Littleton-based EchoStar Communications has filed a revised proposal with federal regulators to buy Hughes Electronics. Direc-T-V. EchoStar submitted the plan with the Federal Communications Commission yesterday but declined to make the filing public. Spokesman Marc Lumpkin says the company will let the F-C-C when and how to release the details. The F-C-C has not yet posted the material on its Web site. The F-C-C and Justice Department said last month that the 18-point-eight (b) billion dollar union would create a monopoly in rural areas and reduce choice in almost all other areas. EchoStar must pay a 600 (m) million dollar breakup fee to Hughes if the merger does not go through by January 21st. If Direc-T-V pulls out before then, it must pay EchoStar. Both companies must show that they took all possible steps to get the merger approved to avoid paying the fee.