Wednesday, November 20, 2013

Coast Guard Data Bursts?

I have recently seen complaints from multiple locations about hearing some sort of digital noise or interference on the Coast Guard primary air operations frequency of 345.0 MHz. I thought I was not hearing it myself, but I set up one of my tunable wide-band receivers on this frequency and did hear it clearly when I opened the receiver squelch all the way.

What I am hearing is a series of short bursts  of noise, almost like a burst of machine gun fire. The length seems to be from 4 to 6 "bursts" in a group, although some have been two groups of 4 or more in a row. I can also heard weaker stations followed by bursts from stronger stations. Sometimes the bursts are at a moderate tempo, and some seem to be very rapid compared to others.

Here are some short clips of what I heard. Turn the volume up when watching these:

video

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At first I wasn't sure if these noises were intentional or just some form of interference, but after  hearing them and listening to the patterns, I am guessing they are intentional usage of the frequency by the Coast Guard. As to what this is used for and why they are using this frequency remains a mystery. Anyone want to guess at what's going on here?

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