My CPL school, and my examiner, told me that you must know how to use every serviceable piece of equipment in your aircraft... the only exception being the moving-map mode of a GPS, which you are not allowed to use. (In fact, the school were careful to mark the Loran C equipment in some of their aircraft is "Inop", because without being labelled like this the examiner would be within his rights to ask us to use it.....)
Not sure how this relates to portable equipment, though.....
FFF
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