On 9/30/2010 12:43 PM, Alan Melia wrote:
Mark to my inexpert eye that doesnt look like a very good overtone
oscillator but I appreciate that it is slimmed down to keep the weight and
size down, I can see why it is touchy. There is nothing to make the
oscillator degenerate at the crystal fundamental. In fact it looks like a
Pierce with a tuned circuit in the anode. If it goes off at the overtone my
guess is that it by luck! But there are more clever people than me in this
Group who may be more useful to you.
I agree completely. What I have found to work is:
Build a free running Colpitts oscillator and get it tuned to the
frequency you want. Then, insert the crystal in series with the
emitter. Insert the load in series with the collector. Obviously,
this is easiest if a "grounded collector" topology is used. I used this
for many high volume crystal oscillators and they just worked, period.
No tweaking.
Rick Karlquist N6RK
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