B777 Undifferentiated or Other Model
Flight Crew Air Transport Pilot (ATP)
Communication Breakdown; Confusion; Time Pressure
ATC Issue All Types; Conflict Airborne Conflict; Deviation / Discrepancy - Procedural Published Material / Policy
Air Traffic Control Issued New Clearance; Flight Crew Took Evasive Action
ATC Equipment / Nav Facility / Buildings; Procedure
North of ARVUM at FL360 in continuous moderate+ chop we requested FL340. Amazonica initially denied our request but subsequently cleared us to FL340. Upon reading back our clearance to FL340; Amazonica confirmed our clearance to FL340. Almost immediately Amazonica re-cleared us to FL360. Pop up traffic opposite direction appeared at the limits of TCAS 40nm; level at FL350. We were approaching 35;200 feet as we climbed back up to FL360 and assumed a right 1 mile offset. We were never closer than 30 miles to the opposite direction traffic before leveling at FL360. No TA or RA was received. While Amazonica has radar coverage throughout their airspace; their radios for the most part are atrocious. Constant vigilance is necessary and my alert copilot safely and smoothly maneuvered us to a safe altitude and course. Communication is extremely important in our profession and while read backs; and confirmation are necessary operational procedures; good radios are of paramount importance! A better means of communication must be found to mitigate communication errors; especially in remote and oceanic areas.
A B777 aircraft received a clearance to descend to FL340; and almost immediately were re-cleared to FL360. They noted pop-up traffic on TCAS at FL350 at 40 miles away.  The reporter notes the poor condition of Amazonica's radios.