First version of HBR4HF or HBR10HF are used hybrid microphone with loudspeaker. Basic idea using this is to reduce complexity and cost. also considering it as portable radio. How ever there’s a requirement to operate with external audio amplifier or external speaker for better audio receiving. The newest HBR4HF already have internal loudspeaker, and the newest HBR10HF already have audio jack also.
Hambuilder team
Dian Kurniawan 
Dian I received the IRF 590 and IRF530 Transistors. Which is the driver transistor? I need the schematic for the HBR4HF so I can troubleshoot my bad HBR4HF radio. Thanks
Hello,
IRF510 is the driver, IRF530 is the final