For the last few years there has been an influx of intruders into the 80m amateur band (all amateur bands for that matter). Most of them are using SSB (Single Side Band) transmissions yet they are undecipherable. When you tune into one of these stations it sounds as if you are using the wrong sideband to demodulate the signal but the other sideband fares no better in demodulating the signal. The signal sounds has if it is using a simple method of encryption in which the audio is simply inverted before being applied to the transmitter. Here in Texas the signals always sound like a female voice possibly speaking Spanish. Usually only one side of the conversation can be heard but on occassion you can hear a very weak station reply.
These transmissions are very similar to the ones other listeners have reported as Voice Encrypted Signals and I suspect use the same technology.
This type of transmission has also been heard on 40m and 30m. It appears to be spreading as time goes on.
The recording below is of a station that I recorded on April 28, 2000 at 0445 UTC on 3590 kHz. Notice the digital burst at the begining of the transmission which I suspect is a type of ALE (Automatic Link Astablishment) system. If you know anything about these illegal intruders any information would be appreciated.