The past several days, there have been significant non-amateur interference sources showing up in the middle of the 40 meter band. Intially, it sounded like a local power supply noise source -- but after some investigation and hearing other hams up and down the east coast were experiencing the same phenomena,I'm thinking this is some type of instrusion using an unknown digital modulation scheme.
Yesterday, the noises were nearly identical clusters of (4) RF "humps" centered around 7.110, 7.130, 7.140, and 7.170 MHz. Listening in LSB they made a growling noise -- and stayed centered on those frequencies with little to no discernable drift. They were apparent most of the day yesterday and the day prior. A ham in Florida had gotten a signal peak with his yagi towards Cuba.
Today at 2010Z (and continuing) -- we have as many as (10) similar data streams from 7.105 to about 7.165 MHz, each occupying about 5 kHz -- they sound like bullfrogs. Any weak signals here would be toast. Those of us old enough to have experienced the Russian Woodpecker don't want to go back to those days...
Update: There's an ongoing thread on http://qrz.com QRZ Forum discussing this topic, with a popular theory being intentional jamming by the Cuban government as a response to uprisings in the country and fallout from the Haitian president being assasinated.
Reddit thread on 40m Interference
In researching this, came across an application that's been available for TDOA (Time Difference of Arrival) direction finding in KiwiSDR. This has a great deal of promise for tracking down interference sources. There's also been circulated information that this same SDR has / (had?) a baked-in backdoor for access by "the developers" -- which is concerning. TDOA in KiwiSDR
