The custard will present a certain impedance (resistance and reactance, normally represented as a complex number) at a frequency. A radio transceiver normally expects 50ohms (real) at the antenna port for maximum energy transfer (and smallest standing wave voltage ratio). Using a network of capacitors and inductors (the tuner) the custard's impedance can be transformed to 50 ohms. But it's still not an efficient antenna, in the sense that it won't radiate more.