There seems to be multiple goals at play here. I'm not sure that there is one mode that will be best suited for all of them.
Goal 1: Provide a mode that will encourage non-satellite hams to become interested in AMSAT based on what they see at Field Day.
Some think that if you reduce the qrm by using L/U or L/S, more will be likely to get into satellites because there is no crowding and no sign of chaos during Field Day. Why present a false impression? Things do get crowded; you find a way to make your contact in spite of the conditions. Think about it and find a way that works for you. Refine it based on experience. This is what ham radio is all about. There is no best way that works for everyone. You just work with what you have. If you want a clear private channel, satellites are not the solution.
Limiting AO-51 to L/U or L/S means that not many clubs will be using AO-51 to demonstrate satellite operations to the non-satellite people. Not many have equipment for these modes; most will try a V/U bird and not bother with AO-51 if it is in L/U or L/S. The driving force for clubs to work satellites is the 100 bonus points. Since most people have FM radios, they are going to try for the V/U birds. This is the entry level for any new satellite operator. You don't start with L/U or L/S because it is costly compared to V/U and we don't have a bird that is in those modes very often.
Goal 2: Make working AO-51 challenging It is certainly a challenge to get things working on L/S or L/U. Only a few have equipment that they use when AO-51 is in these modes. It's mostly the same people every time and a very small percentage of the total satellite population. You are not challenging very many by using these modes; only a few will try.
Goal 3: Get more people to participate in the AMSAT contest that runs concurrently with Field Day. A voice contact on AO-51 mode L/U or L/S is worth one point. If you are trying win a contest, why expend all that effort to get on these modes when the reward is only one point? If you want people to spend the effort to get on these modes, make it worth their while. Give 25 points for an L/U or L/S contact. I might even take down my 13T W7LRD Helix and haul it over to field day for 25 points! Otherwise it's going to stay right where it is on the tower.
Now a few notes about my experience from last year's field day contest:
The Northern Ohio DX Association placed first in the AMSAT competition in 2009, Doug KD8CAO made the voice contacts and I made the CW contacts. We were the only entry that made both a L/U and a V/U contact on AO-51. Interestingly, we were not able to complete a contact on AO-27. We did make a contact on SO-50. We were also very fortunate to make a contact with the ISS and that, by far, created the most excitement at our Field Day even if it did not count as a qso for the ARRL or the AMSAT competition.
You make your points on the SSB/CW birds. We had 24 SSB contacts and 15 CW contacts on AO-7, VO-52 and FO-29. If we have HO-68 in this mode for Field Day, you can expect scores to be higher than in 2009. The linear birds were pretty crowded and there was qrm. But it was no different than operating on the HF bands as someone else mentioned. Those that were watching and listening were certainly not discouraged.
One of the top contenders in last year's AMSAT Field Day competition would not work us because they had made a contact with us on another bird. So you waste time trying to contact someone and finally get through only to be told you're a dupe. Yes, you are a dupe under the ARRL rules so you can't count the contact there, but you can and should count the qso for the AMSAT competition. There is no conflict here; you just don't submit those ARRL "dupes" as valid qso's. You can be in both contests and play by both rules.
Suggestion for 2010: If at all possible, run the same modes as last year, L/U and V/U. Adjust the power levels to 400mw on each transmitter if the power budget will allow it. If only one transmitter can be supported, use V/U. Many more will try to make a contact and that is what we want to encourage. If you have it in L/U or L/S, not many will try. We should be striving for a mode that will be attempted by as many clubs as possible. AO-27 is a great bird but it is always at a high elevation over the US when it is "on." You can work AO-51 when it is much lower on the horizon, thereby reducing the number of stations trying to use it. You are more likely to make a V/U contact on AO-51 than you are on AO-27 because of that. Our experience last year bears this out.
I think there is more potential to make qso's on AO-51 in the V/U mode this year because the first pass comes over the east coast very early, around 5am Sunday morning. If the bird is in L/S for Saturday's passes, the mode should be switched to V/U early in that pass out over the Atlantic if that plan is chosen. Last year the first pass was at 6:45am EDST.
NODXA will be on the birds at Field Day this year but it is likely that we will not be out to win. I'm planning a very casual operation. Our callsign is W8DXA. Good luck in the contest!
73, John K8YSE
John Papay john@papays.com