Budget Fm Receiver

18 BUDGET FM RECEIVER J.Bareford Most receivers for 30 MHz and up contain a fair number of semiconductors. Although super-regenerative receivers have been built with few transistors, their performance is generally rather poor. The present four-transistor receiver is of the super-heterodyne type, and demonstrates the feasibility of building a sensitive FM receiver from a minimum number of components. Although the super-heterodyne receiver requires relatively many sub-circuits, it is probably the best choice when a receiver for the VHF and UHF ranges is to be built. The first building block of the "superhet" is the input stage that filters and raises the aerial signal to a level suit- able for the second block, the mixer. The filters are required to ensure sufficient image rejection. The third block is the local oscillator. This circuit is tuneable and drives the other input of the mixer. The output of the mixer is connected to the input of the intermediate frequency (IF) amplifier ...