Simple FM Radio (sure Works!)

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Orthopaedic Surgeon, Paragliding, Skiing, Digital electronics, Microcomputer lover.

Simple and powerful fm radio with easy to find parts

Step 1: Circuit

This is a regenerative Fm radio. Build very simple and easy to find parts. No special coils or uhf transistors.
Antenna catches fm waves, first transistor works as oscillator. R1, L1 and C1 determinates oscillation frequency. Internal freq and cathed freq overlaps and gets more power. Germanium diode detects audio freq. T2 and T3 works as audio ampflifier. Last condansator connected to jack is 45uf electrolytic con.

Note: if Fm broadcasts are weak or far away in your area, please use v2 circuit in troubleshooting step! Thank you.

Step 2: Work

Radio is very sensitive and selective.
Parts values in circuit is critical for oscillation and biasing of transistors.

You may use any kind of earphones. No high empedance earphones or crystal earphones needed.
C1 is 80-140 pf variable condensator. Once tunning with C1, you can fine tune with P1. Other potentiometer P2 is for volume control.

Step 3: Troubleshooting

1- There is not any voice: check all connections and transistor legs must be correct position.
2- There is a "hush" but no radio signals: check your battery it must be about 6-9v. If everything ok but still no signal, genly compress coil from laterals or get wider by your two hands.
3- Radio signal is not stable: in best receiving, hot glue your coil to fix in stable condition
Also if there is too many elegtromagnetical pollution in your area, it may be necessary to faraday isolation for your tuner part. To obtain this, aliminium foil coated cardboard may be good idea. Or you may try 2st version of circuit above. If u realise this 2nd version take p1 and c1 to middle position, move p1 till hear fm hush then search channels with c1.

Step 4: Putting in a Case

I build soldered version. Buyed a fuse box from a n electric warehouse. This is a wall fusebox.

Tips: if u wanna make soldered version make circuit on a wide area. Also coil lenght is very important to obtain fm bandwidh.

Step 5: Whats Next?

Version 3.0 without variable capacitor. Tuning with only 10k potentiometer.

Will be here shortly.

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    21 Discussions

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    SaifulH6

    5 months ago

    please see this diagram.

    I have all parts without T1,T2 ,can I change T1 and T2 ( BF422)?

    fm-receiver-circuit.jpg
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    SaifulH6

    5 months ago

    thanks a lot .greet work bro.

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    dhrovner

    6 months ago

    Hi. Have others made this? Is it sensitive (pulls in [tunes] many stations) and selective (clearly tunes in separate stations without overriding each other)?

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    AirraB

    1 year ago

    can i use a ordinary solid wire as a inductor?

    1 reply
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    mkpekerAirraB

    Reply 1 year ago

    Copper wire give better result

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    Matt Sawyer

    1 year ago

    Could you give me a list of materials please?

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    mkpekerAirraB

    Reply 1 year ago

    I used 1N34 but any of them works

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    naraina

    2 years ago

    very nice..................

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    laith mohamed

    2 years ago

    Very nice work its impressive to work radios and communications .

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    Being Engineers

    2 years ago

    Nicely done! Keep it up.

    I have also made this using TEA5767 Radio Module. Check it out.

    https://www.instructables.com/id/How-to-Make-FM-Receiver-Using-Arduino/

    1 reply
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    donny011

    2 years ago

    great build i like the fact that you have made it on breadboard so it can be copied by anyone helps beginners in electronics. there should be a section just for breadboard builds

    1 reply
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    mkpekerdonny011

    Reply 2 years ago

    Also i build soldered version. Its compact and pocket size :)

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    gm280

    2 years ago

    If the actual voltage does effect the operation, why not use a LDO 3.3 volt regulator to stabilize that issue? Then you could use most any type power and it would work over a longer period of time using battery power.

    2 replies
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    mkpekergm280

    Reply 2 years ago

    Thanx for your reply, circuit works fine between 2.5 -3.6v. I warned for over voltages like 6-9v. :)

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    mkpekermkpeker

    Reply 2 years ago

    I changed circuit that accepts 6-9 v power supply. Also more reliable and have fine tune

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    DIY radios man me a great intro circuit project. It's fun and it is something that you can actually use when you are done.