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FM radio receiver

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audioguru said:
By touching a 22k resistor across the existing 33k resistor, you instantly change their total value to only 13.2k to see if it helps with the lower resistance.
I've tried using a 10K...
Then the one transistor FM radio will pickup nothing.
What did you expect it to pickup?
I didn't know that it can only picks up signal from nearby station. What is the max range of this type of receiver? Can I use it with your mod4 FM transmitter?

Thanks..
 
redserpentone said:
That q1 will give about 5 to 7 bB gain

Another Q(2) at the node of r1, r5, r7, c4 will get you another 5 dB
this will get you a radio receiver, not a boom box, but a real RX
No it doesn't and no it won't.
This is a crappy super-regenerative "radio" and its transistor oscillates at the RF frequency then stops then oscillates then stops at an ultrasonic rate. It is supposed to average its operation at a very high gain just before it oscillates.

The node doesn't have RF, it has audio.

An RF amplifier might be added to the input but this crappy circuit didn't even have an input!
 
bananasiong said:
I didn't know that it can only picks up signal from nearby station. What is the max range of this type of receiver? Can I use it with your mod4 FM transmitter?
A real FM radio has many transistors, ICs and tuned circuits for good sensitivity and selectivity. A real FM radio has an FM detector.
This one has only one transistor and one tuned circuit. It doesn't have an FM detector so you must tune it to the side of an FM station then its sensitivity is reduced.

The frequencies of the FM band are VHF that travel in a straight line. The curve of the earth blocks the signal at about 60km but farther if it travels between two mountain tops.

My Mod4 FM transmitter was picked up by my very good home stereo FM tuner and my very good car radio at 2km away when nothing was between. The range to my Sony Walkman FM radio was about 1/2km. Houses and trees blocked the signal.

Your super-regen "radio" might pick it up across the street.
 
Nevermine, even it is less than 50 meter.
So, my next job is to make your Mod4 and test it with a normal radio, then test both the tx and rx. Thanks!

*For the coil of your Mod4, can I use the one same as what I'm using in my crappy 'radio'? It is 6 turns, 8-9mm diameter, stretched until the length is less than 1.5cm.
And, if I want to ask somemore about Mod4, should I post here? Or post at Electronics Projects?
 
bananasiong said:
*For the coil of your Mod4, can I use the one same as what I'm using in my crappy 'radio'? It is 6 turns, 8-9mm diameter, stretched until the length is less than 1.5cm.
My circuit might not work with the coil stretched out so far. Mine is compact.
Is your FM band from 88MHz to 108MHz like mine? Some countries are different.

And, if I want to ask somemore about Mod4, should I post here? Or post at Electronics Projects?
Start a new thread.
 
audioguru said:
My circuit might not work with the coil stretched out so far. Mine is compact.
Is your FM band from 88MHz to 108MHz like mine? Some countries are different.
But it is not stretched much. Before stretching (each turn is in side by side to each other) it is about 1.1cm of the length, after stretching, it is less than 1.5cm, around 1.4cm only.
And, yes, from 88MHz to 108MHz like yours.

Thanks.
 
can you elaborate what is that mean by "The center tap must be exactly center? Because I made a 5 turns coil, if exact center needed, I have to connect a jumper from the top of the coil." Does it mean i have to put wire on top of the coil (which connected to 1k ohm) and connect it to the centre of the coil (which is the part i put the C3 leg on)? im tired doing this circuit, it doesnt give me any sound out! dont know what is my prob. i using the exactly the same component as in the schematic. and check my circuit connection hundred times. :-(
 
can you elaborate what is that mean by "The center tap must be exactly center? Because I made a 5 turns coil, if exact center needed, I have to connect a jumper from the top of the coil." Does it mean i have to put wire on top of the coil (which connected to 1k ohm) and connect it to the centre of the coil (which is the part i put the C3 leg on)?
Make the coil with 6 turns then the center tap is on top. Stretch the turns apart a little to reduce the inductance.

im tired doing this circuit, it doesnt give me any sound out! dont know what is my prob. i using the exactly the same component as in the schematic. and check my circuit connection hundred times. :-(

Are you making this garbage-quality single transistor FM "radio"? It won't work if you make it on a breadboard because the 100MHz frequency is much too high and the very high stray capacitances and inductances of the breadboard cause too many problems. It must be made on a compact pcb with an RF design.
 
thanks for the information!. will not wasting my time anymore building this circuit.
btw, do you have fm stereo receiver schematic that i can build on the breadboard?
 
thanks for the information!. will not wasting my time anymore building this circuit.
btw, do you have fm stereo receiver schematic that i can build on the breadboard?

REPEAT: 100MHz is a frequency that is much too high to use a breadboard. A compact pcb is needed.
I wouldn't use a breadboard for a 1MHz AM radio circuit.
 
REPEAT: 100MHz is a frequency that is much too high to use a breadboard. A compact pcb is needed.
I wouldn't use a breadboard for a 1MHz AM radio circuit.


ops.sorry. my bad. anyway, can i know what is this circuit doing actually ? why they are grounding most of the component? is it for filter? does this circuit contain any amplifier?
 
can i know what is this circuit doing actually ? why they are grounding most of the component? is it for filter? does this circuit contain any amplifier?
The circuits on the first page of this thread are called Super-Regenerative Radio circuits. Look for a description in Google.
It uses a TL431 adjustable shunt voltage regulator for an audio amplifier to drive a high impedance earphone.
The circuit is extremely simple so it is easily overloaded by strong local stations, produces audio distortion and makes interference noises.
 
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