Mobile wireless communications device using wired headset as an antenna and related methods

A mobile wireless communications device may include a housing, and circuitry carried by the housing. The circuitry may include a wireless transceiver, a wireless broadcast receiver, audio circuitry coupled to the wireless transceiver and the wireless broadcast receiver, a wired headset jack, and a reference voltage device line, and at least one wired headset device line coupled between the audio circuitry and the wired headset jack. The reference voltage device line may be also coupled to the wireless broadcast receiver so that a corresponding reference voltage headset line of a wired headset serves as an antenna for the wireless broadcast receiver. The reference voltage line may be switchable to one or more connectors at the headset jack.