FM transmitter Audioguru

rimEP

New Member

• May 31, 2017

• #1

Hello,
I've been trying to simulate Audioguru's FM transmitter with Proteus then with LT spice but I have encountered numerous problems. First of all, this is my first try with LT spice. Secondly I can't find the LM2931a regulator. Also I don't know how to run the simulation because I always get a blank diagram as an output.
I joined my draft on Lt spice and Audioguru's model picture to this message.
I will be very grateful if you could help me.

 

Attachments

• Draft1.asc

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• FM tx mod4 pic and schematic.jpg

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ronsimpson

Well-Known Member

Most Helpful Member

• May 31, 2017

• #2

I do not have it working but some of the errors are fixed.
I added a 5V and a 9V voltage(s)
There was a resistor with out value.
I fixed the two capacitors at 30pF.

No time now. Maybe some one can make it work.

 

Attachments

• FM-1.asc

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rimEP

New Member

• May 31, 2017

• #3

Thank you so much RonSimpson.

 

ronsimpson

Well-Known Member

Most Helpful Member

• May 31, 2017

• #4

R5 is also wrong. (audio problem)
I do not see any hint of RF. (rf problem)

 

ronsimpson

Well-Known Member

Most Helpful Member

• May 31, 2017

• #5

Right click on each inductor.
Clear all windows except inductance. 1nH The parallel resistance should be blank. The parallel cap should be 1pF or blank.

 

rimEP

New Member

• May 31, 2017

• #6

like this ?

 

Attachments

• FM-1.asc

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audioguru

Well-Known Member

Most Helpful Member

• May 31, 2017

• #7

The monsterous very high power inductors you used in your sim do nothing at very high radio frequencies. I made the inductors myself and they work perfectly.

Here is my sim of the RF circuit with its parts tweaked to work the best:

 

Attachments

• FM transmitter tweaked.png

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rimEP

New Member

• May 31, 2017

• #8

I erased all the other values in my components. How can I define what other values to put?

 

audioguru

Well-Known Member

Most Helpful Member

• May 31, 2017

• #9

Your TRAN command does not delay the start time to save data so the oscillator is not even oscillating yet when your sim stops. The oscillation is good after a start delay of about 4000ns, look at the TRAN command on my sim.

Here is my TRAN command:

 

Attachments

• FM tx TRAN command.png

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