If your rig can do it center on 435.172. If not use 435.170 as your center frequency. Be sure to use a 67.0 hz pl in either case. I know nothing about AO 73, sorry. 73 John KI4RO <https://mailtrack.io/> Sent with Mailtrack <https://mailtrack.io/install?source=signature&lang=en&referral=johnki4ro@gmail.com&idSignature=22>