Armstrong oscillator won't resonate

[StoppTidigare]

ads simulation hartley .dsn oscilator

Hi, I wonder if somebody can help me with an oscillator circuit.

1. Is it possible to simulate oscillation with the SPICE3f5-engine? Or do one need a Harmonic Balance -code ? (Just, heard of it, don't know what it does. Has to do something with the problems encounteed in oscillator-simulation).

2. If possible to simulate how do I increase the feedback-voltage from collector to base without compromising the 180 +180 degree phase shift (collector output + transformer)

Kindest regards,
StoppTidigare

Attaching a proteus simulation file

 

[VSWR]

SPICE is useful for oscillator simulation. What is the oscillation frequency? A circuit diagram would help (jpeg, gif, pdf etc), your RAR-file only contains a DSN-file.

 

[LvW]

1.) Oscillator circuits can always be simulated with transient analysis. In order to keep the simulation time within limits it sometimes makes sense to give a capacitor an initial voltage.
2.) I recommend to you not to post a simulation file, but instead a pdf or jepg format to show the circuitry.

 

[StoppTidigare]

Thanks for the responce good friends.

Here is a picture with the Dc-operating point values on the virtual measurements.

/StoppTidigare

 

[webdog]

Those resistor values seems a bit high... 1 Megohm in bias for a bipolar transistor?? and 20 kohm in collector... I would try to run a tad higher Icq, but maybe you did shoot for ultra low current??

 

[Eugen_E]

It's a superregenerative receiver? In this case simulation will be dificult and long, needing at least a few quench cycles.
What frequency? C1 is too big for RF, also C3 value is too high. What kind of transformer do you use, the winding inductance should be in the µH - nH range, not an iron core transformer.

If it's only oscillator, not receiver, the R1 lead going to LC tank should be bypassed with a 10nF capacitor. Also, lower values for resistors.

 

[LvW]

What is the purpose of V2 and C1 ?

 

[StoppTidigare]

Thank you friends!
The V1 source was thought to be needed to kickstart the oscillation. Thought I needed something equivalent to noise to get the party started.

It must be the case that an oscillator circuit does not need a simulated noise source to get started in simulatio, since it comes inderectly from numerical integration errors.

I got these values forn the transformer
{LP=0.1uH}
{LS=0.1uH}
{M=1.0} //coupling facxtor
{RP=1m}//Ohms
{RS=1m}//Ohms

I just want it to oscillate with a frequency whats so ever, its not an advanced design. I am not an rf-engineer. Just helping a friend that teaches radio in a military school.
The oscillator is a part of a reactance modulator that is to be simulated and explained to the students.

I tried to take the transformer connection from the upper connection instead of the
lower. In the simulation it does not matter(1?!), only the load node resonates, neither the base or the collector. ????

Can you guys give me some rules of thumb for the proper bias ?

Should U_ce be 30% of supply voltage U_Rc= 40% and U_Re=30% ?
Or what do you people usally use?

Kindest regards,
StoppTidigare

 

[Eugen_E]

Eliminate R1,C1, V2, put a bypass cap from R4-transformer junction to ground.
Select transformer winding inductance and C3 so that reactance is in the range of 50-500 ohm at the resonant frequency, egg. C3=100pF, L=10uH. Bias depends on oscillator, needed amplification you should use 0.5-3mA current, and maximum voltage swing. For HF oscillators, simulate for at least 50-100us.

Classic Hartley and Colpitts oscillators are more common, and easier to do in practice, with no transformer.

 

[vfone]

Use the new resitor bias values and the new added decoupling capacitors and it will work.

 

[FvM]

It must be the case that an oscillator circuit does not need a simulated noise source to get started in simulatio, since it comes inderectly from numerical integration errors.

If you are basically interested in simulating a circuit rather than simulator research, I wouldn't make such assumptions. A current pulse as starter has the advantage of not affecting the circuit after the stimulation has ended. And it also reveals insufficient positive feedback of an oscillator by showing a decreasing oscillation.