The pilot was conducting his first solo flight in the aircraft type following a short dual check. During his return to Moorabbin he noted what he considered to be a radio failure. He was concerned because of approaching last light, and made a no-radio entry return to the aerodrome. He made two circuits during which he attempted to extend the gear and flaps using their normal, electrically powered, systems. Although unable to obtain a gear down indication and because he was of the opinion that the problem was related solely to the radios, he elected to land the aircraft without considering the use of the emergency gear extension system. The aircraft subsequently touched down with both gear and flap retracted. Investigation revealed that the aircraft battery was discharged. The pilot had not turned on the alternator field switch during the pre-start or pre-taxy checks. He was surprised to learn of the existence of the field switch when it was mentioned during the subsequent interview.