Felix wrote:

Hi,

I'm trying to identify a data transmission I keep hearing on 3132khz.
According to the FCC frequency allocation chart 3132 khz belongs to
aviation. Does aviation use data for transmission? I'm only aware of
ACARS, and thats in the 130Mhz range.

Has anyone heard anything in the 3mhz range? I've recorded a minute
worth of the sound, if anyone is interesting in hearing it (perhaps
someone can identify the mode) email me back and I will send them the
file. It's about 800kb.
snip

I hear an ~5hz warbling signal on 3132 at 1800Z here in No. MN;
propagation on that band is very poor at this time of day so lots
of QRN and signal barely audible.

Please send me the audio clip; unmunge the From address.

Regards,

Michael