SO2R

I keep returning to my experience at Contest University because (a) it was exceptionally well done, taught by some of the top contesters and DXers in the hobby, and (b) I believe there is a significant overlap between DXpedtioning and contesting. Both activities require that QSOs be made during a fixed period. Both activities encourage working stations quickly.
Randy Thompson (K5ZD) covered the Single Operator 2 Radio (SO2R) subject mid-morning at CTU. Like most of the instructors, Randy began with a quick review of his accomplishments (which are considerable). Just a quick peek at his QRZ page and you'll see he makes an average of 20000 QSOs per year. I have not made even half that many in the last four years!
What is SO2R? It is a single operator seated in front of two radios. Ideally, there is additional hardware that helps route audio from both radios to your headset with options like one-radio-per-ear, or mixed to both ears. The extra hardware might also help route various antenna feed lines to the two radios and lock out transmission of one radio if the other radio is already transmitting. Fully automating such a system becomes quite a complex problem. Examination of products such as the MicroHAM MK2R provide some insight as to how hard this problem is to manage.

What problem are we trying to solve? Reviewing the DXpedition statistics for the VP2M DXpedition, you can see we made no contacts on 10m or 12m. It isn't that we didn't try. We did. But, if there was an opening, we missed it. One of the problems that a second radio (or at least a second receiver) can solve is identifying irregular band openings. The Northern California DX Foundation maintains a world-wide beacon network that makes it very easy to see if there is a band opening interesting to you. If you have one receiver, you need to make a choice. Should you stop making QSOs on your current band to check for openings on the other band? Or, should you ignore the other band, perhaps missing an interesting opening in the process? A radio with a single receiver gives you only these choices.
A radio with a second receiver like the FT-1000 or new Elecraft K3 gives you a second option: listening on the second band while you continue to work on your primary band. This option is one of the reasons why I am so interested in the K3. In a contest, that means you can look for multipliers on the second receiver while continuing to run on the main one. In a DXpedition, you can look for band openings either by hearing beacons, or even QSOs, on another band.
A second full radio, with full transmit capabilities, allows you to call CQ on two bands at once. This is illegal in a contest, but nothing precludes it on a regular DXpedition! Who knows, if we had been calling CQ on 10m all day while on Montserrat, we may have been the signal alerting others that the band was open! I believe lots of openings come-and-go because nobody bothers to call CQ. With automatic CW and voice keyers, good band-pass filters, and an alert operator listening on two bands, there is an opportunity to work many more QSOs than the single radio operator. Randy Thompson confirmed many of these claims in his presentation.

Bringing a separate radio when you are carrying your own gear (and trying to live within the 100 pound weight budget) may not be possible. If you are shoping around for a DX location already stocked with great ham gear, you might start with DX Holiday with their Rent-a-QTH program. There may already be an SO2R system there, or enough stuff you could cobble together one during your visit. Note that the very best SO2R stations are not cobbled together! They are carefully crafted with filters and stubs to manage inter-radio interferrence, and have an SO2R hardware system that routes audio, microphone lines, and antennas. Trying to build something like this on your DXpedition violates one of my main rules: keep it simple! All that said, I believe that if you can do simple things that can achieve some of these goals, it would likely be worth the effort.

My recommendation (and Randy's) is to become effective and comfortable with one radio before you attempt adding a second one to the mix. But, when you are ready to "graduate" to that second signal source, it would be best to begin with a second recevier. Listen for band openings. Listen to other signals on the band you are working. Don't lose your calling frequency, but be aware of other things going on. Since this capability adds nearly no weight to the DXpedition (a second receiver inside your radio probably weighs ounces), it is an excellent way to try this approach without blowing your weight budget.
Finally, and I make this point about most things, you should work out all the details of a particular approach or practice before you go on your trip. Practice. Practice. Practice. If you believe you'd like to try using a radio with a second receiver on your trip, try using it at home first. Don't spend your precious island time working out skills you should have mastered at home.

Subject change: June is Field Day month. Field Day can be a great opportunity to practice packing, deploying, and using equipment away from home. I'll be working with my local club putting up some antennas and sharing other tidbits. Plan ahead. See you on the air!