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AM receiver schematic

AM Receiver Circuit

Application:

A small, simple AM receiver project with only 3 transistors. This circuit can pick up medium wave stations in your area.

Description:

It can use general purpose transistors, and in this example there are 3 BC109C transistors. The schematic and BOM show a 200µH inductor and a trimmer capacitor 150-500pF, though these parts can be salvaged from an old AM radio, to preserve the directional nature of a tuning coil, and an adjustment knob (plate capacitor) that work well for radio reception.

The 120k resistor is for regenerative feedback between the Q2 NPN transistor and the input to the tank circuit. The value of this resistor is important to the performance of the entire AM receiver. In fact, it may be better to replace the fixed value with a variable resistor paired with a fixed resistor to adjust the oscillation and sensitivity. All the connections should be short to minimize interference.

Performance will vary depending on stray capacitance in your layout, the inductor winding/core/length, etc. Changing values of some of the capacitors, or adding them, as well as a potentiometer in the feedback loop can help with the performance of the receiver. With such a small circuit that is affected so much by its construction and its environment, a lot of hand tuning and experimentation will be fun, instructive, and possibly necessary to make it work best.

[learn_more caption=”Click here for Parts List”]
RefDes Name Value Part Number Digi-Key Part Number Description
C1 VARIABLE 500pF GMC31100 GMC31100-ND CAP TRIMMER 150-500PF 175V TH
C2 NON POLARIZED 0.1uF C1005X5R1A104K050BA 445-1265-1-ND CAP CER 0.1UF 10V 10% X5R 0402
L1 AIR CORE 200uH CTX16-17309-R 513-1656-ND IND PFC 200UH 2.0A TOROID
Q1 NPN   ZTX1049ASTZ ZTX1049ASCT-ND TRANSISTOR NPN HIGH GAIN TO92-3
Q2 NPN   ZTX1049ASTZ ZTX1049ASCT-ND TRANSISTOR NPN HIGH GAIN TO92-3
Q3 NPN   ZTX1049ASTZ ZTX1049ASCT-ND TRANSISTOR NPN HIGH GAIN TO92-3
R2 RESISTOR 1K ERJ-14YJ102U P1.0KVCT-ND RES 1K OHM 1/2W 5% 1210 SMD
R3 RESISTOR 330 ERJ-14YJ331U P330VCT-ND RES 330 OHM 1/2W 5% 1210 SMD
C3 NON POLARIZED 0.1uF C1005X5R1A104K050BA 445-1265-1-ND CAP CER 0.1UF 10V 10% X5R 0402
R1 RESISTOR   ERJ-14YJ124U P120KVCT-ND RES 120K OHM 1/2W 5% 1210 SMD
R4 RESISTOR 560K ERJ-14YJ564U P560KVCT-ND RES 560K OHM 1/2W 5% 1210 SMD
R5 RESISTOR 10K ERJ-14YJ103U P10KVCT-ND RES 10K OHM 1/2W 5% 1210 SMD
C4 NON POLARIZED 0.1uF C1005X5R1A104K050BA 445-1265-1-ND CAP CER 0.1UF 10V 10% X5R 0402
[/learn_more]

Schematic of the receiver circuit

AM receiver schematic

10 Comments

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  • divya

    thanks for giving a good knowledge

  • nyni

    can u explain the function of each component in the circuit please!!! thank u !! ASAP

    • Larbi

      Hi John, I’m glad the mod was useful. I agree that cutnitg the tracks is tricky. It might be simpler to lift the emitter lead of the transistor and solder the resistor between it and ground. You could also probably remove the inductor instead of cutnitg the track on the input. Either way it is a fiddly job.I found replacing the display quite easy. I first straightened the two top clips with pliers then screwed the display in place and finally bent the clips again with a screwdriver. It looks like this is how it was assembled in the factory. Colin. G4EML.

  • mohammad

    hi
    may u say where the speaker’s place is?
    there is no sign in the schematic!

    • yash-verma28gmail-com

      the output side u connect the speaker and connect the other end of speaker to the negative terminal of battery……..

  • i think it is so good

    for ten years ago i try to made good radio but i cannt help me please to send me good circuits to do that

  • John John Florence

    Hey, i only have some questions, and all of them start with WHY? would you be kind enough to explain me how did you take the values from all the c1 c2, r1, r2, etc. Because it is not enough for me to see the circuit i want to know why and how it works
    THANKS
    JJF

    • Majlinda

      Hi all, well I tried the mod out on my uv-5re and while it did increase the devaition I now have something strange. while the tdr(dual band mode) is on I am getting a strange pulsating noise. it isn’t in the rx as the squelch is kicked in and the signal indicator is out. It does stop if I opt out of dual band mode. It also is producing static from the unit after you tx and I must hit the monitor button to clear it up. It is similar to the above mentioned issue but without the pulsating. I left L44 in place and cut the trace as illistrated, And lifted the leg of Q17 instead of cutting the ground trace and installed the 470 ohm SMD capacitor from the leg to ground. I am not sure if it is nessassary to cut the ground trace or not. I am curious if anyone else has seen this issue?Thank you in advance,M.S.

  • sahar paware

    looks like really applicable.
    i’m going to try this today itself. its nice one.

  • José Domínguez

    Me gustaría que me enviasen las medidas, número de espiras y diámetro del hilo (AWG) esmaltado para construir la bobina de 200 uH.

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