colin wrote:
"Anthony Fremont" wrote in message

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.

Ok, I guess that makes sense. You want plenty of gain, and with plenty of
gain comes clipping.

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


This would be for overtone oscillators?

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.

I found an MPF102 here and doctored up the circuit for it, much nicer
waveform. Much less voltage in the tank though, but it starts fine. This
is fun. ;-) I'm going to wind myself a lower inductance coil and see if I
can get it to run at 10MHz.

have you given up with the ne602 and the crystal ?

Just side tracked for now. ;-) The crystal is kinda restrictive, but I'm
going back to the 602 soon. I'm going to try to make a single conversion
superhet for WWV reception at 10MHz. I have some IF cans of various colors,
so I'm sure I have some for 455kHz. If I can make an LO that will stay
within 1kc of 9.545 at room temperature, I'm going to go with it to beat
against WWV.

Right now my prototype circuit is drifting back and forth over a 1.5kc range
while running at 4MHz. I'm using ordinary ceramic caps to set the
frequency, and everything is on a breadboard. The 2kc drift seems to
coincide with the air conditioning induced temperature changes in the room.
Plenty of room for improvement on that. ;-)

I just wound another coil for 5uH. Things get more picky as the frequency
goes up, but I got it running at 9.5Mhz and it's staying within a few kcs.
Interesting stuff. :-)