Not to disagree with "Dish", but 311s are 8PSK, 301s are QPSK and going away. 501, 508, 510 all QPSK. Any receiver with 4 digit model numbers, aside from Hopper, are QPSK (technically the Hopper is a model "2000"). Model 521 & 721 are also QPSK, but I think they were all replaced long ago. Model 381 (an 811 MPEG 2 HD - converted to just SD) is QPSK. Model 921, not sure if it is QPSK or 8PSK, but I don't think there are any of those around anymore either, all original MPEG2 HD receivers have been replaced with MPEG 4 versions, which also included 942.