w/ beep every second, 13560 khz; 1918 UTC 5/27

[BoomboxDX]

I tuned through the 13 mhz region to hear this beep beep beep, very weak, about every second, with a weird sweeping, white noise over the top of it.  No CW IDs or anything, just 'beep beep beep'.

Any ideas what this could be?  The one second beeps were gone during recheck at 2005 UTC.  Is this some sort of UTE or radar?  

PS, sorry if this is in the wrong section, wasn't sure if I should put it here, 'utility', or in 'other'.

[Token]

Probably going to need either a little more detail, or a recording, to make much out of this.

You say “13 MHz region”, but that covers a lot of ground.  In that range are multiple CODARs and that could be the source of your beep every second or so.  These could also be the source of your “sweeping” sounds.  However, there are also single letter beacons, digital transmissions, RFID systems, frequency hopping sounders and radars, etc, all might fit with what you are describing.

T!

[BoomboxDX]

The 'beep beep beep' zeroed at 13560 khz. 

The sweep noise appeared there, and also appeared below 13560 (in my logbook I also noted the sweeper noise appearing around 13455 khz).  The sweeper noise might have been those CODAR signals I've read about, and I've think I've heard those same sweeper noises in other areas of the shortwave spectrum.

The single beep I haven't heard before.  And it seemed to fade and strengthen like an HF signal does, so I don't think it was locally generated.

Thanks for the response.  I'm definitely going to keep my ear on the frequency and see if the 'beep' reappears.

[Token]

Was the sweeper a regular, rythmic, sound (sweep, sweep, sweep, with a regular interval), or was it irregular?  If regular it was probably CODAR, and there are a several in that frequency range (from about 13365 to about 13580 kHz).  If the sweeper was irregular then I probably know the signal you are talking about, I have heard it, but have no idea what it is.  No one else I have talked to is sure what it is either, but there have been several suggestions.

A video of a CODAR (not the same freq, but they are similar):
http://www.youtube.com/watch?v=pW9dK8J5jRA


A screen shot of the irregular sweeper, both on a local receiver and on a remote receiver, in this case the remote was in Washington state:


T!

[BoomboxDX]

RE: the CODAR: It was the regular sounding sweeper -- regular intervals.

Haven't heard the beeper since, but have heard the sweeper.

A question about the CODAR use: where do the actual transmissions come from?  Is there a list somewhere?  Can't seem to find one.

[Token]

There are hundreds of locations around the World with CODAR, it is very, very, difficult to determine where any particular one you are hearing is coming from.  In some cases you can look at licensing and get an indication that might be what you are hearing, but only might be.  There is no one list of all CODAR, although you can often find lists of CODAR associated with specific universities and research coordinators.  In many cases the data from these systems can be accessed online.

Pretty much any place with a coastline might have CODAR these days, and CODAR is relatively low power, but because of the nature of HF propagation you might hear many CODAR even if you are far from any coast.

T!

[BoomboxDX]

I heard the beeper alone on the 13560 khz (no sweeper noise on top of it), 0811 UTC, 6/1.  

Other times I've checked recently it's either a single CODAR, a single CODAR with another just lower in frequency, with no beep.

Below 13560, I've heard what sounded like several CODARs ranging between 13410 and 13560.  It's hard to tell where one starts, and the next one stops (no SDR here).

RE: CODAR bandwidth -- from looking at the CODAR SDR shot on Wikipedia (taken by a ham -- it looks like it was a CODAR intrusion into the 20 meter ham band) it appears that CODAR sweeps are about 20 khz wide?  Is this pretty standard for most CODARS?

[Token]

RE: CODAR bandwidth -- from looking at the CODAR SDR shot on Wikipedia (taken by a ham -- it looks like it was a CODAR intrusion into the 20 meter ham band) it appears that CODAR sweeps are about 20 khz wide?  Is this pretty standard for most CODARS?

Sorry I missed this before.

There is no “standard” swept bandwidth for CODAR.  There are some general guidelines as to what you might expect to see.  In general the lower the frequency of operation the narrower the swept bandwidth.  I have seen CODAR use anything from 12 kHz to over 200 kHz and I have no idea what their real limitations are.

Around the 5 MHz region I typically see about 26 kHz, up around 13 MHz I typically see about 50 MHz., and up around 25 MHz I often see 100 kHz.  On the other hand, I have also seen 24 kHz in the 25 MHz area, so as I said the “narrower at lower freqs” is just a rough guideline.

Sweep rates are generally between 0.5 and 4 sweeps per second.  Chirp rate (pulse compression) will be sweep rate times bandwidth.

Many CODAR run 24 hours a day, others cycle on and off at different times.

Some pictures of various CODAR:

This is two interleaved CODAR centered on 4550 kHz.  They are both the same width and they stay in sync (probably GPS timing based), this way they do not interfere with each other despite occupying the same frequency range.  The width measures out at about 26 kHz.


The above 2 CODAR can be seen operating here:
http://www.youtube.com/watch?v=8OF-yhrtqKo

This is a CODAR centered on 12190 kHz.  It is about 52 kHz wide.  Another can be seen to the left of the one in question, it is also roughly 52 kHz wide.


And last is a CODAR centered on 13500 kHz, with a width of about 150 kHz.


CODAR, ionospheric sounders, and “real” radar (radars looking for man made and moving targets, such as ships and aircraft, or rapidly changing natural features, such as weather) are all radar and often use identical techniques.  But I typically break them out into CODAR, sounders, and radar, and speak about them as if they are not all “radar” to reduce confusion.

CODAR sweep relatively wide (compared to “real” radars) and relatively slowly because their target set is slow moving and such a technique lowers equipment cost.  Sounders typically either sweep or sample (two different things) even more slowly than CODAR because the sounders target set changes even more slowly than a CODARs target set.

On one hand the sweep rate determines maximum unambiguous range for an unencoded FMCW waveform when applied to a radar or CODAR.  The slower the sweep rate, for a given swept width, of an FMCW radar the greater the possible unambiguous range.  However, a sweep rate of about 7 times a second yields a possible unambiguous range that could stretch all the way around the World.  So the typical CODAR sweep rate of 1 sweep per second would yield a range of over 7 times the distance around the World, but CODAR typically looks at data at 300 km or closer.  In other words the sweep rate of the CODAR, unlike “real” radars, has nothing to do with maximum unencoded and unambiguous range, and more to do with target set velocity and cost of the technology.

“Real” radars sweep faster because they are designed for a realistic maximum range, based on detection thresholds (how small a target RCS, Radar Cross Section, that can be tracked at a given range, a complex relationship, search “radar range equation” for an introduction), technology, and probable propagation in the frequency range of the hardware.  If the desired maximum range is 6000 km than a sweep rate of 25 Hz would be used (and 50 Hz yields a maximum of 3000 km).  Of course, a lower sweep rate (say 10 Hz) would also yield at least that range (10 Hz yielding a max possible range of 15000 km), but at the cost of illuminating the target less often, lowering the probability of detection.

Several other factors define the width swept and chirp rate (pulse compression), based on the performance of the desired target set.  But, this post is long enough already ;-)

T!

[BoomboxDX]

Many thanks for the info, Token.  It's very helpful.  I used to just ignore the CODARs when tuning the bands, now I log them down (if I can tell them apart).  Mainly what the frequency range is, and how many of them I think I'm hearing...

I with there were a list of them somewhere.  I tried entering various frequencies on the FCC database, came up with nothing.... :-(