Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument
Flight Crew Last 90 Days 198.45; Flight Crew Total 13042.08; Flight Crew Type 2746.85
Troubleshooting; Situational Awareness; Communication Breakdown
ATC Issue All Types; Deviation - Altitude Excursion From Assigned Altitude; Deviation / Discrepancy - Procedural Clearance; Inflight Event / Encounter Weather / Turbulence
Aircraft Equipment Problem Dissipated
ATC Equipment / Nav Facility / Buildings; Airspace Structure
We encountered moderate; approaching severe turbulence at 39;000 feet. There was was a SIGMET for the area to our south for turbulence 32;000 feet to 40;000 feet; I requested 30;000 feet and received clearance to 30;000 feet. We began a descent and the turbulence stopped completely at 38;500 feet. I slowed the descent and requested 36;000 feet. We had no response and continued a slow descent. PANZ then queried if we were still descending to 30;000 feet. I asked again for 36;000 feet and we were cleared to 36;000 feet. At 34;500 feet we began a climb to 36;000 feet. About that time ATC contacted us on VHF and clarified why we were descending so slowly. I responded that I made 2 requests for 36;000 feet and also tried on VHF. There is a VHF dead zone of about 180 miles between 2 remote transmitters and we were unable to make contact at the initial descent.
Air Carrier Captain reported an VHF radio dead zone.