Caught the last couple of minutes only.
Signal was unstable at one point but then returned to its center frequency after a second or two.
Sounds like AM with MCW while listening on USB. Fading was prevalent but no interference
from ham ops as this is in the ham band.
Signal peaked to about 20 db over the noise with one fade almost into the noise.
mp3 file linked here.
http://dl.dropbox.com/u/54521034/Numbers%204-6-12%201316Z%2018.106612%20MHz%20USB.mp3weaksigs