Can you reduce the number of bits that you are using?
With radar signals, the receiver noise most of the time excites only about 8 bits out of 16. Ground clutter or meteor echoes excite nearly all of the bits occasionally, so I can't just truncate to 8 bits. In this case, bzip2 actually does a pretty good job of getting rid of the 8/16 most significant bits that are zero most of the time. Thus, I get a compression ratio close to 50% when using sc16. pbzip2 is a good tool for doing parallel compression on files.
juha