RADIO cooking is the latest stunt developed by broadcast engineers. If a hot lunch is wanted by the operators in a transmitting station, all they have to do is place their food between the electrodes of the transmitter. In a few moments it will be done to a turn. Bread may be toasted in six seconds, but steak and potatoes take several minutes. Oddly enough, food overdone by cooking on the radio transmitter does not have a burned taste. Toast can be charred black without tasting in any way different from the kind a cook would be proud to serve. Engineers are not quite sure just why this is so, but believe it is because the cooking is done by the electric discharge and the electrodes get only slightly warm.