American Mobile Satellite Corp. said it lost $29.9 million for the first quarter, compared with a first quarter 1995 loss of $6.3 million. Service revenue growth for the first quarter remained flat compared with the year-ago period, at $1.8 million. However, revenue from equipment sales jumped to $2.6 million from $46,000 a year ago. While the equipment gain illustrates the introduction of voice service and sales to its distribution network, the company attributed its increased expenses to commencing revenue-bearing service, including marketing and staffing requirements. AMSC also reported a $10.3 million charge reflecting the commencement of infrastructure depreciation charges in the fourth quarter of 1995. (AMSC, 703/716- 6522.)