Pactor IV

SCS introduced their new Pactor-IV "Dragon" modem in 2011, but it wasn't heard much on the bands until late 2012. The major change is seen here, with the two rising audio tones slowly sweeping out about 950 hertz each. Nothing else currently on the air sounds even slightly like this; not even the "Whales" or "Backward Music."

This appears to be a 2-way contact, with one signal only partially quieting the noise, while another one goes to full AGC.

Plot made with Spectrum Lab.