Air traffic controller had trouble communicating with aircraft on frequency and experienced difficulty maintaining separation between a UAS and fixed wing aircraft.

Narrative

Aircraft X departed ZZZ en route to ZZZZ Center. Aircraft Y was orbiting in the special use airspace area. Sector X was having equipment issues and was having trouble communicating with the aircraft on frequency. I was trying to get the supervisors attention to see if he needed me to take the sector. I looked back and realized that Aircraft Y was still eastbound heading towards Aircraft X. It was too late to stop Aircraft X from climbing through. I tried to turn Aircraft Y to a 340 heading; given how slow Aircraft Y is he should have been able to stay clear if he had turned at that time. Unknown to me; Aircraft Y was monitoring VHF guard. Sector Y only has the capability to monitor UHF Guard. His voice indicator was still on; leading me to believe that I could communicate with him. I was unable to turn the aircraft to the east away from Aircraft Y because of the restricted airspace. The aircraft were 4.66 miles apart laterally and 700 ft. vertically at the time of loss.I believe when UAVs (Unmanned Aerial Vehicles) are operating in the [named] portion or any other area of the special use airspace area that could be problematic; they should be monitoring a frequency that is available on the controlling sector. If they are not; the voice indicator should be off.