Simulating a RF transmitter bug in LTspice

Thread Starter

Dinesh_2k4

Joined Aug 18, 2022
23
hey guys i,m new to this forum and Lt spice
I am planning on building a FM bug using hardware,
i am trying to simulate this circuit using LTspice

In simulation i am replacing the microphone with a voltage source of 10mV and 2kHz then removing 68k resistor.
simulation file is attched.Kindly assist me with this guys..

I get the amplified version of signal from the first stage but the oscillations of around 88-108MHz are not being produced from the second transistor
 

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Thread Starter

Dinesh_2k4

Joined Aug 18, 2022
23
Thanks a lot!!! ericcgibbs
its working fine right now
I was planning on using a BC547to build the circuit and when i changed the 2N2222 to BC547B its still working fine!!

I have a doubt the output voltage is around 16-18 while the supply is just 9V is it normal? (just due to capacitors) can u plese explain
 

Thread Starter

Dinesh_2k4

Joined Aug 18, 2022
23
Thanks bro I have installed the MIC library too!!
what are theparameters in that mic module?
frec indicates frequency
what does "dbSPL" indicate?

check this out:
 

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Last edited:

ericgibbs

Joined Jan 29, 2010
18,864
Hi 2k4,
I cannot make it run correctly, sometimes it will, but it takes ages.

I suggest you test with the 1kHz voltage source and not the mic.
E
 

ericgibbs

Joined Jan 29, 2010
18,864
hi 2k4,
Those voltages shown on the original circuit are incorrect, so that makes me suspect that there are other errors in that diagram.
E
 

ericgibbs

Joined Jan 29, 2010
18,864
hi 2k4
I can get the oscillator to start up, providing I delay the modulation.
Any initial modulation seems to block the oscillator from starting up.
The simulation takes minutes to run,
E
EG57_ 1503.png
 
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