Receiver for ask modulation

Thread Starter

Mohaamed Yousry

Joined Sep 23, 2017
14
hello , i'm trying to do ASK modulation , i've generated a carrier using the circuit attached below , i'm getting a 16 MHz , 3 v p-p sine wave at the emitter , i want to make a simple receiver for my transmitter , i've tried cascading 3 CE amplifiers like in the 2nd attached schematic , but i'm getting no output , how can i design a receiver for this circuit any help is appreciated .
 

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bertus

Joined Apr 5, 2008
20,226
Hello,

Did you check if the transmitter is giving any signal?
What are you using as antenna?
The receiver has no selectivity at all.
It will receive all frequencies that are in reach.

Bertus
 

Thread Starter

Mohaamed Yousry

Joined Sep 23, 2017
14
i think it is giving a signal because , my radio gets interference when my transmitter is powered , i'm using 2.5 m of copper wire as my antenna , i'm also connecting output of envelope detector to a LM358 comparator , but i'm getting no signal .
 

AlbertHall

Joined Jun 4, 2014
8,979
I'm pretty amazed that a three stage common emitter amplifier for 16MHz isn't just an oscillator. The fact that it isn't rather suggests the amplifier is seriously lacking gain for some reason.
 

Thread Starter

Mohaamed Yousry

Joined Sep 23, 2017
14

AlbertHall

Joined Jun 4, 2014
8,979
why would it oscillate ? i thought there needs to be positive feedback for a circuit to oscillate .
Yes, and unless that circuit was made with very careful routing and decoupling as it would have a gain around 1000, very little signal would need to be coupled back into the input to make another transmitter!
 

Zeeus

Joined Apr 17, 2019
482
hello , i'm trying to do ASK modulation , i've generated a carrier using the circuit attached below , i'm getting a 16 MHz , 3 v p-p sine wave at the emitter , i want to make a simple receiver for my transmitter , i've tried cascading 3 CE amplifiers like in the 2nd attached schematic , but i'm getting no output , how can i design a receiver for this circuit any help is appreciated .
https://forum.allaboutcircuits.com/threads/common-emitter-amplifier-design.159006/#post-1383947

lol..your ask still not working :(
 

DickCappels

Joined Aug 21, 2008
6,073
This one is sort of a glorified crystal set. Just replace the components in the resonant circuit with a LC pair that resonates at 16 MHz. The output is what is connected to the ATTINY12 -connect that to whatever high impedance load you like. Only build the circuit to the left of the ATTINY12. A 2N3904 should work fine at 16 MHz. An MPSH34 or KSP10 a little better because of lower input capacitance.

upload_2019-5-27_23-50-8.pngupload_2019-5-27_23-47-58.png

Tuning is tricky. I tuned this by spreading and compressing the inductor because I didn't have any suitable trimmer capacitor. It would be easier with a trimmer. I think the values shown put the center frequency near 100 MHz (that was along time ago!)

Consider changing your operating frequency to an ISM (Industrial, Scientific, Medical) band such as 13.56 MHz ±14 kHz or 26.957 to MHz 27.283 MHz where you will be unlikely to affect licenses services. Crystals for those bands are readily available and inexpensive.
 
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