The opportunity has come up that I might be going to either Poland (Krakow) or Romania (??) in a month. (business trip)



Is anyone familiar with the technicalities of operating from either of those countries?



In a related question, any thoughts on an easily packable antenna that might let an 857d reach back to the states?

Any light weight power supplies I can pack, or do I need to improv somthing when I get there?

I've worked that part of Europe with my ultimax 100 end fed wire antenna. That would pack small.
I'll let others with more exp chime in on the rest.

CEPT makes it automagical!

http://www.arrl.org/cept

You will most likely have to apply for a reciprocal license to operate from either of these countries. That's if we have a reciprocal license agreement with them. Best check with the ARRL and ask them what the procedure is to operate there.

Cover in jeopardy he plots a return to his eastern european roots...Your english was always just a little TOO good comrade.

I operated from Chezh Republic earlier this year.  Bring a copy of CEPT document (it contains reciprocal information in three languages ) ,  your FCC license and obviously your passport.  Also search frequency charts applicable to those countries. Print it out and bring with you.
I believe CEPT agreement gives full privileges too US extra class licensees.  There may be restrictions if you are a general.  Technician license holders are not eligible. Read about it.

I brought my FT817D with me but wished I brought my ft857 instead. The only antenna I could practically use was a BiddiStick.  In Europe they dont build buildings out of sticks and plywood like in the US. Everything is brick and concrete with rebar. Operating from a hotel room is not going to be easy. I was lucky to have a balcony where I mounted the antenna. Buddipole was marginally better than a dummy load and it was a pure pain to tune properly. I had to use my MFJ Travel tuner to bring SWR to acceptable levels. An End-fed antenna would have been a much better choice but I had no where to hang it.
MFJ Mighty Lite 25 A power supply would  be your best choice. It accepts both 120 and 230 VAC but you will need a plug adapter. I suggest to buy at least 3 adapters because you'll need them to run your radio and charge your phone, computer etc. European to American adapters can be found on ebay.  I bought a pack of 6 for a few bucks.
I strongly suggest to find a local club in the area you are going to visit. They will most likely let you operate their club or personal station. I had a very warm welcome from Chezh hams. They let me operate from their club's contest station. Language was a bit of an issue. I dont speak Chezh. We used a mixture of English and Russian to communicate. A few guys spoke German too.  No problem.
Having a 4 square, 8 element each array on 20,15 and 10 meters was nice. And they had an Acom legal limit amp to supplement the antennas. I had a blast handling a pileup of American stations calling me. I turned the antenna East and there was a pileup of russians calling.

No need to apply for a separate license if the country has a reciprocal agreement with USA.  He will need to id as for example OP/W1AW.

I've used the alexloop several times while traveling. I also have a buddipole pkg but haven't used it as much as I am still working out which configurations work best. The only downfall to the alexloop is 20 watts max. Doesn't effect my sgc 2020 but would limit your 857.

For an antenna, maybe a few par-endfedz and a collapsible crappie pole?  Could use vertically in the open or hang the par off the end upside-down.

I have been impressed with the par-endfedz on my SOTA and USIOTA activations.  They will probably be the antennas of choice in the BVI as well.

QSO!

Part of this will depend on how much baggage allowance I can get from the company. I'm not sure how much weight/volume I'll have left over after packing warm clothes, laptops, etc. Oh, yeah... and allotted extra space for bringing back goodies.

FT-857 is perfect. You'll need some extra TX power if you use a small and inefficient antenna. But like I said before, find a local club in the area you will be staying. You'll have a blast operating with good antennas and probably a kilowatt amplifier.
Also bring good walking shoes. You will do a lot more walking than an average person does in the US. European cities are more compact and densely populated. Everything is within walking distance (several miles).