https://www.idahofireinfo.blm.gov/southwest/documents/maps/BOF19-RadioCoverageNorth.pdf
yikes - looks like 30% dead spots
maybe those are areas that are too steep for hand crews
Nothing is too steep for hand crews, specifically Interagency Hotshot Crews (IHC). They have climbing gear and have built line and mopped up where they are roped in. Every effort is made to avoid this type of work. Generally the steep areas are void of vegetation. Often times fires are allowed to burn out in steep areas as the uphill side of steep slopes usually turn to rock or very sparse fuels. IHC crews were deployed on the east side of Mt. San Jacinto in the area of the Palm Springs Tram. In this case the vegetation got thicker as the elevation increased and a fire started on this slope, which gradually turned to conifer trees near the top, where the top of the tram and state park facilities are located. The forest gets more dense almost to the top of this prominent southern California mountain. The fire had to be contained on the steep slopes before arriving to the top of the tram area, which is located on a large bench. Otherwise it would have burned into very dense forest.
IHC's have climbing gear primarily for rescuing injured firefighters taken out on litters, backboards, etc. Sometimes there are cliff bands, rock faces, etc. which the injured have walked around as they gained elevation, but rescues often need to go straight down the mountain.
The dead spots are just normal shadows of multiple repeater sites. To gain a higher percentage of coverage, sometimes there needs to be a repeater on the ridge of every large canyon.
