MK484 Radio with Loudspeaker
A complete AM radio set based on the MK484 IC (formerly ZN414). It uses a PNP transistor and can drive a 150R loudspeaker.
Chad has built a complete radio receiver using 1 IC and a single transistor. The IC requires around 1.2 to 1.6V and this is supplied via the 3V battery in series with 2 diodes 1N4114 diodes, (1N4004 can be substituted) and the 2k volume control.
Coil Details The Loopstick Coil is 2 7/8" in length and 6/16" in diameter. Tickler Coil is 6 turns and is spaced about one inch from primary coil. Primary coil is wound with 28 gauge enameled wire and the feedback coil is plastic insulated similar gauge. I do not know the permeability of the ferrite rod, I would guess it is 50 or so, for this is a ferramic and not powdered iron. The small 18pf ceramic condenser that provides the feedback can be as high as 22pF or even 33pF.
Chads finished receiver can be seen below.
The audio output is amplified by a single 2N404 PNP germanium transistor and can directly drive a 150 ohm loudspeaker. The loudspeaker was purchased from "American Science and Surplus".
Content sourced from Zen SchematicsCircuit: Chad Castagana, Woodland Hills, CA
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