Sorry, talking at cross purposes. I accept that for instrument approaches (ILS or VOR) you would need FM immune NAV radios (in the real world I fly NDB or SRA approaches, in fact). What about en-route tracking of a VOR outside CAS but in IMC, though? That's an IFR flight so AN84 implies you can't do it legally, yet there's nothing in the ANO to prevent it - does AN84 override the ANO? Or does it come under the catch-all 'equipment required to complete the flight' bit?
Tim