wrote:

Well, it's a mystery to me at least.

After about a decade of basically doing no SWLing at all (due to
living in increasingly electrically noisy urban environments that took
most of the fun out of the hobby), I've started taking my Lowe HF-150
along on camping trips. These are a wonderful way to escape manmade
noise, by the way; nothing beats being able to put miles between you
and the nearest computer or touch lamp. But I digress.

I've noticed a strange new data wideband format. New to me that is,
it's obviously something that came on the scene in the last decade or
so. It has sort of a "boing, boing, boing" sound to it when tuned in
USB mode. The sound varies somewhat as time passes and as one tunes
through the ranges being used. And it is WIDE -- like 30 kHz or so
wide.

On 13 August between 0340 and 0400 UTC, I noticed such signals
occupying the following frequency ranges: 5218 - 5249, 4640 - 4678,
and 4390 - 4448. The latter was interfering with a Coast Guard marine
weather transmission on 4405 kHz. Listening location was in the
Cascade Mountains east of Mt. Hood, OR.

I still don't have an easy way to make recordings while camping, so
unfortunately I have no recordings of it to share. When I do get
around to making a recording, I'll probably give samples to my
musically-inclined friends for sampling and use in compositions --
it's a fascinating sound, whatever it is.

Anyone have an idea what this is? I've tried doing a little Googling,
but to no avail. The signals seem to occupy a variety of frequency
allocation ranges (often overlapping two of them; see
http://www.rdrop.com/~billmc/freq_list.4 ). I've drawn a complete
blank in my own efforts to solve the mystery; hence this post.

At least part of what you are hearing is most likely CODAR.

dxAce
Michigan
USA