In article ,
msg wrote:

Has anyone made any progress investigating the persistent chirp
or sweep signal heard around 4800 kHz and elsewhere? It is
about S2 to S3 here in No. MN tonight and S9+/-20db in NC/USA
as heard on an internet receiver there.

These sweeps are a form of low resolution radar used to measure wave
heights, ocean currents (sea surface conditions) and are used on several
HF frequency bands although I have not heard of that low a band used.

Maybe you are getting an image.

Just do a Google search on CODAR. You will get a lot of hits.

--
Telamon
Ventura, California