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  • This two transistor AM radio circuit is also called “mini-radio”. It uses only 2 transistors and few passive components which makes is very easy to be constructed. Although the circuit is very simple, it functions very well without external antenna or ground connection. The transistor T1 works as a feedback regulated HF-amplifier and function as demodulator at the same time. The sensitivity of the receiver is dependent on the amount of feedback and can be adjusted by P1.

    Transistor radio circuit schematic

    two transistor AM radio receiver circuit schematic

    The demodulated signal comes out from the collector of T1. The signal is then filtered by C3 so that only the audio signal will be amplified by T2. The amplified signal is then delivered to a high impedance “earphone”. The coil is 65 turns AM antenna wire around a 10 cm long x 10 mm diameter ferrite rod. The tap is at the fifth turn of the coil counting from its ground end. The coil must be installed as close as possible to the PCB.

    The sensitivity of the radio receiver can be greatly improved by attaching an external antenna into it. The external antenna must be coupled to the hot end of the coil through a 4.7 picofarad capacitor. The radio receiver cand be powered by a 9 volt battery. It consumes only 1 mA.

    2 transistor radio PCB layout

    radio receiver pcb layout

    Transistor radio parts placement layout

    radio receiver parts placement

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    19 Responses to "Two Transistor AM Radio Receiver"

    1. It is very good presentation!

    2. Christian says: on March 10, 2010 at 9:41 am

      Will this work?

    3. Th3_uN1Qu3 says: on March 11, 2010 at 1:05 am

      Um, build it and find out. By the looks of it it’s a scan from an old electronics magazine, so it should work. In case you haven’t figured, this is an AM not FM radio, so depending where you live you’ll either get lots of rstations (in the US), or three stations (such as here in Romania).

    4. how can i make this type pcb

    5. Dont expect good performance, this radio will pick up locals and locals only. This is a regenerative reflex receiver and you may have issues with unwanted feedback, even with the regen control all the way down like I did. Otherwise this is a great circuit and it uses no transformers or chokes which makes it easy to build in tight areas.

    6. Hi, I was wondering if you could provide terminal (emitter, base, and collector) voltages you measured (or calculated) for the 2 transistors. It would be very helpful to me. Thank you!

    7. 2sc3112 2sc2675 Equal to transistor ?????

    8. Thought, any general purpose NPN transistor, like BC547, 2N4401 etc… For using the PNP transistors its only needed to reverse the polarity of the battery and electrolityc capacitors. Good luck!

      PS Its an old, good and simple schematic will work for sure

    9. what does the p1 means sir?

    10. in need to know what the point A,B and C are …

    11. how that circuit can get voltage to 9volts to 6.8k to 39 k that’s impossible to get supply that circuit

    12. Stevezilla says: on January 19, 2014 at 6:18 am

      re: “in need to know what the point A,B and C are …”

      Answer: Antenna (see schematic)

    13. Hillarysantus says: on February 6, 2014 at 3:48 pm

      pls i will like to recommend ur cct to ma course mate and lecture on a note of assurance that it will work.
      pls reply me via email.

    14. how rf signal demodulated and detected

    15. Sirs

      The configuration seems to me keeps the T1 just on the point of cutoff. If the potential at C4, R4 hot end should rise that would increase the biasing of T1. T1 will then “suck” away the biasing of T2. Current through T2 would decrease and the potential at C4, R4 hot end would decrease back.

      The transfer curve of T1 at the brink of cutoff is heavily nonlinear ie curved. Thus negative signal halfwaves will almost shut T1 off and positive halfwaves will be amolified. Thus detection will happen at the collector of T1.

      Reflexive coupling means that a HF stage performs both as a HF amplifier and detected LF amplifier. It seems to me that there is no LF feedback to T1 in this circuit.

      Best regards

    16. Re: the A,B,C terminals- they are marked this way to show the 3 wire connections to the antennea/transformer and that that this antenna bar coil/transformer is not mounted on the same circuit board as the rest of the circuit. See the circuit board diagram . These symbols also are used to sometimes for when the circuit diagram is in two parts and the diagram won’t all fit on one page . It can also imply the use of a connector ( 3 pin connector in this case)….. so the two pieces can be separated from one another. But note the instruction say to keep the antenna/transformer ferrite bar as close to the circuit as possible. Finally , it is very important to make sure these connection to the antennea coil is made with the leads going to the right spot- don’t mix them up or cross them over- the lettering helps you keep this in mind. (A from the coil goes to A in the circuit, B to B , and C to C . Obvious I know, but keeping “tapped” coils phased the right way is very important

    17. In the text it is mentioned that the amplified signal is delivered to high impedance “ear phone” but in schematic a low impedance speaker is shown. Will anyone please clarify this?

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