This is not the "Pilot Butte" that you think you will activate in an easy afternoon within the City Limits of Bend. Its prominance is only 468 feet for a 4138 foot elevation. The Pilot Butte you want to activate is the 5780 foot high 4 point summit with 1400 feet of prominance that's about 20 miles east of Prineville.
The roads off the public highway cross the property of several different landowners and the summit proper is on private land. You may find that access is restricted. Here are directions that may get you near Pilot Butte:
On the east side of downtown Prineville, turn south on Combs Road and go 17.2 miles on Oregon 380, the Paulina Highway. Onto an unnamed road (just past a substation) turn left (north) and go about 2.3 miles to turn left and continue towards the NE. After 2.8 miles turn left again, heading west. About 1.8 miles later there should be a road leading off to the right that will head up to the summit. There may be a gate. The summit is about a mile up the road - there is an RF site at the top of unknow QRM potential.