[mmaimcal] quarter-wave plates

[Steven T. Myers]

Just a comment on QWPs.  Akeson and Carlstrom used a tunable grid plus
mirror on OVRO for thier mm polarization program.  This would alleviate
some of the bandwidth problems, though I dont see how one could be 
incorporated into our system without tertiaries and sidecabs (I dont
picture it easily fitting into the beam, let alone on in the
optics for every band).  Im not sure what BIMA used, probably something
similar.  We should find out if someone in the group isnt alread familiar
with this.

I also think that the disadvantages will outweigh the advantages of having
circular polarizations, though I would like to see some estimate of losses
incurred (assuming such a device could even be fit into the optics).

  -steve