171.985 is not a valid channel. It is 2.5 kHz away from 171.9875 which I answered in the other thread.
All federal frequency assignments in the 138-144, 148-150.8, 162-173.2, 173.4-174, 380-400, and 406.1-420 MHz bands are on 12.5 kHz steps. (171.975, 171.9875, 172.0, etc...). There are a few exceptions for some extremely narrowband data modes but not for normal base/mobile/repeater voice communications.