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

http://imgur.com/a/j4Q3vM2

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

 

hi 2k4
Welcome to AAC,
Try this with actual transistor types.

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hi 2k4,
Unzip and install the micelectret model
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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

 

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:

 

Hi,
Note dB Sound Levels , example.
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I m unable to configure the mic part correctly

check this out:

 

hi,
Replace the 68k, with a 2k2
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I tried replacing 68k with 2k2 but circuit doesn't produce oscillations

 

Hi 2k4,
Checking the response plot shows the peak frequency is about 75MegaHz
Will check the non oscillation problem.
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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.
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Try increasing the 470R to 1k, set L1=50n, and Skip initial operating point solution.

 

hi 2k4,
Those voltages shown on the original circuit are incorrect, so that makes me suspect that there are other errors in that diagram.
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See

 

Hi,
The TS is using LTSpice not QSpice.

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Hi,
The TS is using LTSpice not QSpice.

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I know, but I showed the advantage of Qspice - there is no need to count inductance and it counts faster.

 

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,
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Any initial modulation seems to block the oscillator from starting up.

It starts up, with initial modulation, using the post #12 hacks.

 

Hi Alec,
It's a pity you did not post the plot from post #12
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I assumed anyone interested would have run the sim for themselves.