I suspect that Chris will give you a better answer, but the Refcom preselector is like an antenna tuner. Basically you fool the reciever into seeing a resonate antenna. On a transmitter one can do this manually with an SWR meter, use an auto tuner or use an antenna analyzer, which actually sends out a very low RF signal and then analysis its swr. This does this manually by swithing capaciters to "tune" the antenna to each band.
The DSP is a digital signal processor. Basicaslly this is a filter, which cuts out unwanted frequencies--on ham and ssb signals there are both man made interference and natural interference--like from sun spots. With a DSP you can make very sharp cut offs of the actual signal. I have tried extrenal DSP's in the past, and they are helpful.
The Yaseau 5000 is a high quality reciever--and I suspect that Chris will use it for weather--I would prefer to have a full transciever, so one could talk to the rest of the world--and since ham radio licenses are easier than ever to get, would suggest that anyone going to remote areas have a ham set.
We have an Icom 7000. This transciever is very small, and can even be remote mounte, with just the face showing. It has built in DSP,s comperable to what the DSP Chris has. Its DSP are on the RF--radio frequency as the signal comes into the set, rather than just the audio output. We use an automatic tuner for frequencies other than the specific ham bands--where we use a tuned antenna (Ham Stick).
Question for Chris--are you gong to have a Ham radio transciever aboard also?
Regards,