"Paul Keinanen" wrote in message
...
On Sun, 06 Jun 2004 17:59:00 -0500, Ed Bailen wrote:

The last issue of QST had a short article on the CircuitMaker Student
edition circuit design package. I downloaded it and spent several
hours trying various oscillator designs (including the phase shift
oscillator discussed in the same issue of QST). I couldn't get any of
the designs to oscillate! I was mainly trying Colpitts oscillators.

Typically, an oscillator is just a noise amplifier with some frequency
selective feedback. In a real oscillator, there is always some wide
band thermal noise present, which is amplified, some selected
frequencies are circulated back to the input and reamplified and so
on. Finally, there is going to be a narrow spectral line and a wide
band noise floor due to the thermal noise, assuming of course that the
phase, amplification and feedback loss conditions are correct.

If the simulator does not simulate the thermal noise inherent in all
resistors and semiconductors in temperatures above absolute zero, it
is not very likely that the design would oscillate. Inject a very low
level wide band noise into the amplifying stage and the oscillation
should start. However, I have never seen the CircuitMaker or how to
generate a wide band noise signal with it.

Injecting a pulse usually works with SPICE, I've found.

Leon

I have found that that generating a narrow pulse with a current source works
well for me. The oscillator gets going rather quickly because the narrow
pulse has a wide frequency spectrum and since the ideal current source is an
open it doesn't impact the circuit operation.

Darrell VE6DWB

"Paul Keinanen" wrote in message
...
On Sun, 06 Jun 2004 17:59:00 -0500, Ed Bailen wrote:

The last issue of QST had a short article on the CircuitMaker Student
edition circuit design package. I downloaded it and spent several
hours trying various oscillator designs (including the phase shift
oscillator discussed in the same issue of QST). I couldn't get any of
the designs to oscillate! I was mainly trying Colpitts oscillators.

Typically, an oscillator is just a noise amplifier with some frequency
selective feedback. In a real oscillator, there is always some wide
band thermal noise present, which is amplified, some selected
frequencies are circulated back to the input and reamplified and so
on. Finally, there is going to be a narrow spectral line and a wide
band noise floor due to the thermal noise, assuming of course that the
phase, amplification and feedback loss conditions are correct.

If the simulator does not simulate the thermal noise inherent in all
resistors and semiconductors in temperatures above absolute zero, it
is not very likely that the design would oscillate. Inject a very low
level wide band noise into the amplifying stage and the oscillation
should start. However, I have never seen the CircuitMaker or how to
generate a wide band noise signal with it.

Paul OH3LWR

"Ed Bailen" wrote in message
news
The last issue of QST had a short article on the CircuitMaker Student
edition circuit design package. I downloaded it and spent several
hours trying various oscillator designs (including the phase shift
oscillator discussed in the same issue of QST). I couldn't get any of
the designs to oscillate! I was mainly trying Colpitts oscillators.

Has anyone else tried designing oscillatos with this application?

Thanks,
Ed Bailen


Are you sure you set the simulation time long enough for the oscillator to
get started ?

On Sun, 06 Jun 2004 17:59:00 -0500, Ed Bailen wrote:

The last issue of QST had a short article on the CircuitMaker Student
edition circuit design package. I downloaded it and spent several
hours trying various oscillator designs (including the phase shift
oscillator discussed in the same issue of QST). I couldn't get any of
the designs to oscillate! I was mainly trying Colpitts oscillators.

Has anyone else tried designing oscillatos with this application?

Ed, I don't have any experience of CircuitMaker but I do have trouble with
getting oscillators to oscillate on other simulation packages. This is
inherent in the design of the simulators in that they will deliberately try
to stabilise the circuit and stop the oscillation from taking off!

If you have an option in there to 'skip initial transient solution' or
something similar, it's good to check the box and bypass it - this is the
thing that tries to DC stabilise the circuit. From there, it relies on
noise to get the oscillator start and if there isn't any, it won't...

--
Duncan Munro M0KGK
http://amateur.duncanamps.com/
BOF #023 FISTS #10815

You need to set an "Initial Condition" (place the I.C. box from parts) for it
to begin oscillating :-)

--
Gregg
*It's probably useful, even if it can't be SPICE'd*
http://geek.scorpiorising.ca

On Sun, 06 Jun 2004 17:59:00 -0500, Ed Bailen wrote:

The last issue of QST had a short article on the CircuitMaker Student
edition circuit design package. I downloaded it and spent several
hours trying various oscillator designs (including the phase shift
oscillator discussed in the same issue of QST). I couldn't get any of
the designs to oscillate! I was mainly trying Colpitts oscillators.

Typically, an oscillator is just a noise amplifier with some frequency
selective feedback. In a real oscillator, there is always some wide
band thermal noise present, which is amplified, some selected
frequencies are circulated back to the input and reamplified and so
on. Finally, there is going to be a narrow spectral line and a wide
band noise floor due to the thermal noise, assuming of course that the
phase, amplification and feedback loss conditions are correct.

If the simulator does not simulate the thermal noise inherent in all
resistors and semiconductors in temperatures above absolute zero, it
is not very likely that the design would oscillate. Inject a very low
level wide band noise into the amplifying stage and the oscillation
should start. However, I have never seen the CircuitMaker or how to
generate a wide band noise signal with it.

Paul OH3LWR

"Ed Bailen" wrote in message
news
The last issue of QST had a short article on the CircuitMaker Student
edition circuit design package. I downloaded it and spent several
hours trying various oscillator designs (including the phase shift
oscillator discussed in the same issue of QST). I couldn't get any of
the designs to oscillate! I was mainly trying Colpitts oscillators.

Has anyone else tried designing oscillatos with this application?

Thanks,
Ed Bailen


Are you sure you set the simulation time long enough for the oscillator to
get started ?

Hi,
Yes, I have tried doing just that, and it works after a fashion, but not
always and not usually very well.

The most recent ARRL handbook (2004) says that very special and expensive
software is needed to simulate oscillators properly.

73 de k1jhj

"Ed Bailen" wrote in message
news
The last issue of QST had a short article on the CircuitMaker Student
edition circuit design package. I downloaded it and spent several
hours trying various oscillator designs (including the phase shift
oscillator discussed in the same issue of QST). I couldn't get any of
the designs to oscillate! I was mainly trying Colpitts oscillators.

Has anyone else tried designing oscillatos with this application?

Thanks,
Ed Bailen

"Ed Bailen" wrote in message
news
The last issue of QST had a short article on the CircuitMaker Student
edition circuit design package. I downloaded it and spent several
hours trying various oscillator designs (including the phase shift
oscillator discussed in the same issue of QST). I couldn't get any of
the designs to oscillate! I was mainly trying Colpitts oscillators.

Has anyone else tried designing oscillatos with this application?

Thanks,
Ed Bailen
=====================================

Not good.

I hope that you will notify ARRL (or have) about this.

If there are serious deficiencies in the software (regardless of whether
it is free or not), then possible users should be made aware of them.

Thanks for letting me know, just in case I try to use it.

Jack W8RAG

"Ed Bailen" wrote in message
news
The last issue of QST had a short article on the CircuitMaker Student
edition circuit design package. I downloaded it and spent several
hours trying various oscillator designs (including the phase shift
oscillator discussed in the same issue of QST). I couldn't get any of
the designs to oscillate! I was mainly trying Colpitts oscillators.

Has anyone else tried designing oscillatos with this application?

Thanks,
Ed Bailen


I have a Colpitts oscillator running ok in Circuit Maker Student V6.2c.
I can send you the file if you'd like. (small, about 13 kb)