How to make a modern radio receiver transmit?

When I was growing up transistor and tube radio receivers were common. Although I didn t do it, from what I understood, the common way to transmit through a receiver on the proper channels was to connect a powered speaker/microphone to the speaker out jack. Then using a switch which switched the jack from speaker to mic and back polarity was reversed which allowed transmitting to ground. In other words the mic was grounded a the mic power supply powered the tranmitter and the path to the antenna was ground. Something like that. US of A government actually requires the manufacturer to tell you if the receiver will work as transmitter and how to do it and that was the common way. Modern receivers use chips like CPU and DSP so it may be impossible since fixed grounds a chip amplifiers are common. It is best to buy radios that use coils capacitors and transformer if you are thinking you d like to use it other than a receiver. Otherwise you have to make a transmitter board than goes in the case and disconnects the receiver completely and it probably will transmit incorrectly.