rf circuit
A simple MK 484 IC tuned rf (trf) radio
In 1970 Ferranti started the development of a single-chip AM tuner, and by 1973 it became widely available for use. The 414 is no longer in production, but a follow on IC, the MK484 recently became available, and incorporates essentially the same features. It is a 3 terminal device which packs ten transistors providing 3 stages of rf amplification with an input impedance of about 4 Megohms, and giving 72 dB of gain with about 30 millivolts of audio output (rms). Thanks to the editors of Practical Wireless a ham magazine in the UK, and Dr. Philip Miller Tate of Kingston University, who has probably built a dozen or so of these in one guise or another, and sent me one fully assembled, here is one adaptation of this versatile little chip which gives you a nice little portable radio which is stable and virtually idiot proof to build, needs only a 1.5 v battery, and requires a tiny thimble full of parts to give you near-superhet performance. Here is the schematic of the circuit that PW came up with:
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