Steve,

There is Aircraft on a Freq of 5.649 mhz USB.Planes flying over the
atlantic They call in & get a SelCal I think they call it????? from
Gander, NewYork, and other land base stations. I think it is called
North Atlantic C or NAT-C

I am not sure the selectivity of your receiver but I doubt this is what
you are hearing.

Sorry not more help.

73, Ken KG4BIG

Georgetown, KY.

Steve wrote:
What am I hearing here? There's a voice uttering something I can't
quite make out, followed by the occasional data burst.

Steve