4200-4250khz, strange pulsing signal

[bob-the-scanner-man]

I've been picking up a strange pulsating sort of noise lately in Central AL. It starts around 4200khz and goes up to 4250khz. When I get to 4230khz I can hear what sounds like two of these signals transmitting at once for a sort of "echo". Strangely, as I turn the dial and go up or down in frequency it seems to have no effect on the signal. It literally stays the same between each frequency.

I don't have a video of it that I made myself, but I did find this video which shows the exact same thing only on different frequencies.
Odd pulsing sound 12100-12200 kHz - YouTube

Times received:
1/11/2012 @ 07:30 UTC
1/12/2012 @ 01:00 UTC
Central AL
Radioshack DX-392

Hope someone can shed some light on this!

 

[bryan_herbert]

CODAR ocean sensors

:: CODAR Ocean Sensors - Technical Support ::

 

[bob-the-scanner-man]

Thanks for clearing that up for me! I figured it was probably some type of radar but I wasn't entirely sure.

Any idea on the location of the transmitter?

 

[Token]

Thanks for clearing that up for me! I figured it was probably some type of radar but I wasn't entirely sure.

Any idea on the location of the transmitter?

There are literally dozens of possibilities for location. I rather doubt you will ever be able to say with any certainty which one specifically you are hearing unless you are willing to track it down and find it using RFDF techniques. At any one time here I can often receive about a dozen CODARs, and under good conditions I have seen as many as 30 all at the same time across the entire HF spectrum. I have seen as many as 4 CODARs using the exact same frequency range (same start and stop freqs). Because they are GPS synced and the nature of IFMCW Doppler radar they can afford to do so with minimal interference.

Suffice to say, the one you are hearing is on a coast someplace

If you really want to try and narrow it down you can search the FCC database. This can remove possibilities and in the case of seldom used frequency ranges narrow the likely sources. But you are not going to find a source that says "4200 - 4250 is assigned to only this one CODAR".

T!

(edit) On a whim I decided to see how many I could find i the middle of the day, right now. I have 2 interleaved from 4537 to 4563, 1 from 4772 to 4798, 1 from 5223 to 5248, 1 from 11985 to 12040, 1 from 12142 to 12177, 1 from 13426 to 13476, 1 from 13455 to 13505, 1 from 13552 to 13592 and 1 from 13974 to 13971. Only 10 right now, a bit low count for average. I often see them higher in freq during the day, but not today, propagation is down a bit. Tonight the lower freqs will waken up, and many, many more will be active.