"Anthony Fremont" wrote in message
...
Pictures available in ABSE
The top trace (yellow) is taken between C4 and R2. The bottom trace
(cyan)
is taken at the base of the transistor. There is a switchercad file, but
the simulation will show allot of distortion that really isn't present in
the prototype circuit, because of lots of circuit capactance I suspect.
R1
was something I was playing with to try and tame the voltage across L1/C3
being applied to the base.


Hello all,

I was tinkering with this LC oscillator (Colpitts/Clapp) this weekend. I
arrived at the values of C1 and C2 empirically after starting with a
crystal
oscillator circuit. The values in the original circuit created a horrid
waveform that looked allot like the simulation. After much tinkering
around
and simulating, I come to the conclusion that getting a perfect waveform
is
nearly impossible, especially with big swing. It seems that the
transistor
likes to take a bite out of the right half of the peak of the wave.

What is the secret to beautiful waveforms? Do I need another LC resonator
on the output to fix it up? I mean, I'm getting a pretty nice wave now,
but
there is still some distortion that you can just see at the top of the
peaks
on the yellow trace.

How do you control the peak voltages of an LC resonattor without mangling
the waveform? The waveform at the junction of L1/C3 is of course quite
beautiful, how do I get it from there to the output? ;-)

I realize that I will need a buffer stage(s) before I can make any real
use
of the signal, but I want the input to the buffer to be as perfect as
possible.

The drive from the amplifier will inevitably be heavily clipped,
this is cuased by the need to have sufficient gain to start oscillation,
the clipping is the efffect of getting rid of the excess gain.

The current waveform is usually quite distorted,
usualy this is perfect to generate frequency multiples with a suitable tank.

There was a low distortion oscillator discussed in here not so long ago.
I think you do better with the inductor in the collector,
at least you need to take the output from the tuned circuit with a
capacitive divider,
but not via the transistor,
wich is easier with the inductor in the collector.

Also a jfet is ideal as it has a much softer clipping.

have you given up with the ne602 and the crystal ?

Colin =^.^=