Trash parts FM receiver, no antenna required. The circuit used in this video (tuning depends on parasitics, tuning C was here 10pf and output C was 100nf): www.niksula.cs.hut.fi You can also try to make the resonant circuit with the inductor at the transistor base instead of the collector. I used 2N3904 transistor. Circuit that is easier to get working: www.niksula.cs.hut.fi Tuned to around 100mhz (or maybe some harmonic). Essentially consists of 1 transistor, 1 resistor, 1 capacitor and some wire (coils). The idea in the first schematic is to make a positive feedback and an oscillator by coupling the two coils. The second schematic doesn’t depends on that. Now why does this works as a receiver? Nonlinearities in the oscillator cause it to multiply the incoming signal with it’s own oscillations extracting the signal (although it should be filtered to remove all other frequency components except audio frequencies). The same circuit could be used in reverse as a transmitter although it should be amplified significantly and the signal filtered since the spectral purity would be awful. The reverse will work because the transistor junction capacitance is a function of the bias voltage resulting in different oscillation frequency and so archiving the frequency modulation. It also causes some amplitude modulation which can be removed by amplification. Tuning is done by deforming the coil and/or using the screwdriver as a slide. Surprisingly it works and sound quality isn’t too …
Mystery reggen – simple(st) FM receiver?
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{ 25 comments… read them below or add one }
Should be ok. Any small signal transistor with some gain at 100MHz should work. Datasheets will tell. Some parameters might chance the optimal values, but the circuit isn’t too hifi anyway.
can i use bc548/148
Just trial and error. The black thing is supposed to be an antenna, but after this video I tried without it and it worked just as well.
Sometimes I use a frequency counter to get the oscillations tuned to approximately correct frequency, but it’s not that necessary.
How did you make the coils? Did you just try to make bigger ones or adjust them until it worked? and is that black thing sticking up an antenna of some sort? just wondering because it says that no antenna is required in the information.
Now to amplify the signal from an FM transmitter.
hi nice work… CAN I ADD a bigger coil and a diode and try to make a powered crystal radio ???? im looking for some way to power a crystal radio so I can use it without a ground connection.
this is very simple!
Possibly, I didn’t try, the output without an amp is pretty weak, but maybe it’s still strong enough to be heard with those crystal earbuds.
lol wow. can you listen to the output with like crystal radio type earbuds?
Neat
This I must build some day. 
I changed my ISP, not updated.
There was an unfortunate loss of files when I updated my ISP. However I have updated the links for this video now. They should work.
hi i cant open circuit diagram page can U send me circuit diagram please!
use a preamp to ampliify the af sounds! take a view on google a condenser mike preamp!
_Youtube description_ has a link to the schematic (push “more info”) and read the description, it will also give you a rough idea of how this is supposed to work.
Tuning capacitor is 10pF, transistor is 2N3904, bias resistor is 10k, output capacitor 100nF. Inductors are trial and error so just what you see in the video. None of the values are exact as your breadboard is a major part of the capacitance at these frequencies.
hi i ‘m sorry to say but i accidentally missed the details u sent ..can u resend me the circuit diagram of the simple fm RX plus the component values? i ‘ll appreciate it so much.
I’ve heard that it can also detect SSB when feedback is properly adjusted (so that the device oscillates and creates the missing carrier), but I have not verified this.
The circuit can also be viewed as a negative resistance amplifier where adjusting the feedback will determine the gain and if very high it will just make it an oscillator.
It can detect both. The frequency range is determined by the resonant circuit and can be anything within reason. I have verified with a signal generator that it does detect 100MHz FM signals. However the demodulation is more efficient with AM than FM.
Mostly it’s just an RF amplifier which also happens to demodulate the signal to some extent due to transistor nonlinearity.
is it really FM or AM??
Schematic and values are listed in the description along with some explanation although values are only in the general direction of what might work. The output signal should also be amplified as it is quite weak.
wooooooow that’s exactly what i ‘ve been lookin’ for ….. can i get the circuit diagram of this device..including the components plus their values ?….pleeeeeeease (decod31).
this song is so nostalgic, reminds me of the good old 90′s
It isn’t a mystery, this effect appears in all the amplifiers. Try to plug a long wire in an amplifier input and turn on the volume… touching the wire you’ll fill better the effect cause your body will be the antenna. YOU’LL HEAR THE RADIO. Now, he’s doing the same, ’cause the transistor is an amplifier and he’s also amplifying the transistor output with another amplifier.
The capacitor works with the piece of wire doing a defined resonance helping the radio reception.
lol. spice girls on the radio. i was 10 when they were a big hit.
explaime me please
i like to learn.