Air Traffic Control Fully Certified
Communication Breakdown; Human-Machine Interface
ATC Issue All Types
Air Traffic Control Issued New Clearance
ATC Equipment / Nav Facility / Buildings; Airport
I was working Local Assist. Aircraft X was instructed to line up and wait on Runway 1R. When in position; the Local Controller attempted to reach Aircraft X on the frequency several times; but was unable. This has happened many times before with lower profile jets (smaller Citations; Lear Jets; Phenoms; etc). There is apparently a dead spot where the tower antennas do not reach low profile jets while they are in position on Runway 1R. The only way to reach them is to relay a message to them through another aircraft. I told the Local Controller about this and told them that they should tell an air carrier jet who was holding short of Runway 1R to instruct Aircraft X to move up a few feet to get out of the dead zone. We re-established communication with the jet and cleared it for takeoff. Tech Ops needs to find a solution so that the entirety of all runways are receiving radar coverage for all aircraft types. This problem should not persist as it could potentially lead to some very unsafe situations if; for instance; cancel takeoff clearance instructions are not heard.
SFO Tower Controller reported a radio 'dead spot' identified at the approach end of Runway 1R that continually affects lower profile jets when in position on the runway.