MK484 Portable Receiver
Description:
An AM portable radio receiver made from the ZN414 IC. The ZN414 ic has now been
replaced by the MK484 which is identical in performance and pinout.
ZN414(MK484) Portable Receiver circuit
Notes:
Designed around the popular ZN414 IC this receiver covers the medium wave band
band from approximately 550 to 1600 KHz with the values shown. The coil and
tuning capacitor may be taken from an old MW radio to save time. The ZN414 IC,
has now been replaced by the MK484. The integrated circuit is a 3 pin, tuned
radio frequency circuit, and incorporates several RF stages, automatic gain
control and an AM detector. It is easily overloaded and the operating voltage of
th IC is somewhat critical to achieve good results.
In this circuit a small voltage regulator is built around the BC108B transistor,
four 1N4148 diodes, the 2k7 and 10k preset resistor and the 820R resistor. The
10k pot acts as a selectivity control for the whole receiver, controlling the
operating voltage for the ZN414 (or MK484). If you live in an area that is
permeated with strong radio signals, then the voltage may need to be decreased.
I found optimum performance with a supply of around 1.2 volts.
The audio amplifier is built about an inverting 741 op-amp amplifying circuit.
Extra current boost is provided using the BC109C / BC179 complementary
transistor pair to drive an 8 ohm loudspeaker. The voltage gain of the complete
audio amplifier is around 15. The audio output of the complete receiver is
really quite good and free from distortion. I may provide a sound sample later.
I used a small wooden enclosure and the complete tuning assembly from an old
radio.
ZN414(MK484) Portable Receiver prototype
Circuit : Andy Collinson
Email: anc@mitedu.freeserve.co.uk
Title: MK484 Portable Receiver
electronic circuit
Source: unknown
Published on: 2006-01-15
Reads: 2109
Print version:
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