OnNE CHIP AM RADIO RECEIVER CIRCUIT SCHEMATIC DIAGRAM

ONE CHIP AM RADIO RECEIVER CIRCUIT SCHEMATIC DIAGRAM

The MK484 we use is a Japanese copy of the original ZN414. It contains an RF amplifier, active detector and automatic gain control (AGC to improve sensitivity) all in a 3-pin package. The input impedence is typically 4M ohm. It operates over a range of 150kHz to 3MHz. DC supply of 1.1V to 1.8V & 0.3mA current drain makes it ideal for battery operation. The output is typically 40 – 60 mV of audio signal. Optimal AGC is provided by R3 and C2 (see Figure 2). R3 (the AGC resistor) should be in the range 100R to 1.5K. A bandwidth of about 4kHz is achieved.

AM RADIO RECEIVER CIRCUIT SCHEMATIC DIAGRAM

AM RADIO RECEIVER CIRCUIT SCHEMATIC DIAGRAM

The circuit use a compact three transistor, regenerative receiver with fixed feedback. It is similar in principle to the ZN414 radio IC which is now replaced by the MK484. The design is simple and sensitivity and selectivity of the receiver are good.

9V FM RADIO TRANSMITTER CIRCUIT SCHEMATIC DIAGRAM

9V FM RADIO TRANSMITTER CIRCUIT SCHEMATIC DIAGRAM
The frequency range of this FM transmitter should be about 89MHz – 109MHz. Output power is about 9mW at 9V.

ACTIVE RADIO ANTENNA CIRCUIT SCHEMATIC DIAGRAM

ACTIVE RADIO ANTENNA CIRCUIT SCHEMATIC DIAGRAM
On the shortwave band this active antenna is comparable to a 20 to 30 foot wire antenna. This circuit is designed to be used on receivers that use untuned wire antennas, such as inexpensive units and car radios.

CIRCUIT 1.5 WATT FM TRANSMITTER SCHEMATIC DIAGRAM

CIRCUIT 1.5 WATT FM TRANSMITTER SCHEMATIC DIAGRAM

P1 act as condenser microphone volume level. For FM, coil will be small. Use thin gauge enamel magnet wire. the diameter of coil will be a couple mm: use ink tube from pen to form, and try 8-12 turns. Small inductance coils make for much guess work.

Components List
R1=220K
R2=4.7K
R3,R4=10K
R5=100ohm C1,C2=4.7uF Electrolytic
C3,C4=1nF
C5=2-15pF
C6=3.3pF Q1=BC547C
Q2=2N2219A
P1=25K
MIC=Electret Condenser Type