Rangkaian AM Receiver merupakan salah satu rangkaian yang di desain khusus sebagai reveiver atau penerima radio dengan sumber tegangan DC hingga AC. Rangkaian AM Receiver This is 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.
All general purpose transistors should work in this circuit (Rangkaian AM Receiver), I used three BC549 transistors in my prototype. The tuned circuit is designed for medium wave, but the circuit will work up to much higher frequencies if a different tuning coil and capacitor are used. I used a ferrite rod and tuning capacitor from an old radio which tuned from approximately 550 – 1600kHz. Q1 and Q2 form a compound transistor pair featuring high gain and very high input impedance.
This is necessary so as not to unduly load the tank circuit. Q1 operates in emitter follower, Q2 common emitter, self stabilizing bias is via the 120k resistor and the tuning coil. As Q2 operates in common emitter its base voltage will be a Vbe drop higher than ground or about 0.71V in my test sample.
The voltage at Q1 base will be this Vbe drop plus the voltage drop across the 1k resistor and Q1′s own Vbe drop, this amounted to 1.34V from base to ground in my test circuit. For audio amplifiers, Q2 collector would be biased near half supply voltage, however the input signal levels at RF are tiny, typically 50uV appearing across the coil being amplified by Q2 and being about 5mV RF across the 2k2 load resistor.
Berikut ini Gambar skema Rangkaian AM Receiver :
The 120k resistor provides regenerative feedback,between Q2 output and the tank circuit input and its value affects the overall performance of the whole circuit. If you are in an area of weak reception then an external antenna may be required. Wind about 4 or 5 turns (indicated as 4 or 5 T on the schematic) of 26 SWG wire onto the ferrite rod, close to the main winding and connect one end to a cold water tap or ground connection. Use several feet of flexible wire as an antenna.
Demikian penjelasan singkat mengenai Rangkaian AM Receiver. Sekarang sudah jarang orang memakai Radio AM, tapi sebagai bahan referensi untuk ilmu pengetahuan tak ada salahnya Anda mencoba membuat AM receiver.