In a search for info on Sitton Peak I found a 2009 USFS initial planning blurb or "Proposed Action" for a repeater
Schedule Of Proposed Action - 01/01/2009 to 03/31/2009 - Cleveland National Forest
Description: The Forest proposes to install a Forest Service radio repeater at Sitton Peak T7S, R5W, Sec 6.
Location: UNIT - Trabuco Ranger District. STATE - California. COUNTY - Riverside. LEGAL - T7S, R5W, Sec 6. Sitton Peak.
The legal description translates to:
Section S6 T7S R5W
Meridian San Bernardino
State California
County Riverside
COMTRS 33S07S05W06
Centroid33.5881397, -117.4417639
Corners
NW33.5979233, -117.4503469
NE33.5982286, -117.4332031
SE33.5783012, -117.4330961
SW33.5781941, -117.4504689
The centroid shows something rectangular along the hiking trail but I don't think it is a repeater as I would expect some solar panels.
33°35'17.6"N 117°26'29.9"W
In the image there is something white and sort of pole shaped down and left about 40 feet away