Steve's suggestions are all right on. You ought to be able to get this worked out on the ground without burning avgas. The only other thing I'd add, since this is a new GDU 4xx installation, is to verify you have updated your display software to the latest version, which will include the correct audio database.
RV-7 (last 90%)
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Last edited by mburch : 07-02-2022 at 10:05 PM.